Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of estradiol-17 alpha to serve as a substrate for estrogen-2/4-hydroxylase in rabbit hypothalamic tissue was determined and compared to that of estradiol-17 beta. Both 2- and 4-hydroxy metabolites of estradiol-17 alpha were formed by the hypothalamic tissue in vitro. The rates of formation of 2-hydroxyestradiol (2-OHE2)-17 alpha and -17 beta were similar as were their kinetic constants (Km and Vmax). In addition, 2-OHE2-17 alpha was shown to inhibit purified rat adrenal tyrosine hydroxylase with a potency comparable to that of 2-OHE2-17 beta, a finding similar to that reported by others with respect to catechol-o-methyltransferase. Since estradiol-17 alpha has a markedly reduced affinity for estrogen receptors compared with extradiol-17 beta, this steroid could be useful in studies designed to distinguish between receptor mediated effects of estrogens and effects that locally formed catechol estrogens may have through their direct interaction with catecholaminergic system in neural tissue.
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PMID:The catechol estrogen, 2-hydroxyestradiol-17 alpha, is formed from estradiol-17 alpha by hypothalamic tissue in vitro and inhibits tyrosine hydroxylase. 612 6

The localization of catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT)], of serotonin (5-HT), and adrenocorticotropin (ACTH) in the pituitary of bullfrog (Rana catesbeiana), rat, hamster, and dog was examined by the immunofluorescence method. Many TH- and DBH-positive but PNMT-negative noradrenalin cells and 5-HT-positive serotonin cells were first observed in the pars distalis of the frog pituitary together with small numbers of ACTH-positive cells, in marked contrast to our previous findings that TH-positive but DBH-negative dopamine cells are rare in the anterior lobe of rat and dog pituitary. The entire population of cells of the pars intermedia showed a weak ACTH-like immunoreaction. Although most of these cells were TH- or 5-HT-negative, TH-positive but DBH-negative dopaminergic varicose fibers surrounded these cells. Among cells of the pars intermedia of the frog, 5-HT-positive cells with processes were also scattered. In the neural lobe, TH- and 5-HT-immunoreactive fibers were rarely seen.
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PMID:Existence of noradrenalin cells and serotonin cells in the pituitary gland of Rana catesbeiana. 613 Aug 47

Recent data have shown that 5 days after intraventricular injection of 6-hydroxydopamine (6-OHDA), the tyrosine hydroxylase activity (TH) was increased within the locus coeruleus (LC). We sought to determine if such an alteration occurs within the A1 and A2 noradrenergic (NA) and C1 and C2 adrenergic (A) neurons of the rat medulla oblongata. The TH activity within the cell bodies was significantly increased 2 days after 6-OHDA injection with a maximum at 5 days (LC, + 109%, P less than 0.001; A1-C1, + 40%, P less than 0.01; A2-C2; + 24%, P less than 0.01) while a significant decrease was present 21 days after 6-OHDA. Conversely, dopamine-beta-hydroxylase (DBH) activity exhibited a decrease which was maximal at 21 days (LC,-41%; A1-C1,-33%; A2-C2,-35%, P less than 0.001). Both the TH (-47% at 5 days) and the DBH (-82% at 12 days) activities were decreased within the terminals of the tractus intermediolateralis (TIML). The phenylethanolamine-N-methyltransferase (PNMT) activity was never altered in the cell bodies nor in the terminals analyzed. These data demonstrate that the NA neurons of the rat medulla oblongata and of the LC exhibit a similar pattern of response to the neurotoxin 6-OHDA. Conversely, the lack of change in the PNMT activity confirms the hypothesis of a resistance of the A neurons to 6-OHDA or questions the validity of the PNMT as an A marker.
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PMID:Time course study of changes in the activity of the catecholamine synthesizing enzymes in the rat medulla oblongata after intraventricular injection of 6-hydroxydopamine. 613 62

