PNMT
Phenylethanolamine N-methyltransferase (EC 2.1.1.28) (PNMTase) (Noradrenaline N-methyltransferase) [PENT]
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Catecholamines, which are physiologically important neurotransmitters and hormones, apparently decrease in the brain and plasma as some species age. Because this observation has engendered controversy, we used mice to investigate whether age-related changes occur in adrenal catecholamine levels and in the expression of catecholamine synthetic enzymes. Adrenal glands were collected from male C57BL/6NCr mice at the ages of 6, 12 and 24 months. Catecholamines, such as dopamine (DA), noradrenaline (NA) and adrenaline (AD) from those glands, were measured by using a highly sensitive liquid chromatographic method with peroxyoxalate chemiluminescence reaction detection. Tyrosine hydroxylase (TH), dopa decarboxylase, dopamine beta hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) mRNA expression levels were measured by quantitative real-time polymerase chain reaction. Although DA levels in the adrenals of 24-month-old mice were higher than in 6- and 12-month-old mice, the AD content decreased with age. In such mice, the ratio of DA to NA at 24 months was lower than at 12 months, and the ratio of NA to AD content at 24 months was significantly lower than at 6 months. The mRNA expression ratios in TH, DBH and PNMT in 24-month-old mice were all lower than in 12-month-old mice. These results strongly suggest that catecholamine synthesis, in general, declines with aging in the adrenal glands of mice and that AD, in particular, undergoes a significant decrease with advancing age.
MeSH Terms
- Adrenal Glands
- Aging
- Animals
- Body Weight
- Chromatography, Liquid
- Dopa Decarboxylase
- Dopamine
- Dopamine beta-Hydroxylase
- Epinephrine
- Luminescence
- Luminescent Agents
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred Strains
- Neurotransmitter Agents
- Norepinephrine
- Organ Size
- Oxalates
- Phenylethanolamine N-Methyltransferase
- RNA, Messenger
- Real-Time Polymerase Chain Reaction
- Tyrosine 3-Monooxygenase
Adolescent alcohol exposure (AAE) may exert long-term effects on the adult brain. Here, we tested the hypothesis that the brain regions affected include the rat hypothalamic-pituitary-adrenal (HPA) axis. Specifically, we examined the consequences of AAE [postnatal days (PND) 28-42] on the HPA axis-related brain circuitry of male rats challenged with an intragastric (ig) administration of alcohol in young adulthood (PND 61-62). Adolescent rats were exposed to alcohol vapors, while controls did not receive the drug. The mean blood alcohol level in adolescence on PND 40 was 212.8±5.7 mg %. Using immunohistochemistry and in situ hybridization procedures, we measured signals for c-fos and corticotropin releasing factor (CRF) in the paraventricular nucleus (PVN) of the hypothalamus, as well as signals for c-fos and phenylethanolamine N-methyltransferase (PNMT) in the adrenergic brain stem regions (C1 and C2). PVN CRF mRNA expression was significantly blunted in AAE rats tested at PND 61-62, compared to their controls. These animals also displayed a significant increase in the mean number of PNMT-ir cells/brain stem section in the C2 area. Collectively, these results suggest that exposure to alcohol vapors during adolescence exerts long-term effects on the ability of the PVN to mount a response to an acute alcohol administration in young adulthood, possibly mediated by medullary catecholamine input to the PVN.
