Secretory Activity Of Adrenal Cortex Research Articles

Differential expression and function of beacon in the rat adrenal cortex and medulla

Beacon gene is overexpressed in obese rats, and beacon was found to stimulate food intake. Evidence has been recently provided that beacon is also expressed in the endocrine glands of normal rats, including adrenal cortex, of which it appears to regulate secretory activity. To further characterize the role of beacon in the rat adrenals, we investigated the level of beacon expression in the adrenal zona glomerulosa (ZG), zona fasciculata-reticularis (ZF/R) and medulla (AM), and the in vitro secretory responses to beacon[47-73] (hereinafter, beacon) of adrenocortical and adrenomedullary tissues. Real-time polymerase chain reaction revealed similar high levels of beacon mRNA in the ZG and ZF/R, and significantly lower (-80%) levels in AM. Immunocytochemistry showed that the distribution of beacon protein followed that of beacon mRNA. Quantitative high pressure liquid chromatography demonstrated that beacon (5x10(-7) M) reduced by about 56% the in vitro total steroid-hormone production from ZG and ZF/R tissues, without affecting catecholamine secretion from AM specimens. The beacon-induced lowering in the secretory activity of adrenal cortex depended on similar reductions (from 50-64%) in the production of the main adrenocortical hormones (pregnenolone, progesterone, 11-deoxycorticosterone, corticosterone, 18-hydroxy-corticosterone and aldosterone), thereby suggesting an inhibitory action of beacon in the early step of steroidogenesis (i.e. the conversion of cholesterol to pregnenolone). The hypothesis is advanced that beacon is to be considered an autocrine-paracrine negative regulator of mineralo- and glucocorticoid synthesis in the rat adrenal gland.

On the diurnal variation of adrenal cortex hormones. Comparison of persons with thyroid accelerated diseases and normal persons

For several years, we have studied clinically and experimentally the influence of thyroid hormone on secretory activity of adrenal cortex and cortisol metabolism. In this paper the diurnal rhythm of free and conjugated 17-OHCS in plasma and urine, their clearances and the cortisol half-life in hyperthyroid and normal subjects, will be presented.In hyperthyroid patients there was a completely normal diurnal variation in plasma free and conjugated 17-OHCS concentration, the peak values being found early in the morning and the lowest at midnight (Table 3, Fig.3). Urine samples were collected every four hours during 24 hours. The urinary free 17-OHCS excretion in hyperthyroid patients was greater than in normal subjects for all times of the day, but the magnitude of the diurnal variation in hyperthyoid patents was within normal range (Fig.1 Table 1). The urinary conjugated 17-OHCS excretion in hyperthyroid patients was greater than in normal subjects for all times of the day, and was especially elevated in the morning Fig.2, Table 2). Therefore, the magnitude of diurnal variation in urinary conjugated 17-OHCS excretion hyperthyroid patients was greater than in normal subjects. In order to illustrate this phenomenon, we studied the diurnal variation of renal clearance of 17-OHCS and cortisol half-life after infusion of cortisol in hyperthyoroid patients.Plasma sample were collected at 7.00 a.m. and 0.00 a.m., urine samples were collected during the hours from 6.00 a.m. to 8.00 a.m. and from 11.00 p.m. to 1.00 p.m. The renal clearance of free 17-OHCS was greater in hyperthyroid patients than in normal subjects at 0.00 a.m. and 7.00 a.m., while in both cases there was no diurnal variations in the renal clearance of free 17-OHCS (Fig. 5, Tabl 3).The renal clearance of conjugated 17-OHCS was greater in hyperthyroid patients then in normal subjects in the morning as well as at midnigt, and was especially elevated in the morning (Fig. 5, Table 3).These was no diurnal variation in the renal clearance of conjugated 17-OHCS in normal subjects, but in hyperthyroid patients the diurnal variation was observed (Fig. 5, Table 3.) Increased metabolism of cortisol in hyperthyroid patients was observed in the half-life study of cortisol. The removal rate of infused cortisol (50mg) from the plasma of hyperthyroid patients and normal subjects was measured at 8.00 a.m. and 0.00 a.m. The half-lives of plasma cortisol in normal subjects at 8.00 a.m. and 0.00 a.m. were 117.3 minutes and 115.5 minutes. There was no significant difference between these values. The half-life of plasma cortisol in hyperthyroid patients at 8.00 a.m. was 72.5 minutes ; at 0.00 a.m., 90 minutes. There was a significant difference between these values. Therefore, the diurnal variation in the cortisol half-life was not observed in normal subjects, while it was observed in hyperthyroid patients (Fig.6. Table 4).In summary, the increase of the renal clearance of conjugated 17-OHCS and the cortisol disappearance rate in hyperthyroid patients were greater in the morning than at midnight ; these phenomena were not observed in normal subjects.