PT - JOURNAL ARTICLE AU - Allan M. Lefer TI - CORTICOSTEROID ANTAGONISM OF THE POSITIVE INOTROPIC EFFECT OF OUABAIN DP - 1966 Feb 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 294--299 VI - 151 IP - 2 4099 - http://jpet.aspetjournals.org/content/151/2/294.short 4100 - http://jpet.aspetjournals.org/content/151/2/294.full SO - J Pharmacol Exp Ther1966 Feb 01; 151 AB - A variety of corticosteroids were evaluated as ouabain antagonists in the isolated cat papillary muscle preparation. Aldosterone, 2α-methyl 9α-fluorocortisol, deoxycorticosterone, 9α-fluorocortisol, dexamethasone and corticosterone antagonized the positive inotropic effect of ouabain at 37°C in low-calcium buffer. Cortisol, Reichstein’s Substance S, 11-dehydrocorticosterone, prednisolone and 6α-methylprednisolone did not antagonize ouabain. At concentrations much higher than those of other effective corticosteroids, progesterone also antagonized ouabain. However, this antagonism occurred after a large negative inotropic effect and probably represents a toxic response. At 27°C aldosterone failed to antagonize ouabain, but at this lower temperature aldosterone exerted a much greater positive inotropic effect than at 37°C. A dual receptor mechanism hypothesis is offered to explain tentatively both the inotropic and anti-ouabain effects of aldosterone. The Williams & Wilkins Comapny