MeSH Terms
- Aging
- Alcohol-Induced Disorders, Nervous System
- Animals
- Brain Stem
- Disease Models, Animal
- Ethanol
- Hypothalamo-Hypophyseal System
- Male
- Rats
- Rats, Sprague-Dawley
- Stress, Psychological
The ontogeny of the catecholaminergic system of the median eminence (ME) arcuate nucleus (ARC) complex (MEARC) has been studied in various animal species but so far, nothing has been learnt about the development of catecholaminergic structures in the porcine MEARC. To study this problem the hypothalami from animals at different ages (six groups) were collected. Nerve structures immunoreactive (R) for the substances studied [(tyrosine hydroylase (TH), dopamine beta-hydroxylase (D(beta)H) and phenylethanoloamine-N-metylthransferase (PNMT)] were found in the pigs at different age periods. In MEARC, TH-IR structures appeared before the 70th day of foetal life, D(beta)H-IR before the 10th week of postnatal life and PNMT-IR only in sexually mature sows.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Arcuate Nucleus of Hypothalamus
- Axons
- Catecholamines
- Cell Differentiation
- Dopamine beta-Hydroxylase
- Female
- Fetus
- Hypothalamo-Hypophyseal System
- Immunohistochemistry
- Median Eminence
- Neurons
- Phenylethanolamine N-Methyltransferase
- Sus scrofa
- Tyrosine 3-Monooxygenase
The aim of this investigation was to assess whether in teleosts, as in mammals, nitric oxide (NO) is involved in the regulation of cellular activity in the adrenal homolog. Larval and juvenile stages of the rainbow trout, Oncorhynchus mykiss, were used, in which the adrenal homolog consists of chromaffin adrenergic and interrenal steroidogenic cells localized mainly in the head kidney where there are also ganglion cells and nerve fibres that innervate the gland. In 12-month-old juveniles, the immunohistochemical reaction for neuronal nitric oxide synthase (nNOS), which catalyzes the synthesis of NO, revealed the presence of this enzyme in some nerve fibres and ganglion cells and only rarely in chromaffin cells. The latter are identified by the immunohistochemical reaction for tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT). In larvae at 27 days postfertilization, numerous cells dispersed in the head kidney are nNOS positive, whereas the TH and PNMT positive cells are very rare. At hatching (31 days postfertilization), the positivity for nNOS in the cells of the head kidney disappears and reappears at 60 days posthatching in some nerve cells and fibres. These results suggest an involvement of NO in the regulation of adrenal function as in mammals and the nature of nNOS positive cells present in the head kidney of larvae of 27 days is discussed.
MeSH Terms
- Aging
- Animals
- Chromaffin Cells
- Epinephrine
- Female
- Immunohistochemistry
- Kidney
- Larva
- Male
- Nitric Oxide Synthase
- Nitric Oxide Synthase Type I
- Norepinephrine
- Oncorhynchus mykiss
- Phenylethanolamine N-Methyltransferase
- Tyrosine 3-Monooxygenase
Adrenergic and noradrenergic neural projections to the paraventricular nucleus of the hypothalamus (PVN) contribute importantly to viscerosensory modulation of pituitary hormone secretion. Immaturity of ascending catecholamine pathways may partially underlie the documented hyporesponsiveness of PVN neurosecretory cells to certain interoceptive stimuli in rats during the first few weeks of postnatal development. To explore this possibility, the present study compared the distribution and number of dopamine-beta-hydroxylase (DBH)- and phenylethanolamine-N-methyltransferase (PNMT)-positive neurons projecting to the PVN in newborn and adult rats. In addition, a quantitative analysis of DBH- and PNMT-immunoreactive fibers in the medial parvocellular subnucleus, dorsal division (PVNmpd) and posterior magnocellular subnucleus, lateral division (PVNpml) was performed in adult rats and in developing rats on postnatal day (P)1, P7, P14, and P21. The numbers of PVN-projecting neurons in the A1, C1, A2/C2, C3, or A6 catecholamine cell groups were similar in newborn and adult rats, as were the proportions of PVN-projecting neurons in each region that were PNMT-positive. However, fewer PVN-projecting neurons in the C1 and C3 regions expressed DBH immunolabeling in newborn rats compared to adults. DBH immunolabeling increased progressively in the PVNmpd and PVNpml between postnatal days P1 and P21, when adult-like levels were achieved. Conversely, PNMT immunolabeling in the same PVN subdivisions was most dense at P1, gradually decreasing to adult-like levels by P21. These dynamic developmental changes in catecholamine synthetic enzyme immunolabeling densities in the PVN may reflect functional changes in noradrenergic and adrenergic signaling capacity in rats during the first few weeks of postnatal development.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Axonal Transport
- Axons
- Brain Stem
- Catecholamines
- Cell Count
- Cholera Toxin
- Dopamine beta-Hydroxylase
- Female
- Fluorescent Dyes
- Hypothalamo-Hypophyseal System
- Immunohistochemistry
- Male
- Neural Pathways
- Neurosecretion
- Neurosecretory Systems
- Paraventricular Hypothalamic Nucleus
- Phenylethanolamine N-Methyltransferase
- Rats
- Rats, Sprague-Dawley
Pheochromocytomas in mice are rare tumors, and their expression of functional markers has not previously been assessed. In this study, 29 spontaneously occurring mouse pheochromocytomas were characterized morphologically and immunohistochemically to determine whether there are functional correlates to previously described morphological features and to provide a database for comparison with tumors that arise in genetically engineered animals. The tumors were derived from 28 mice 828-1,489 days old, of three genotypes. Considerable cytological and architectural polymorphism was observed both within and between tumors. Most of the tumor cells were comparable in size to normal chromaffin cells or were larger. Small basophilic cells, which are the predominant cell type in rat pheochromocytomas, were usually in the minority. All of the tumors and most of the cells within individual tumors expressed immunoreactive tyrosine hydroxylase (TH). The tumors were variably positive for phenylethanolamine-N-methyltransferase (PNMT) and chromogranin A (CGA). There did not appear to be a global association of specific cytological features with expression of TH, PNMT, or CGA, although cells of similar appearance often shared similar immunoreactivities within individual tumors. Small basophilic cells could be either PNMT-positive or PNMT-negative. The frequency, morphology, and immunophenotype of mouse pheochromocytomas suggest that the mouse may be more appropriate than the rat as a model for human adrenal medullary pathology. In addition, the expression of immunoreactive PNMT by mouse pheochromocytomas suggests that these tumors are a potential source of epinephrine-producing cell lines, for which adequate models currently do not exist.
