[The role of glucocorticoids in the cardiovascular adaptation to sodium restriction in the rat].

The role of glucocorticoids (Gs) in the regulation of blood pressure has been examined using an antiglucocorticoid, RU 486, at a dose of 20 mg.kg-1 day-1 X 5 days, in male Wistar rats on a low sodium diet. In unanesthetized and chronically catheterized rats, RU 486 administration decreases mean blood pressure (MBP) by approximately 14 mmHg, without altering growth rate or urinary sodium excretion. Corticosterone administration (1 mg.kg-1 day-1) restores MBP nearly to basal level. Glomerular filtration rate evaluated from inulin clearance is unchanged whereas PAH clearance increases and filtration fraction decreases slightly. In anesthetized rats, RU 486 pretreatment decreases MBP, increases cardiac output (radiolabelled microsphere method), and depresses total and renal vascular resistance. In conclusion, endogenous Gs contribute to blood pressure control in salt-restricted rats, possibly by increasing vascular reactivity to catecholamines and angiotensin.