By using preferential microdissection of the adrenaline (A) and noradrenaline (NA) neurons within the A2-C2 region of the rat medulla oblongata, it was possible to study the biochemical response of these two neuronal populations to reserpine administration. Three days after reserpine injections (10 mg/kg s.c., per day for 3 days), tyrosine hydroxylase (TH) activity was increased in the adrenergic C2 region whilst no change was observed in the noradrenergic A2 region. The response of the A neurons to reserpine was of lesser magnitude than the increase in TH activity observed under the same conditions in the NA neurons of the locus coeruleus and of the A5 region, and was likely to have originated in the A cell bodies. In contrast with previous studies, this work suggests that the A-containing neurons are responsive to reserpine administration, despite the lack of change in phenylethanolamine-N-methyltransferase activity.
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PMID:Increased tyrosine hydroxylase activity in central adrenaline neurons after reserpine treatment. 613 64

The distribution of catecholamine neurons in the dorsal vagal complex is described on the basis of indirect immunofluorescence histochemistry using antisera to three enzymes in the catecholamine synthesis, tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase, allowing differentiation between dopamine, noradrenaline and adrenaline cells. In addition attention was focused on the occurrence of two peptides, neuropeptide Y (NPY) and neurotensin in this region. It could be established that they partly were present in subpopulations of the A2/C2 catecholamine neurons. The significance of this coexistence of a peptide and a catecholamine is discussed.
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PMID:Transmitter and peptide systems in areas involved in the control of blood pressure. 614 54

The immunocytochemical localization of the biosynthetic enzymes--tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT)--was used to determine the cytological features and precise neuroanatomical location of catecholaminergic neurons in the medulla oblongata of rat. Perikarya labeled with TH were detected in two bilaterally symmetrical columns located in the ventrolateral and dorsomedial medulla. The distribution and the number of neuronal perikarya containing TH were the same as those containing DBH, except in the dorsal motor nucleus of the vagus at the level of the area postrema where the number of neurons immunocytochemically labeled for TH was considerably greater than those labeled for DBH. The detection of perikarya which show immunoreactivity for TH, used in the biosynthesis of dopamine, noradrenaline, and adrenaline, but not DBH, which converts dopamine to noradrenaline, suggests the existence of dopamine-synthesizing neurons in the medulla. Perikarya labeled with PNMT, used in the biosynthesis of adrenaline, were localized in more restricted regions corresponding to rostral subsets of the dorsal and ventral groups labeled for TH and DBH. Counts of neurons immunocytochemically labeled for TH or PNMT were obtained in order to determine the relative ratio of neurons which contain the enzymes necessary for the synthesis of dopamine, noradrenaline, or adrenaline at various levels of the medulla. At the most caudal levels no PNMT labeled neurons were detected. Further rostral, PNMT-labeled neurons were first detected in the ventrolateral medulla. At the level of the area postrema, the number of PNMT-labeled neurons in the ventrolateral medulla was approximately half of the number of cells showing immunoreactivity for TH. In contrast, few PNMT-labeled cells were detected in the dorsomedial medulla at the level of the area postrema compared to many neurons labeled for TH. At rostral medullary levels, in both the ventrolateral and the dorsomedial regions, the number of neurons labeled for TH and PNMT was essentially the same. Thus most, if not all, of the catecholaminergic neurons in the rostral medulla have PNMT, necessary for the synthesis of adrenaline.
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PMID:Distribution of dopamine-, noradrenaline-, and adrenaline-containing cell bodies in the rat medulla oblongata: demonstrated by the immunocytochemical localization of catecholamine biosynthetic enzymes. 614 61

Regulation of the putative peptide neurohumour [Leu]enkephalin and the catecholaminergic enzymes tyrosine hydroxylase and phenylethanolamine-N-methyl-transferase was examined in the rat adrenal medulla in vivo and in vitro. Surgical denervation of the adrenal gland or pharmacologic blockade of synaptic transmission, treatments known to decrease catecholamine traits, increased [Leu]enkephalin content. Medullas explanted to culture exhibited a 50-fold rise in [Leu]enkephalin in 4 days, whereas tyrosine hydroxylase remained constant, and phenylethanolamine-N-methyltransferase decreased to a new baseline level. Veratridine-induced depolarization prevented the accumulation of [Leu]enkephalin, an effect that was blocked by tetrodotoxin, which antagonizes transmembrane Na+ influx. These studies suggest that enkephalinergic and catecholamine characters are differentially regulated by impulse activity and depolarization in the adrenal medulla.
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PMID:Impulse activity differentially regulates [Leu]enkephalin and catecholamine characters in the adrenal medulla. 614 83

