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

Previous work from our laboratory has indicated that ovine prolactin can produce a rapid stimulation (within 1 h) of dopamine release from nigrostriatal and mesolimbic dopaminergic neurons of male rats. In the present experiment we attempted to determine whether this effect of prolactin was a function of an increase in the activation of dopamine synthesis. To examine this possibility we used the drug NSD 1015. This drug is a decarboxylase inhibitor that leads to dopa accumulation and is used as an index of in vivo tyrosine hydroxylase activity. Our results demonstrated that ovine prolactin increased turnover of dopamine but had no effect upon tyrosine hydroxylase activation (up to 4 h) in both dorsal and ventral striatal dopaminergic neurons. In contrast, ovine prolacting had a clear effect (within 4 h) on tyrosine hydroxylase activity in mediobasal hypothalamic dopaminergic neurons. These results suggest that ovine prolactin can differentially alter synthesis/release processes of dopamine from these sites.
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PMID:Effects of prolactin on tyrosine hydroxylase activity of central dopaminergic neurons of male rats. 257 30

The relative contributions of dopamine (DA) and prolactin-releasing factor (PRF) in generating the preovulatory prolactin (PRL) surge were investigated. Immature female rats were injected with pregnant mare's serum gonadotropin (PMSG) on day 28. Jugular blood was collected hourly on days 30 and 31. PRL levels were low in the morning of day 30, rose 10-12 times to peak levels from 14.00 to 16.00 h, reached a prolonged plateau from 18.00 to 24.00 h, and reduced to basal levels in the morning of day 31. All PMSG-treated rats ovulated an average of 13-14 ova. PRL levels in age-matched control rats were low throughout this time, and no oviductal ova were present. DA turnover rates in the stalk-median eminence (SME) and posterior pituitary (PP) were determined from the decline in tissue DA after injecting alpha-methyl-p-tyrosine (alpha-MPT), a competitive inhibitor of tyrosine hydroxylase. DA turnover rates increased or were unaltered in the SME and PP, respectively, during the peak PRL phase as compared to presurge rates. In contrast, DA turnover rates were significantly reduced in both tissues during the plateau phase. The turnover rate in the SME, but not the PP, was increased in the morning of day 31. DA turnover rates in control rats never changed. Injection of alpha-MPT to PMSG-treated rats increased PRL levels at all times examined except during the plateau phase. Blood PRL levels were also determined in PMSG-treated rats following posterior pituitary lobectomy or sham lobectomy. The PRL surge was similar in both groups and all rats ovulated.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential alterations in dopamine turnover rates in the stalk-median eminence and posterior pituitary during the preovulatory prolactin surge. 272 44

A 48 h but not a 72 h or 7 day withdrawal from chronic exposure to cigarette smoke was associated with increased noradrenaline levels (quantitative histofluorimetry) in the subependymal layer (SEL) of the median eminence, the anterior periventricular hypothalamic region (PV I) and the parvocellular part of the hypothalamic nucleus (PA FP) and an increased noradrenaline utilization (tyrosine hydroxylase inhibition by alpha MT) in the SEL and the PV I. Following a 48 h or 72 h but not a 7 day withdrawal from chronic exposure to cigarette smoke an increased catecholamine utilization was found in the medial palisade zone (MPZ) of the median eminence. Reduced serum prolactin, FSH and corticosterone levels were found following a 48 h withdrawal from chronic exposure to cigarette smoke. Following a 72 h withdrawal from chronic exposure to cigarette smoke a reduced concentration of serum prolactin was noted. Chronic exposure to cigarette smoke reduced serum TSH levels and lead to a tolerance development with regard to noradrenaline levels and utilization within the preoptic region with the exception of the periventricular preoptic region. The finding of special interest in the present study is the demonstration of a highly significant lowering of corticosterone serum levels despite maintained blood levels of ACTH as seen 48 h following withdrawal. It is suggested that this type of endocrine change may lead to changes in fear-motivated behaviour and contribute to behavioural withdrawal reactions. The maintained reductions of serum prolactin levels found after 48 h and 72 h of withdrawal from cigarette smoke exposure (cf. Andersson et al. 1985a) is discussed in terms of an increased catecholamine utilization in the medial palisade zone of the median eminance. This activation is suggested to be caused by the development of a prolactin receptor supersensitivity within the medium eminence. The present evidence indicates withdrawal effects mainly in the noradrenaline nerve terminals of the subependymal layer of the median eminence, the anterior periventricular hypothalamic region and the parvocellular part of the paraventricular hypothalamic nucleus which inter alia are involved in regulation of ACTH secretion (cf. Andersson et al. 1985a).
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PMID:Effects of withdrawal from chronic exposure to cigarette smoke on hypothalamic and preoptic catecholamine nerve terminal systems and on the secretion of pituitary hormones in the male rat. 273 53