MeSH Terms
- Adrenal Gland Neoplasms
- Aging
- Animals
- Female
- Immunohistochemistry
- Male
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Pheochromocytoma
- Rodent Diseases
We examined whether or not the number of noradrenergic and adrenergic neurons changes with age, using peroxidase antiperoxidase (PAP) immunohistochemistry with specific antisera against tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT). TH- and PNMT-immunoreactive neurons were counted in every noradrenergic and adrenergic neuron group of young (3-month-old) and old (24-month-old) rats. The differences in the counted number of TH- and PNMT-immunoreactive neurons did not reach statistical significance between the young and old rats.
MeSH Terms
- Aging
- Animals
- Brain Stem
- Cell Count
- Epinephrine
- Immunoenzyme Techniques
- Male
- Neurons
- Norepinephrine
- Phenylethanolamine N-Methyltransferase
- Rats
- Rats, Sprague-Dawley
- Tyrosine 3-Monooxygenase
The 'growth-associated protein', GAP-43 was originally considered to be a neuron-specific protein associated with plasticity. However, we have recently shown that GAP-43 is expressed by noradrenergic, but not by adrenergic chromaffin cells in the adult rat adrenal gland. In this study, we examine the expression of GAP-43 during embryonic and post-natal development of the adrenal gland using immunohistochemical techniques. In parallel, antibodies directed against two neuroendocrine markers, the catecholamine-synthesizing enzymes, tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) were employed to permit identification of the developing chromaffin cell phenotypes. At embryonic day 15.5, GAP-43 was predominately localized in sympathoadrenergic precursor cells in the extra-adrenal blastema, and also in nerve fibers within the adrenal gland. At later embryonic stages, GAP-43 was expressed by nearly all intra-adrenal chromoblasts. Two subsets of chromoblasts can be distinguished even at early stages. A strong GAP-43-positive immunoreaction was observed in those chromoblasts organized in a few large compact clusters which weakly expressed TH and did not express PNMT. A generally weaker GAP-43 immunoreaction was observed in a second type of intra-adrenal chromoblasts which were organized in small isolated groups and characterized by a PNMT-positive, and strong TH-positive immunoreactivity. GAP-43 immunoreactivity was still associated with many PNMT-positive adrenergic chromoblasts at birth, but decreased to undetectable levels during the first post-natal week. By the second post-natal week, GAP-43 was restricted, as in the adult, to noradrenergic chromaffin cells which expressed TH, but not PNMT, in addition to nerve fibers and their associated glial cells in the gland. An immunoblot analysis confirmed a decrease in GAP-43 protein during the post-natal period. In agreement with these observations, a three-fold decrease in GAP-43 mRNA in the adrenal gland was measured between late embryogenesis and the second post-natal week. During development, the spatiotemporal expression of GAP-43 suggests a possible role in the migration and aggregation of chromaffin cell precursors into the medullary region of the adrenal gland.
