摘要:

Hypothalamic cell nuclear uptake and binding of 3H-hydrocortisone(3H-HC)-receptor complexes were studied in a cell-free system. Greater net concentrations of radioactivity were found in the 0.4 MKC1 non-extractable fraction (sediment) in the first 20 min of incubation and in the 0.4 MKC1 extractable fraction (supernatant) from 30 to 60 min. Incubation in low ionic strength medium favored localization of radioactivity in the supernatant, whereas high ionic strength promoted greater localization in the sediment. Specific binding in the supernatant was non-saturable, but reached a plateau in the sediment at about 5 × 10–8 M 3H-HC. The observed value of Kd for binding in the nuclear sediment was 4.88 × 109 M–1 and the maximum number of binding sites was 8.8 femtomoles/mg DNA. RNA polymerase activity increased by 59% in the presence of hormone-receptors over that in the presence of free hormone in b

ISSN:0028-3835    

DOI:10.1159/000122824

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Plasma immuno-reactive growth-hormone (RIA-GH) concentrations were investigated under in vivo continuous blood glucose (BG) monitoring after administration of gamma-hydroxybutyrate (GHB) as well as during spontaneous or insulin-induced hypoglycemia. During the narco-analgesia by GHB a marked secretory episode is consistently observed. This secretion peak is not accurately time related with GHB administration and seems to fade off in aging animals. Strictly controlled hypoglycemia elicits a consistent and specific GH release. In contrast deep hypoglycemic levels resulting in a state of metabolic stress inhibit GH secretion. Our results suggest that previous data on the GH regulation pattern during hypoglycemia may depend upon the anesthetic used and/or nonspecific stress responses following deep hypoglycemia. The above mentioned experimental conditions indicate that GH metabolic regulation is not fundamentally different in rodents and primates.

ISSN:0028-3835    

DOI:10.1159/000122776

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Comparisons were made regarding the effects of 50 Hz bilateral electrical stimulation at either 100 or 200 μA applied to the preoptic-suprachiasmatic (POA-SQ) or the arcuate-ventromedial n. (ARC-VMH) regions on prolactin (Prl) and LH plasma levels in male rats under pentobarbital anesthesia. No significant differences were observed in Prl levels between samples obtained either by decapitation, by heart puncture 1 h after pentobarbital administration or by cannulation and sequential sampling with blood cells replacement under pentobarbital anesthesia (35 mg/kg, i.p.)·similar results were obtained with LH. Hormonal values in animals subjected to stereotaxic procedures and electrode penetration (sham controls) had slight but significantly higher Prl levels than the rest of the control groups. LH levels tended to be higher at the end of the experimental period. Stimulation of structures within the POA-SQ region with 100 μA elicited a significant increase by 30 min, with values decaying towards control levels by the end of the experimental period. A similar stimulus applied to the ARC-VMH region failed to promote significant changes in Prl levels. LH plasma values were increased by stimulation applied to either region. With 200 μA applied to the POA-SQ, Prl levels rose higher than with 100 μA and dropped rapidly thereafter. LH values were also significantly increased but levels remained high until the end of the experimental period. Stimulation of the ARC-VMH induced a significant Prl release with high levels persisting during the rest of the experiment, thus giving a response curve different to that one obtained after stimulation of the POA-SQ. LH levels rose to values comparable to those obtained after 100 μA stimulation. It is concluded that the medial preoptic area (MPO), periventricular n., suprachiasmatic n., ventral portions of the anterior hypothalamic area (AHA) contain elements of a neural circuit involved in the control of Prl release in the male rat; that elements within this circuit (as related to Prl control) are apparently different from those in the ARC-VMH (mainly ventral portion of the ventromedial n. and arcuate n.) and that acute conditions do not seem to be as restrictive as in the female rat to obtain Prl release after POA-SQ stimulation. Regarding LH control mechanisms, results are suggestive that neural elements stimulated within the POA-SQ and ARC-VMH regions eliciting LH release belong to the sam

ISSN:0028-3835    

DOI:10.1159/000122777

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Plasma levels of thyrotropin (TSH), prolactin (Prl), growth hormone (GH), thyroxine (T4), and triiodothyronine (T3) were measured in response to continuous 24-h infusion of synthetic thyrotropin-releasing hormone (TRH) in normal and surgically thyroidectomized (THYX) calves in a series of 2 experiments. In the 1st experiment, the low dose of TRH (0.077 μg/min) had no effect on any hormone levels measured. Plasma TSH concentration increased significantly (p < 0.05) in response to TRH infusion (0.77 μg/min) in both experiments, but plasma TSH levels plateaued and then declined in both cases despite continued TRH infusion and irrespective of the presence or absence of a thyroid gland. A similar pattern of secretion, though less markedly decreased over time, was observed for plasma Prl in both experiments. The higher dose (0.77 μg/min) of TRH had no effect on plasma GH concentration in the 1st infusion, but did result in a significant (p < 0.05) increase in overall mean concentration of GH in both normal and THYX calves in the 2nd experiment. Removal of the thyroid gland, thus removing the source of increasing T4 and T3 levels seen in normal calves infused with TRH, failed to alter the secretory patterns of TSH and Prl. These data suggest that feedback inhibition by increasing plasma thyroid hormone concentrations was not responsible for the failure of TSH and, to a lesser extent, Prl to maintain chronically elevated plasma levels in response to continuous 24-h TRH infusion. It is suggested that a depletion of pituitary TSH and Prl stores readily secretable in response to a constant dosage level of TRH may be responsible for the secretory patterns observ

ISSN:0028-3835    

DOI:10.1159/000122778

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Third ventricular injection of dopamine (DA), Piribedil (ET-495), a DA receptor stimulator, norepinephrine (NE), epinephrine (E) and systemic administration of larger doses of DA and the receptor stimulant, apomorphine (APM), were used to evaluate their role in the regulation of TSH and GH secretion in ovariectomized (OVX) as well as ovariectomized, estrogen-progesterone treated (OEP) rats. Intraventricular or i.p. injection of DA or its agonists, ET-495 and APM, caused a lowering of plasma TSH and an elevation of plasma GH concentration in OVX as well as in OEP rats. In contrast, intraventricular injection of NE or E increased plasma TSH and GH concentration. On the basis of these results it is concluded that the central dopaminergic system is inhibitory to TSH secretion, as reflected in our experiments by the significant reduction of TSH levels. On the other hand, the noradrenergic and adrenergic system has a stimulatory role on the release of TRH as evidenced by the increase in plasma TSH levels. Activation of dopaminergic, noradrenergic and adrenergic systems appears to promote release of hypothalamic GH releasing hormone as reflected in the enhanced concentration of plasma GH, but the precise physiological role of these biogenic amines in modulating the release of TSH and GH hormone remains to be elucidated.

ISSN:0028-3835    

DOI:10.1159/000122779

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Impairment of eggs implantation by exposure to alien male during early stages of pregnancy can be completely prevented by blockade of the dopaminergic neurons of the central nervous system (CNS) or by increase of the prolactin (Prl) level in pregnant female mice. Stimulation of serotoninergic neurons delayed the pheromonal effect. Blockade of serotoninergic neurons or treatment by ergocriptine on the 2nd and 3rd day of pregnancy inhibited eggs implantation. These results indicate that Prl release in female mice during the time of implantation is under dopaminergic and serotoninergic control, but pheromonal effect is transmitted by dopaminergic system.

ISSN:0028-3835    

DOI:10.1159/000122780

出版商:S. Karger AG    

年代:1978

数据来源: Karger