The recently discovered cardiac peptides, called atrial natriuretic factors (ANF), act peripherally as hormones which control fluid and electrolyte homeostasis. Their renal, adrenal and vascular effects are complemented by central nervous system (CNS) actions to inhibit vasopressin secretion, salt preference, and water intake, and to inhibit the CNS component of the hypothalamo-pituitary-adrenal axis. These central actions of ANF are thought to mirror physiological roles played by endogenous, neuronally derived ANF within the brain. ANF immunoreactivity and binding sites in the anterior pituitary gland and median eminence suggest, as well, neuroendocrine actions of the peptide. We have failed to observe direct pituitary effects of ANF on basal or stimulated pituitary hormone secretion; however, specific hypothalamic actions have been discovered. ANF infusions (IV or cerebroventricular) inhibit luteinizing hormone (LH) secretion via, at least in part, an opioid mechanism since naloxone pretreatment blocks the effect. Additionally ANF inhibits catecholamine stimulation of the release of LH-releasing factor in the median eminence. Direct effects of ANF on tuberoinfundibular dopamine neurons are suggested by the observation that the prolactin-inhibiting action of ANF is prevented by domperidone treatment and is absent following alpha methyl-p-tyrosine inhibition of tyrosine hydroxylase activity. These recent results imply neuromodulatory actions of ANF within the CNS that are expressed via interaction with brain peptide and catecholamine systems.
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PMID:Central nervous system actions of atrial natriuretic factor. 284 6

Immunoreactive tyrosine hydroxylase (ir-TH), the rate-limiting enzyme for the synthesis of dopamine and other catecholamines, was localized in the brain and pituitary gland of sexually mature platyfish (Xiphophorus maculatus). This is the first report of ir-TH in the nucleus olfactoretinalis, an LHRH-containing nucleus in the brain which plays an important role in the development and functioning of the reproductive system in platyfish. Ir-TH was also localized in the nucleus preopticus and paraventricular organ. In the pituitary gland ir-TH is found in the prolactin cells and in some fish, in some of the gonadotropin-containing cells of the pars intermedia, but not in the gonadotrops of the pars distalis. The localization of ir-TH in brain centers and pituitary cells associated with reproductive system regulation is discussed in the context of the interaction of monamines, neuropeptides and pituitary hormones during the maturation and operation of the brain-pituitary-gonadal axis.
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PMID:Immunoreactive tyrosine hydroxylase in the brain and pituitary gland of the platyfish. 285 4

Male rats were exposed to cigarette smoke (Walton Horizontal Smoking Machine) from one to four cigarettes (Kentucky reference IR-1 type). Catecholamines in the diencephalon were measured by quantitative histofluorimetry in discrete dopamine (DA) and noradrenaline (NA) nerve terminal systems. Blood TSH, prolactin, LH, FSH, ACTH, vasopressin and corticosterone levels were determined by radioimmunoassay procedures. Exposure to unfiltered, but not to filtered (Cambridge glass fibre filters) cigarette smoke resulted in dose-dependent reductions of NA levels in the various hypothalamic NA nerve terminal systems. Evidence was obtained that exposure to unfiltered but not to filtered cigarette smoke resulted in dose-dependent increases of amine turnover (alpha MT-induced CA disappearance experiments) in the various DA and NA nerve terminal systems in the hypothalamus. The lowering of TSH, LH and prolactin secretion induced by unfiltered smoke were probably induced by nicotine and were independent of tyrosine hydroxylase inhibition. Furthermore, unfiltered cigarette smoke produced a dose-related increase in corticosterone secretion. The inhibitory effects of TSH, LH and prolactin secretion were probably in part related to the ability of unfiltered smoke via its nicotine component to activate the lateral and medial tubero-infundibular DA neurons. The increases in corticosterone secretion may at least in part be related to a smoke induced increase in the facilitatory influence of paraventricular NA nerve terminals on CRF activity.
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PMID:Effects of acute intermittent exposure to cigarette smoke on catecholamine levels and turnover in various types of hypothalamic DA and NA nerve terminal systems as well as on the secretion of adenohypophyseal hormones and corticosterone. 286 16