By using a new microdissection procedure allowing the noradrenaline (NA) and adrenaline (A) cell groups of the A2-C2 region to be sampled preferentially, it was possible to study the biochemical response of these two neuronal populations after 6-hydroxydopamine (6-OHDA) administration. Five days after an intraventricular 6-OHDA injection, tyrosine hydroxylase (TH) activity increased (+104%, P less than 0.01) in the adrenergic C2 region, in the locus coeruleus (LC) and in the A1-C1 region, while the NA A2 region exhibited no significant increase. Twenty-one days after 6-OHDA administration, dopamine-beta-hydroxylase (DBH) activity had decreased in both the noradrenergic regions (LC, A1-C1 and A2 regions) and in the C2 adrenergic region. Conversely, phenylethanolamine-N-methyltransferase (PNMT) activity was not modified either in the cell bodies or in the terminals located in the tractus intermediolateralis of the spinal cord and in the hypothalamic nuclei. These data suggest: (i) that adrenaline-containing neurons could be sensitive to the neurotoxic action of 6-OHDA since they exhibit changes in TH and DBH activities; and (ii) that the determination of PNMT activity may not be sensitive enough to estimate the functional integrity of the A cell bodies or terminals.
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PMID:Changes in tyrosine hydroxylase and dopamine-beta-hydroxylase activities but not in phenylethanolamine-N-methyltransferase activity within central adrenaline neurons after 6-hydroxydopamine administration. 614 23

Primary cultures of bovine adrenal chromaffin cells provide large quantities of a homogeneous population of target cells for nerve growth factor (NGF) and, thus, are a suitable system for studying the molecular mechanism of action of NGF. In this study, we have shown that NGF mediates the specific induction of the key enzymes in catecholamine biosynthesis, tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT). Acetylcholinesterase (AChE), an enzyme which catalyzes the breakdown of acetylcholine, is also induced by NGF. We have compared NGF-mediated TH and AChE induction and have provided pharmacological evidence that TH induction involves a post-transcriptional, polyadenylation-dependent event (blockable by 9-beta-arabinofuranosyladenine but not by alpha-amanitin), whereas AChE induction requires transcription (blockable by alpha-amanitin). DBH and PNMT appear to be regulated via the same mechanism as TH. The time course of TH induction is such that NGF must be continuously present for at least the first 36 hr (during which time TH levels remain unchanged), and then the entire increase takes place during the subsequent 12 hr. In contrast, AChE induction proceeds linearly with time of NGF exposure. These data suggest that there may be multiple mechanisms by which NGF regulates enzyme induction. We have also compared the effects of cAMP with those of NGF. As compared to NGF, cAMP produces a different pattern of enzyme induction (in addition to TH, DBH, PNMT, and AChE, dopa decarboxylase (DDC) is also induced), it acts rapidly (a 12-hr exposure produces the full effect), and it acts only at the transcriptional level (its effects are blocked by alpha-amanitin). These data provide evidence that cAMP does not act as a second messenger for NGF with regard to enzyme induction.
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PMID:Nerve growth factor-mediated enzyme induction in primary cultures of bovine adrenal chromaffin cells: specificity and level of regulation. 614 60

The catecholamine-synthesizing enzymes, tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase were examined by immunohistochemistry in hypertrophied paraganglia of aged male Fischer-344 rats. All paraganglionic cells reacted with antibodies against tyrosine hydroxylase. Dopamine beta-hydroxylase was identified in most paraganglionic cells, indicating that they synthesized norepinephrine. A variable number of paraganglia were positive for phenylethanolamine-N-methyltransferase, which suggested that they synthesized epinephrine. The formaldehyde-induced fluorescence method demonstrated greenish-yellow fluorescence or yellowish-brown fluorescence. The intensity of the fluorescence was in the same range as in adrenal medullary cells. The observations indicate that paraganglia are capable of synthesizing epinephrine.
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PMID:Catecholamine-synthesizing enzymes in paraganglia of aged Fischer-344 rats. Immunohistochemistry and fluorescence microscopy. 615 Jul 62


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