MeSH Terms
- Adrenal Glands
- Aging
- Animals
- Blotting, Western
- DNA Primers
- Embryo, Mammalian
- Embryonic and Fetal Development
- Fluorescent Antibody Technique
- GAP-43 Protein
- Gene Expression
- Gestational Age
- Growth Substances
- Immunohistochemistry
- Membrane Glycoproteins
- Nerve Tissue Proteins
- Phenylethanolamine N-Methyltransferase
- Polymerase Chain Reaction
- RNA, Messenger
- Rats
- Rats, Wistar
- Tyrosine 3-Monooxygenase
The changes of phenylethanolamine-N-methyltransferase (PNMT, EC 2.1.1.28), the enzyme that catalyzes the final step in the biosynthesis of adrenaline, were studied during the development of several regions of rat brain. PNMT is present in medulla oblongata-pons, hypothalamus, cerebellum, and midbrain five days before birth, and a progressive increase in the enzyme activity is observed during development. The adult levels are attained between 15 and 20 days, depending on the region. The increases in PNMT activity in the rostral regions are higher than in the caudal regions. PNMT attains adult levels earlier than tyrosine hydroxylase and dopamine-beta-hydroxylase. The apparatus for adrenaline synthesis seems to be mature at three weeks after birth in the medulla oblongata-pons, which contains the cell bodies of adrenaline-containing neurons. In the other regions the adult levels of enzyme activity are attained at 15 days after birth.
MeSH Terms
- Aging
- Animals
- Brain
- Cerebellum
- Female
- Hypothalamus
- Medulla Oblongata
- Mesencephalon
- Phenylethanolamine N-Methyltransferase
- Pons
- Pregnancy
- Rats
We have studied the uptake mechanism, biochemistry and autoradiographic localization of a descending epinephrine-containing pathway in the chick spinal cord. This epinephrine (E) projection has a developmental timetable (appears at 14 days in ovo) that is different from those of the serotonin (5-HT) and norepinephrine (NE) projections which appear at 8 and 12 days respectively. E possesses its own uptake mechanism with different pharmacological specificities from those of the NE and 5-HT uptake mechanisms. Phenylethanolamine-N-methyltransferase (PNMT), the enzyme that converts NE to E, is present in the cord at 14 days in ovo which is the same time that the uptake mechanism is detectable. Transection of the spinal cord at upper thoracic levels almost completely eliminates the uptake mechanism and PNMT activity below the transection, indicating a supraspinal origin of this pathway. E can first be detected fluorimetrically at 12 days in ovo but at this age E appears not to be of supraspinal origin since transmission at 5 days in ovo does not deplete the spinal cord of E. However, transection of the spinal cord at 3 days post-hatching does markedly reduce the E content by 12 days. Autoradiographic analysis after uptake with [3H]E shows a circumscribed localization of the uptake of E to the neuropil of the preganglionic sympathetic nucleus (nucleus of Terni). These observations demonstrate the presence of a separate descending epinephrine-containing projection in the avian spinal cord which terminates predominantly on preganglionic sympathetic neurons. This pathway may be the major central autonomic pathway in the avian spinal cord.
MeSH Terms
- Aging
- Animals
- Autoradiography
- Biological Transport
- Chick Embryo
- Chickens
- Epinephrine
- Phenylethanolamine N-Methyltransferase
- Spinal Cord
- Tritium
The enzymatic activities of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) were determined in adrenals of spontaneously hypertensive rats (SHR) and controls of the Wistar-Kyoto-strain (WKY) of different ages. In SHR of all examined age groups (10, 14 and 26 weeks) lower enzyme activities were found than in WKY rats of the same ages. That was more evident for PNMT than for DBH, SHR show a clear asymmetric distribution or PNMT with higher values in the left adrenals. This concerns 10, 14 and 26-week-old animals. An asymmetric distribution of DBH with higher values in the right adrenals were shown only in 14 and 26 weeks old rats. The asymmetric distribution was generally more obvious in SHR. This fact could be related to changes in the control of the connections between hypophysis and adrenals during development of hypertension.
