摘要:

Superfused dispersed cells respond rapidly to 2- to 10-min pulses of TRH (10-10 to 10-7M) in a dose-dependent manner. The effects of decreasing the stimulus duration can be overcome by a proportional increase in concentration of TRH. A TRH stimulus of 10 min or greater duration results in a sharp peak in TSH secretion followed by a lower plateau. Somatostatin (10-8M) inhibits the response to TRH (5 X 10-9M). T3 (2.0 µg/dl) inhibits TRH-induced TSH secretion by superfused pituitary fragments, but not by dispersed cells. Corticosterone (50 µg/dl), however, inhibits crude CRF-induced ACTH secretion by such cell

ISSN:1663-2818    

DOI:10.1159/000179352

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Administration of exogenous thyrotropin-releasing hormone (TRH) in man leads to an increase in mean arterial blood pressure at 4 and 8 min after TRH. This increase in mean arterial blood pressure is preceded by an increase in plasma norepinephrine levels (maximum response of 274 ± 42 pg/ml vs. basal 158 ± 32, p < 0.01). There was a nonsignificant tendency for epinephrine levels to rise. There was no alteration in plasma renin activity (basal 1.2 ± 0.4 ng/ml/min vs. peak 1.4 ± 0.3) or in plasma aldosterone (basal 5.0 ± 0.6 ng/dl vs. peak 6.8 ± 0.7). We conclude that TRH causes an increase in blood levels of catecholamines in normal man through undetermined mechanisms. The blood pressure changes associated with TRH administration may be related to norepinephrine release. Our findings also lend additional support that acute increases in prolactin have no effect on the renin-angiotensin-aldosterone system i

ISSN:1663-2818    

DOI:10.1159/000179353

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The role of the pineal gland in the regulation of thyroid-stimulating hormone (TSH) secretion was studied in postpuberal male rats using 12:12 h light:dark cycles. Pinealectomy, performed 3–4 days before decapitation, had no effect on the basal or thyrotropin-releasing hormone stimulated TSH secretion, but significantly decreased the cold-induced TSH response both at noon and at midnight. Neither hypothalamic thyrotropin-releasing hormone concentrations nor serum thyroid hormone levels were affected by pinealectomy. Melatonin injected intravenously (1 and 10 mg/kg) or intracerebroventricularly (5 and 50 µg/rat) had no effect on the basal or cold-stimulated TSH levels, neither was the thyrotropin-releasing hormone induced (50 and 125 ng/rat i.p.) TSH response modified by melatonin (1 mg/kg i.v.). Arginine vasotocin (1 and 100 ng/rat) given intracerebroventricularly had no effect on the basal or cold-stimulated TSH secretion. These results suggest that the pineal has no influence on the basal activity of the hypothalamus-pituitary-thyroid system, but it seems that the cold-induced TSH response depends to a considerable degree on the intact pineal gla

ISSN:1663-2818    

DOI:10.1159/000179354

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A growth hormone-secreting tumor (StW5) was implanted into male rats and resulted in a tripling of adrenal weight concomitant with a 30% decrement in pituitary weight. Plasma concentrations of corticosterone in tumor-bearing (TB) rats were significantly elevated at rest or after ACTH injections or the stress of ether anesthesia. The rise in plasma concentrations of corticosterone was due mainly to the large increment in adrenal size although a significant increase in adrenal responsiveness to ACTH was demonstrated in vitro. In addition, plasma corticosterone concentrations were higher in TB rats despite both a doubling of the blood volume and a 50% increase in liver capacity to metabolize corticosterone. Pituitary ACTH content was significantly lower in TB rats, but these pituitary glands could still release near-normal quantities of ACTH as shown both by in vitro incubations and adrenal corticosterone output following ether stress.

ISSN:1663-2818    

DOI:10.1159/000179355

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The age dependence of Leydig cell function was investigated in rats from prepuberty (15 days) to senescence (39 months). Serum LH, serum and testicular testosterone were measured by radioimmunoassay. The binding capacity and affinity of LH/hCG receptors were determined by a radioligand receptor assay (hCG/Leydig cells) using 125I-hCG labelled by the lactoperoxidase method. Separation of bound and free 125I and simultaneous concentration of 125I-hCG was achieved by vacuum ultrafiltration. The biochemical integrity of 125I-hCG tracer was ascertained by various chromatographic procedures. The highest hCG-binding and highest serum LH levels were found during puberty. Serum and testicular testosterone concentrations, however, were maximal in early adulthood. From this period onwards to late senescence hCG-binding changed only slightly, while serum LH and testosterone levels decreased significantly towards late senescence. The study shows that, although hCG binding to the Leydig cell changes characteristically during development, it is minimally affected by aging and cannot therefore be responsible for the reduced androgen biosynthesis in senescence.

ISSN:1663-2818    

DOI:10.1159/000179356

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Male rats received one injection of a ‘subtoxic’ amount of Cd2+ (9.2 µmol/kg body weight) as cadmium chloride and the testes were removed 24 h later. Homogenate fractions of testes that had been freed of ribosomes were tested for their activity in cell-free protein-synthesizing systems using excess exogenous rat liver ribosomes and mRNA. A marked decrease in the incorporation of free [14C]-phenylalanine into peptide was observed with the testes preparations from the cadmium-treated rats. The results indicated that about half of the effect of cadmium was due to decreased aminoacyl-tRNA synthetase activity and the other half was due to decreased binding of [14C]-phenylalanyl-tRNA to ribosomes. The results are discussed relative to the contrasting results obtained in kidney and liver preparat

ISSN:1663-2818    

DOI:10.1159/000179357

出版商:S. Karger AG    

年代:1981

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000179358

出版商:S. Karger AG    

年代:1981

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000179362

出版商:S. Karger AG    

年代:1981

数据来源: Karger