Endocrinologia experimentalis最新文献

Inhibitory effect of anterior pituitary tissue implanted into the brain on trophic hormone secretion was studied under resting conditions and after adrenalectomy or ether stress. The weight of pituitary gland in rats bearing anterior pituitary graft in the third ventricle was decreased and the body weight gain was retarded. The levels of ACTH, PRL and GH, but not those of FSH and LH in plasma were significantly lower as compared with all control groups. There was a pituitary ACTH, PRL and GH response to adrenalectomy and ether stress in these rats. Besides supporting literary data on the inhibitory effect of additional pituitary grafts on the adenohypophysis, these findings indicate that pituitary implants did not cause any appreciable alteration of pituitary responsiveness, at least to adrenalectomy or ether stress.

The effect of glucose on insulin removal by perfused liver of fed and fasted rats has been studied. The perfusion medium contained glucose at a concentration of 300 mg/dl or no glucose. It has been found that glucose has no effect on insulin removal in either group and that fasting had no effect on this process. It is concluded that blood glucose concentration does no influence insulin removal by the liver.

The objective of this study was to determine the presence of somatostatin-like immunoreactivity (SSIR) in bovine pituitary intraglandular colloid (IGC) of intermediate lobe (IL) origin. Three colloid samples, sufficient to perform the assays, were taken from freshly slaughtered steers, freed of extraneous tissue and lyophilized. The pools were extracted with acetone and petroleum either and the extract radioimmunoassayed for the presence of SSIR. SSIR was present in two of the three samples assayed. We conclude SS is one of the many peptides found in pituitary IGC of IL origin.

The effect of pinealectomy on the adrenal growth in unilaterally adrenalectomized rats was studied by evaluation of the mitotic activity of adrenocortical cells on the fifth and tenth day after operation. It was found that pinealectomy resulted in an about double increase of mitotic index on the 5th day after unilateral adrenalectomy, and on the 10th day the stimulatory effect of pinealectomy became less significant.

The effect of right- or left-sided vagotomy on serum gonadotropin secretion was studied in rats with two testes and in hemicastrates. Right-sided vagotomy in animals with two testes in situ induced a very marked rise in serum LH levels. Left-sided vagotomy was also accompanied with a slight increase in LH secretion. The difference in serum LH levels between right-and left-sided vagotomized animals was significant. FSH levels were unaffected by either right- or left-sided vagotomy. Removal of the right or of the left testis resulted in a significant increase in serum gonadotropin levels. Unilateral vagotomy in hemicastrates did not alter the hemicastration-induced changes in serum gonadotropin hormone levels. These data indicate that the vagus nerve might have a modulatory role in the control of LH secretion in rats with two testes but not in hemicastrates. The different response in LH levels after right-sided and left-sided vagotomy suggests a functional asymmetry of the vagus nerve in the regulation of LH secretion.

The effects of Pro-thyrotropin-releasing hormone (TRH), pre-pro-TRH (53-74), pre-pro-TRH (83-106), pre-pro-TRH (115-151), pre-pro-TRH (160-169), pre-pro-TRH (178-199) and TRH on thyrotropin (TSH) and prolactin (PRL) release from the rat anterior pituitary were studied in vitro. The rat anterior pituitary was incubated in medium 199 (pH 7.4) with 1.0 mg/ml of bacitracin (medium) for 30 min. The amount of TSH and PRL release into the medium was measured by radioimmunassay. TSH and PRL release from the anterior pituitary was stimulated with the addition of TRH or pro-TRH in a dose-related manner, but not with other peptides. The findings suggest that TRH and pro-TRH stimulate TSH and PRL release from the anterior pituitary in vitro.

Rathke's pouches of 12- and 13-day-old rat embryos were implanted beneath the kidney capsule of adult male rats subjected to the removal of median eminence or to sham-operation. Host animals were sacrificed 28 days after grafting and the implanted pituitaries were processed for immunohistological examination. ACTH, LH-beta, FSH-beta, TSH-beta, GH and PRL immunopositive cells could be observed in fetal grafts of all experimental groups. However, the number and staining intensity of different hormone containing cells largely varied and presumably depended on the hormonal state of host animals. The results indicate that undifferentiated fetal pituitary does not require hypothalamic hypophysiotrophic neurohormones for proliferation and cytodifferentiation and that its development might be modulated by circulating trophic hormones of host animals.

The effects of either a single dose or long-term administration of corticosterone or dexamethasone 21-acetate (Dex Ac) on glucocorticoid receptor concentration in mammary gland cytosol of lactating adrenalectomized rats were investigated. Adrenalectomy on lactation day 7 failed to affect the glucocorticoid receptors significantly. Both the natural and synthetic steroid caused a rapid decrease of receptor binding in the cytosol but the time course of glucocorticoid receptor depletion was different. Complete depletion of cytosol receptor was observed after both a single s.c. Dex Ac dose (20 micrograms/100 g) and after long-term oral treatment (10 micrograms/ml saline as drinking solution for 6 days) immediately after the last steroid dose. In the first case the depletion was still observable at 24 h after the injection without any change in Kd. In contrast, prolonged administration of Dex Ac maintained the receptor binding low even for 48 h after steroid withdrawal and resulted in an increased Kd. Even after an additional day the binding did not exceed the level of 50% of controls. By that time, however, Kd has returned to normal values. On the other hand, a single dose of corticosterone (100 micrograms/100 g) as well as long-term corticosterone treatment (100 micrograms/ml saline as drinking solution for 6 days) reduced the glucocorticoid receptor concentration only to 60% and 25%, respectively. Twenty four hours after the hormone administration the receptor binding returned to control level, no change in Kd being observed. It was concluded that Dex Ac, but not corticosterone, down-regulates the glucocorticoid receptors in mammary gland cytosol of lactating rats.

The influence of a single dose of melatonin administered to pinealectomized and sham operated rats at different times of day on serum T3, T4 concentrations was investigated. It was found that such melatonin influence depends upon a time of day. Both pinealectomy and exogenous melatonin did not influence the thyroid activity in the morning. The most remarkable pineal effect on the thyroid appeared during the night.

TSH receptors in plasma membranes of thyroid nodular and perinodular tissue and the concentration of thyroid hormones and thyroglobulin in serum were estimated in patients with Hashimoto's thyroiditis (HT) and in six persons with scintigraphically cold thyroid nodules (AFN). In perinodular tissue of HT patients specific binding of 125I-bTSH was found to be significantly decreased (1.50 +/- 0.13%; mean +/- S.E.) as compared with AFN patients (2.79 +/- 0.53%), whereas any significant difference in hormone binding to nodular tissues between both examined groups was not detected. Scatchard analysis of TSH binding revealed two kinds of binding sites for both thyroid tissues of all examined patients. The capacity of high affinity binding sites in both thyroid tissues of HT patients was found to be decreased (3.92 +/- 0.86 fmol/mg protein in nodular tissue and 5.93 +/- 1.16 fmol/mg protein in perinodular tissue) in comparison with these tissues of AFN patients (18.80 +/- 18.36 and 32.24 +/- 33.38, respectively). Any differences in dissociation constant and capacity of low affinity binding sites between analysed groups were not observed. Serum TSH levels of HT patients were higher than these in AFN patients and were not significantly changed after surgical treatment. Any difference in triiodothyronine (T3) levels between analysed groups was not detected, while the concentration of thyroxine (T4) was lower in HT than in AFN and significantly decreased after the excision of thyroid gland. Thyroglobulin levels were significantly changed after surgical treatment in both analysed groups.