MeSH Terms
- Adrenal Glands
- Aging
- Animals
- Blood Pressure
- Dopamine beta-Hydroxylase
- Hypertension
- Male
- Phenylethanolamine N-Methyltransferase
- Rats
- Rats, Inbred Strains
Epinephrine (E) and phenylethanolamine N-methyltransferase (PNMT) are endogenous to the rat retina. The retinal enzyme shows substrate specificity and inhibitor sensitivity similar to the PNMT of brain. The E system in the retina may be part of a functional adrenergic system, because amine metabolism of dopamine-containing amacrine cells is inhibited by alpha 2 agonists and stimulated by alpha 2 antagonists.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Dexamethasone
- Dopamine
- Epinephrine
- Kinetics
- Norepinephrine
- Phenylethanolamine N-Methyltransferase
- Rats
- Retina
- Substrate Specificity
The pre- and postnatal development of the adrenal medulla was examined in the rat by immunohistochemistry and by assay of catecholamines. Immunohistochemistry involved the use of antibodies to noradrenaline (NA), adrenaline (A) and the biosynthesizing enzymes dopamine beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT). Adrenal glands were obtained from animals from the 16th day of gestation to the 7th postnatal day at daily intervals, and at the 14th postnatal day, and from adult rats. Tissues were fixed in ice-cold, 4% paraformaldehyde, buffered at pH 7.3. Cryostat sections (7 microns) were stained with the indirect immunofluorescence technique. Adrenals from the same developmental stages were assayed for the presence of DA (dopamine), NA and A by ion-pair reversed-phase liquid chromatography with electrochemical detection. In adult adrenals the majority of the medullary cells (approximately 80%) were highly immunoreactive to A and moderately immunoreactive to NA. They also showed immunoreactivity to both DBH and PNMT, i.e., they are synthesizing and storing A. The remaining cell clusters were only stained by antibodies to DBH and NA (NA-synthesizing and -storing cells). These findings correlate well with the relative concentrations of A and NA as determined by assay. Three developmental phases could be distinguished. In the first phase, the 16th and 17th prenatal day, medullary cells were only immunoreactive to DBH and NA, and only very small amounts of A as compared to NA were found. During the second period, from the 18th prenatal day to 2 or 3 days after birth, all medullary cells were immunoreactive to DBH, NA, PNMT and A, and during this phase the adrenaline concentration increased daily and became the predominant amine on the 20th day of gestation. Adrenaline represented 75% of total catecholamine on the 1st to 3rd day after birth. The third phase started at the 2nd or 3rd postnatal day and was characterized by the presence of an increasing number of medullary cells solely immunoreactive to DBH and NA, hence synthesizing and storing NA. The remaining cells were immunoreactive to DBH, NA, PNMT and A. Postnatally, the relative concentration of A continued to rise reaching 79% by the 4th postnatal day. These results indicate that initially the adrenal medullary cells are synthesizing and storing almost exclusively NA.(ABSTRACT TRUNCATED AT 400 WORDS)
MeSH Terms
- Adrenal Medulla
- Aging
- Animals
- Chromaffin System
- Dopamine beta-Hydroxylase
- Epinephrine
- Fluorescent Antibody Technique
- Gestational Age
- Histocytochemistry
- Norepinephrine
- Phenylethanolamine N-Methyltransferase
- Rats
- Rats, Inbred Strains
To study the differentiation of adrenergic (epinephrine-synthesizing) neurons in brain, the initial appearance and ontogeny of phenylethanolamine N-methyltransferase (PNMT), a specific marker of the adrenergic phenotype, were studied with immunocytochemistry and catalytic assay. The appearance of immunoreactivity to dopamine beta-hydroxylase (DBH-IR), an enzyme common to the noradrenergic and adrenergic phenotypes, was also studied. DBH-IR was initially observed on embryonic Day 13 (E13) in cells located on the ventrolateral floor and wall of the rhombencephalon. A day later (E14), PNMT-IR cells and PNMT catalytic activity were observed in the rhombencephalon suggesting that, as in the adrenal gland, noradrenergic expression precedes adrenergic expression. The PNMT-IR cells were presumed to be precursors of C1 neurons since they were located in the ventrolateral medulla oblongata. Cells located in the wall of the medulla which appeared to be migrating ventrally to the C1 group also contained PNMT-IR. On E15, cells which had PNMT-IR processes coursing through the germinal zone were observed dorsally near the fourth ventricle. Although the location of the C1 cell group was apparent when PNMT was initially expressed, the dorsal C2 and C3 adrenergic cell groups were not evident until late in gestation on E19. Even in the term embryo there appeared to be PNMT-IR cells which had not yet reached their final destination. On E14 and E15, PNMT-IR cells were also observed on the floor of the pons just rostral to the pontine flexure. However, these were not observed in older embryos, suggesting that transient expression of PNMT occurs in brain, as well as in the periphery. To determine whether glucocorticoids regulate brain PNMT, we examined the effects of altered glucocorticoid levels. In contrast to PNMT in the sympathetic nervous system, PNMT activity in medulla oblongata was not affected in neonates or adults by the decrease in glucocorticoids following adrenalectomy or hypophysectomy. Conversely, elevation of glucocorticoids by hormonal treatment did not alter PNMT in neonates. Notably, however, treatment of pregnant rats with dexamethasone on E18-E21, but not earlier, increased PNMT activity in the fetal brain stem. These observations suggest that PNMT expression and development is regulated by different factors in cells derived from neural crest and tube. PNMT is expressed earlier in brain than in adrenal and sympathetic ganglia. Further, the development of PNMT in the periphery, but not in the brain, is dependent on maintenance of physiological levels of glucocorticoids.(ABSTRACT TRUNCATED AT 400 WORDS)
