[Mineralocorticoid function of the rat adrenal gland and thyroid hormones]

Adrenal mineralocorticoid function was studied in 195 male albino Wistar rats with a different level of thyroid hormones in the organism. Aldosteronemia, aldosteronuria, and plasma renin activity were studied in in vivo experiments. In vitro experiments were carried out to study the content of aldosterone in the adrenals and its discharge into the incubation medium in euthyroid, hyper- and hypothyroid animals. Hyperthyroidization leads to manifest inhibition of the adrenal mineralocorticoid function, and suppresses aldosterone excretion in the urine and plasmic metabolic clearance in diminished formation of aldosterone in the glomerular zone. Changes of an opposite character occur in the renin-angiotensin-aldosterone system of rats after total thyroidectomy. Injection of small doses of thyroxine also reduces aldosterone production in the adrenals of thyroidectomized animals. It is shown that an excess of endogenous thyroxine in the organism produces an inhibiting effect not only on the level of aldosterone production and secretion, but, to a definite measure, also on the level of the possible realization of its peripheral action.