COMBINED POSITIVE INOTROPIC INTERACTION OF QUINDONIUM AND OUABAIN

¹ Department of Pharmacoloy, Warner-Lambert Research Institute, Morris Plains, New Jersey

The combined inotropic response to quindonium bromide and ouabain was investigated in vagotomized open chest dogs, using a strain gauge arch for measurement of isometric contractile force. Sequential administration of the maximal effective dose of quindonium and ouabain or vice versa produced a combined effect which did not differ statistically from simple addition of the positive inotropic action of each compound alone. Small doses of pronethalol given rapidly produced a positive inotropic effect, but higher doses reduced contractile force to or near control values. There was a mutual antagonism between the inotropic activity of pronethalol and quindonium such that when pronethalol produced a positive inotropic effect, subsequent administration of quindonium had no effect or reduced contractile force. However, when the contractile force was at control level after pronethalol, quindonium produces a positive inotropic effect. Chronic reserpine treatment attenuated the inotropic action of quindonium but not of ouabain. It was concluded that the inotropic action of quindonium differs in mechanism from that of ouabain and is not the result of beta adrenergicstimulation.