MeSH Terms
- Adrenalectomy
- Aging
- Animals
- Brain Stem
- Corticosterone
- Dexamethasone
- Female
- Fluorescent Antibody Technique
- Ganglia, Sympathetic
- Glucocorticoids
- Hydrocortisone
- Medulla Oblongata
- Phenylethanolamine N-Methyltransferase
- Pregnancy
- Rats
The postnatal evolution of adrenal phenylethanolamine-N-methyltransferase (PNMT) activity is slightly accelerated by hypothyroidism and slowed by hyperthyroidism. In 14-day-old rats a single stimulation of the adrenals by insulin-induced hypoglycemia does not lead to any change in enzymatic activity. If the stimulation is repeated for 4 days, it leads to a net increase in adrenal PNMT activity in the control rats, while no increase occurs in hypo- or hyperthyroid animals.
MeSH Terms
- Adrenal Glands
- Aging
- Animals
- Animals, Newborn
- Female
- Insulin
- Male
- Phenylethanolamine N-Methyltransferase
- Rats
- Thyroid Hormones
A computer-assisted morphometrical and microdensitometrical analysis has been performed on cardiovascular noradrenaline (NA), adrenaline (A) and neuropeptide (Y (NPY) neurons in adult and 24-month-old male rats and on hypotensive (LL), normotensive (LN) and hypertensive (LH) male rats of the Lyon strain using the indirect immunoperoxidase procedures. It was found that in NPY/phenylethanolamine-N-methyltransferase (PNMT) costoring neurons of the CI area of the rostral medulla oblongata NPY-like immunoreactivity showed a more marked reduction than the PNMT immunoreactivity. Furthermore, within the parvocellular part of the paraventricular hypothalamic nucleus. NPY immunoreactive nerve terminal profiles were much more affected than the PNMT immunoreactive profiles during aging as revealed by a marked reduction in the number of profiles and by a marked reduction of absorbency values in the microdensitometrical analysis. Thus, in the NPY/PNMT costoring neurons of the A C1 group of the ventrolateral medulla projecting, for example, to the hypothalamus, the peptide transmission line may have a special vulnerability to the aging processes which may contribute to the development of hypertension in old people in view of a vasodepressor role of many central NPY/PNMT neurons. An extensive morphometrical and microdensitometrical analysis of the various catecholamine (CA) cell groups of the medulla oblongata of the LL, LN and LH rats of the Lyon strain was performed. In a comparison between LL and LH rats the A2 cell group of the LH strain showed a trend for an increase in the mean tyrosine hydroxylase (TH) immunoreactive cell body area and the C3 group showed a significant increase in the number of PNMT immunoreactive profiles.(ABSTRACT TRUNCATED AT 250 WORDS)
MeSH Terms
- Aging
- Animals
- Catecholamines
- Densitometry
- Hypertension
- Immunoenzyme Techniques
- Male
- Medulla Oblongata
- Neurons
- Neuropeptide Y
- Phenylethanolamine N-Methyltransferase
- Rats
- Rats, Inbred Strains
To examine the possible existence of changes in the adrenal catecholaminergic activity during aging, we analyzed the adrenal content of catecholamines (CA) and the activities of selected enzymes involved in their metabolism as well as the basal and the K -stimulated release of these CA in incubated adrenal tissue of aged (greater than 22 months) and young (2 months) rats of both sexes. Adrenal contents of norepinephrine (NE) and epinephrine (E) of male rats were unaltered in aging, although aged males showed an increased activity of tyrosine hydroxylase (TH) and a decrease in phenylethanolamine-N-methyl transferase (PNMT) activity. In addition, the in vitro release of both CA as well as their content in the incubated adrenal tissue were higher in aged males than in young animals. However, the response of the adrenal of aged males to incubation with stimulatory concentrations of K was significantly lower than that observed in young males. Aged females showed increases in the adrenal content of E, although the activities of TH and PNMT were unaltered. As in aged males, the in vitro release of CA from incubated adrenal tissue was higher in aged females than in young rats, but the CA amounts measured in the incubated tissues were similar. Moreover, the response to stimulatory concentrations of K was lower in aged females than in young animals. In summary, these results clearly indicate that adrenal catecholaminergic activity is enhanced during aging, which could have important consequences for physiological functions regulated by the adrenal secretion. Also, some differences in the effects of aging could be observed between males and females.