BALB/cJ mice have more tuberoinfundibular dopamine neurons, and thus greater tyrosine hydroxylase activity, than CBA/J mice. Strain differences in the synthesis and release of prolactin would also be predicted since dopamine released from the tuberoinfundibular neurons is the prolactin inhibitory factor which plays a role in the regulation of both prolactin synthesis and release. As expected, CBA/J mice, with fewer dopamine neurons, synthesized and released significantly more prolactin than BALB/cJ mice; that is, both pituitary and serum prolactin concentrations were greater in CBA/J mice. To determine if there were more cells containing prolactin or more prolactin per cell, pituitaries were stained with antibodies to prolactin and densitometric analysis made of both the average staining per unit area and total staining per pituitary. For both indices CBA/J mice had more staining than BALB/cJ mice. Using these criteria the difference in staining was attributed to more prolactin-stained lactotrophs in the CBA/J strain. Although no differences in the number of acidophils demonstrated by Pearse Trichrome method were observed, acidophils from BALB/cJ mice appeared smaller and contained less cytoplasm than those from CBA/J mice. We conclude that strain differences in the number of tuberoinfundibular dopamine neurons are inversely related to the number of immunocytochemically demonstrable prolactin-containing cells in the anterior pituitary.
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PMID:Strain differences in pituitary prolactin content: relationship to number of hypothalamic dopamine neurons. 286 17

The tuberoinfundibular dopaminergic neurons in the arcuate nucleus of the rat hypothalamus project to the median eminence and release dopamine from the axon terminals into the portal vessels. The released dopamine is transported to the anterior pituitary and acts to inhibit the release of prolactin from lactotrophs. About 50% of the tuberoinfundibular neurons have been shown to have estrogen receptors, and several research groups have shown that estrogen treatment affects dopamine release. Our interest is to determine, using an in vitro run-on transcription assay, whether acute estrogen treatment modulates the expression of the gene encoding for the rate-limiting enzyme for dopamine biosynthesis, tyrosine hydroxylase, in a manner parallel to the values reported for dopamine turnover. We found that after 20 min of estrogen treatment in a 3-week ovariectomized rat that tyrosine hydroxylase gene transcription decreased to 40% of control and continued to decrease after an hour of estrogen to 5% of control. After 4 days of estrogen, tyrosine hydroxylase gene transcription increased but was only about 70% of control. In contrast to the bimodal change in tyrosine hydroxylase gene transcription in response to acute estrogen, we were only able to detect a change in the levels of tyrosine hydroxylase mRNA after 2 weeks of estrogen treatment, when a 2-fold decrease was observed. Similar results for dopamine turnover, as compared to tyrosine hydroxylase gene transcription, have been reported by others in that 3 h after a single estrogen benzoate injection, dopamine turnover was decreased, while after 3 days there was not a significant change. Therefore, it seems that the changes in tyrosine hydroxylase gene transcription after acute estrogen treatment qualitatively parallel the values reported for dopamine turnover, suggesting that the rate of transcription may be an index of neural stimulation.
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PMID:Transcriptional analysis of tyrosine hydroxylase gene expression in the tuberoinfundibular dopaminergic neurons of the rat arcuate nucleus after estrogen treatment. 287 35

The effects of acute continuous exposure to the smoke from 1-4 cigarettes have been studied in the male rat in terms of hypothalamic catecholamine levels and utilization as well as the secretion of anterior pituitary hormones. Catecholamine levels in discrete hypothalamic catecholamine nerve terminal systems were studied by quantitative histofluorimetry. Catecholamine utilization was studied by means of the tyrosine hydroxylase inhibition method using alpha-methyl-(+/-)-p-tyrosine methyl ester. The serum hormone levels of adenohypophyseal hormones and of corticosterone were measured by the use of radioimmunoassay procedures. The results show that acute continuous exposure to unfiltered but not to filtered (Cambridge glass fibre filters) cigarette smoke leads to small but dose-dependent reductions of amine levels in most of the hypothalamic noradrenaline and dopamine nerve terminal system. These effects were associated with an enhancement of regional hypothalamic noradrenaline utilization but not of dopamine utilization in the median eminence. Furthermore, a reduction of TSH and prolactin serum levels was noted as well as increases in ACTH secretion. These results are partly different from those previously obtained with rats acutely exposed to intermittent unfiltered cigarette smoke. This difference is suggested to be due to a temporary blockade of catecholamine release following acute continuous exposure to cigarette smoke.
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PMID:Effects of acute continuous exposure of the rat to cigarette smoke on amine levels and utilization in discrete hypothalamic catecholamine nerve terminal systems and on neuroendocrine function. 288 21

The addition of epidermal growth factor (EGF) to cultures of the rat PCG2 pheochromocytoma cell line increased the level of RNA coding for tyrosine hydroxylase (TH). A region of DNA containing 5'-flanking sequences of the TH gene was fused to a heterologous gene and transfected into a rat anterior pituitary cell line, GH4. The TH gene sequences from +27 to -272 contained information sufficient for the induction of TH by EGF. Two regions within this TH DNA were extensively homologous to the EGF regulatory element of the rat prolactin gene.
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PMID:Regulated expression of the tyrosine hydroxylase gene by epidermal growth factor. 289 99


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