EFFECT OF CORTICOSTEROIDS ON THE CARDIOVASCULAR RESPONSES TO ANGIOTENSIN AND NOREPINEPHRINE

¹ Department of Physiology, University of Virginia School of Medicine, Charlottesville, Virginia

The inotropic and pressor responses to intravenous injections of angiotensin (0.05, 0.2 and 1.0 l.0 µg/kg) and of norepinephrine (0.1, 0.4 and 1.0 µg/kg) were studied. Administration of deoxycorticosterone acetate (DOCA) (5 mg daily for 14 days) significantly enhanced these responses, whereas 2.5 mg of DOCA daily increased the inotropic and pressor responses only at the highest dose level of angiotensin or norepinephrine. Dexamethasone (0.5 mg daily) or cortisol (10 mg daily) failed to enhance any of these effects. Plasma sodium was elevated in those groups of animals which exhibited increased responses. Furthermore, dogs maintained on a high sodium diet for 14 days exhibited an increased response to several of the above variables at several dose levels, whereas dogs on a low sodium diet showed significantly lower responses to all variables at all dose levels. Enhancement of inotropic activity closely paralleled that of pressor effects. The causal relationships of these changes to the plasma sodium ion concentrations are discussed.