MeSH Terms
- Adrenal Glands
- Age Factors
- Aging
- Animals
- Catecholamines
- Female
- Male
- Rats
- Rats, Inbred Strains
- Sex Factors
Phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) has been used as a marker to examine development of adrenergic expression in the rat adrenal gland and the putative role of glucocorticoids in this process. PNMT enzymatic activity increases 7-10-fold from birth to postnatal day 35. Immunotitration studies show that PNMT protein only increases 4-5-fold during this same time period. Moreover, the slopes from the immunotitration curves decrease with increasing age. Thus, a more active enzyme with lower affinity for the antiserum appears to be present in the older animals. Quantitative solution hybridization shows that PNMT mRNA increases 2.5-fold from birth through postnatal day 11. Thereafter, it declines, and eventually plateaus at values insignificantly different from birth by postnatal day 25. Northern analysis further shows that two forms of PNMT mRNA are expressed. Adrenal corticosterone remains low from birth through postnatal day 11, but then increases nearly 10-fold by adulthood. The lack of concordance between changes in PNMT activity, protein, and mRNA suggests that adrenergic expression is developmentally regulated at multiple levels; the above provides evidence for both transcriptional and post-transcriptional controls, since changes in PNMT mRNA may differ in both magnitude and direction from changes in PNMT activity and protein during the developmental window examined. These developmental regulatory mechanisms may be in part glucocortocoid-mediated, but corticosteroid control of PNMT gene expression does not appear to be the predominant mechanism of control.
MeSH Terms
- Actins
- Adrenal Glands
- Aging
- Animals
- Animals, Newborn
- Blotting, Northern
- Corticosterone
- DNA Probes
- Phenylethanolamine N-Methyltransferase
- RNA
- RNA Probes
- Rats
- Rats, Inbred Strains
Given the importance of the swine (Sus scrofa) as an animal model for human development, physiology and disease, neurons containing the epinephrine-synthesizing enzyme, phenylethanolamine N-methyltransferase (PNMT), were mapped in the medulla oblongata of neonatal swine as a first step in identifying their roles in central autonomic control. Neurons were labeled immunocytochemically by using an antiserum to PNMT raised in rabbits against trypsin-treated enzyme purified from the bovine adrenal gland. The general regional organization of neurons expressing PNMT (-like) immunoreactivity (ir) in the neonatal swine was similar to data obtained in other species and, in some aspects, more closely resembled the pattern observed in the primate brain. Immunolabeled cells appeared to be more abundant and caudally more extensive than observed in other adult animals. PNMT-immunoreactive (ir) neuronal somata, however, were largely confined to the reticular formation in the ventrolateral quadrant and the nucleus tractus solitarii (NTS) and more restricted in distribution than those expressing tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (D beta H)-ir on serial transverse sections. A close correspondence was observed between the distributions of TH- and PNMT-ir neurons and processes throughout the C1 and C2 areas. However, in the C1 and C3 regions TH-ir neurons outnumbered those containing D beta H and PNMT-ir. In contrast, cell groups enriched in PNMT-ir neurons and processes were characterized by relatively weak D beta H-ir. In the ventrolateral medulla (VLM), PNMT-ir cell bodies were concentrated rostrally and extended from the caudal pole of the facial nucleus to a level posterior to the calamus scriptorius. The rostral VLM was characterized by an admixture of bipolar and multipolar primarily medium-diameter immunostained neurons. A prominent cell column (condensation) organized ventromedially to the nucleus ambiguus pars compactus (NAc). A loosely organized cluster bordered the lateral aspect of the special visceral efferent column; another smaller aggregate was located in the ventromedial reticular formation adjacent to the inferior olive. At middle medullary levels, PNMT-ir neurons formed two distinct subgroups (dorsal and ventral) interrupted by a band of precerebellar relay neurons that extended between the medial and lateral limbs of the lateral reticular nucleus of Walberg. At obex, the dorsal cell group formed a diagonal array and assumed a position dorsal and dorsolateral to the medial limb of LRN. This group was distinguished by bipolar neurons with axes of orientation directed perpendicularly to the majority of neurons in the rostal VLM or those lying near the caudal ventromedullary surface.(ABSTRACT TRUNCATED AT 400 WORDS)
