Comparison of Effects of Deoxycorticosterone and Dexamethasone on Cardiovascular Responses to Norepinephrine *

Abstract

Cardiovascular responses to graded iv infusions of norepinephrine were observed in 24 dogs that had been treated for 1 week with either placebo, dexamethasone, or deoxycorticosterone. Eight dogs served as control and received daily iv injections of placebo; eight dogs received the mineralocorticoid, deoxycorticosterone; and eight received the glucocorticoid, dexamethasone. The three groups did not differ with respect to base-line hemodynamic variables either before administration of norepinephrine or after autonomic reflexes had been inhibited by ganglionic blockade. Comparisons of the three groups' hemodynamic responses to norepinephrine were made both before and after ganglionic blockade with the parallel line bioassay as a statistical test. Dogs given deoxycorticosterone had much greater increases in mean arterial pressure and peripheral resistance with norepinephrine than did dogs given dexamethasone or placebo. Dogs given dexamethasone had slightly greater increases in mean arterial pressure than did dogs given placebo; changes in peripheral resistance were similar in the two groups. The augmented response of mean arterial pressure was apparent only after ganglionic blockade in the dexamethasone group. The vascular effects of norepinephrine, therefore, were markedly augmented by treatment with doxycorticosterone and only slightly augmented by treatment with dexamethasone. The effect of norepinephrine on mean right atrial pressure was augmented in both groups treated with steroid before hexamethonium but only in the group treated with dexamethasone after hexamethonium. The results indicate that deoxycorticosterone and dexamethasone have different qualitative and quantitative effects on circulatory responses to norepinephrine.