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Dopamine beta-Hydroxylase
- Epinephrine
- Immunohistochemistry
- Medulla Oblongata
- Neurons
- Phenylethanolamine N-Methyltransferase
- Swine
- Tyrosine 3-Monooxygenase
Cell adhesion molecules play a major role in determining tissue architecture during histogenesis. This immunocytochemical study of the adrenal gland examines the embryonic and early postnatal cellular expression of two neural cell adhesion molecules, NCAM and L1, which are widely expressed in brain and have been found also to be expressed in the adult rat adrenal gland. In parallel, antibodies directed against two neuroendocrine cell markers, tyrosine hydroxylase and phenylethanolamine N-methyltransferase, were employed to verify the phenotypic nature of developing chromaffin cells in order to correlate cell adhesion molecule expression with the state of chromaffin cell differentiation. NCAM was found to be expressed by chromoblasts within extra-adrenal blastema (i.e. before their migration into the cortical primordium) at the 16th day of embryonic life. It continued to be expressed by all developing chromaffin cells after their infiltration into the developing adrenal gland at all ages. L1 was also expressed by chromoblasts in extra-adrenal sites, but was found only in a subpopulation of chromaffin cells within the cortical primordium from the 16th embryonic day onwards. Those chromoblasts which expressed L1 constituted relatively large compact cell clusters within the gland at this stage, while intra-adrenal chromaffin cells not expressing L1 were dispersed in small cell groups. L1 was also strongly expressed by nerve fibres (and their surrounding Schwann cells) which appeared to innervate cell groups as early as the 16th embryonic day. Both extra- and intra-adrenal chromoblasts expressed tyrosine hydroxylase, but the large L1-positive cell aggregates were less intensely immunoreactive for tyrosine hydroxylase than were cells in small groups. PNMT expression was restricted to L1-negative intra-adrenal chromoblasts present in small groups. Ultrastructural observations demonstrated that cells expressing L1 contained few secretory granules at the 18th embryonic day. It is concluded from these data that these chromoblasts are the precursors of the noradrenergic cells found in the mature gland. In addition, the arrangement of noradrenergic chromaffin cells in the form of homotypic cell groups throughout the course of histogenesis of the adrenal medulla is likely to be a direct consequence of the exclusive co-expression of both NCAM and L1 by this subpopulation of maturing chromaffin cells.
MeSH Terms
- Adrenal Glands
- Aging
- Animals
- Cell Adhesion Molecules
- Cell Adhesion Molecules, Neuronal
- Fluorescent Antibody Technique
- Gestational Age
- Microscopy, Immunoelectron
- Models, Biological
- Phenylethanolamine N-Methyltransferase
- Rats
- Tyrosine 3-Monooxygenase
Activities of monoamine oxidase (MAO), DOPA-decarboxylase (DD), phenoletha-nolamine-N-methyltransferase (PNMT) and phosphodiesterase (PDE) were studied in the brain and its parts, heart, kidneys, adrenals and liver in developing rats. In vitro, the action of nialamid on MAO activity in the liver, RO-4-4602 on DD activity in the liver, and D(-) INPEA on PNMT activity in the adrenals was investigated. The influence of 6-hydroxydopamine (6-OHDA), 200 mg/kg i. p., on MAO activity in the liver of developing rats was also studied. Irregular changes in activities of examined enzymes during development were observed. 6-OHDA, nialamid and RO-4-4602 inhibited enzyme activities in young rats more strongly than in adult animals.
MeSH Terms
- Adrenal Glands
- Age Factors
- Aging
- Animals
- Animals, Newborn
- Benserazide
- Brain
- Catecholamines
- Dopa Decarboxylase
- Enzyme Inhibitors
- Ethanolamines
- Hydroxydopamines
- Kidney
- Liver
- Male
- Methyltransferases
- Monoamine Oxidase
- Myocardium
- Nialamide
- Phenols
- Phosphoric Diester Hydrolases
- Rats