CORRELATION BETWEEN THE INOTROPIC ACTION OF OUABAIN AND ITS EFFECTS ON SUBCELLULAR ENZYME SYSTEMS FROM CANINE MYOCARDIUM

¹ Division of Myocardial Biology and Laboratory of Clinical Cardiovascular Pharmacology, Departments of Pharmacology and Medicine, Baylor College of Medicine, Fondren-Brown Cardiovascular Research and Training Center, Houston, Texas

Right ventricular contractile force and the maximum rate of left ventricular pressure rise were monitored throughout ouabain perfusion of isolated in situ dog hearts. After a 10 to 15% (partial ouabain) or an approximate 45% (full ouabain) positive inotropic effect had been produced, the hearts were washed by an additional three-minute perfusion with chilled saline. Na⁺, K⁺-adenosine triphosphatase (Na⁺, K⁺-ATPase), cardiac relaxing system (CRS) and mitochondria were isolated in relatively purified form from these hearts and from control hearts. The Na⁺, K⁺-ATPase isolated from the partial and full ouabain perfused hearts was inhibited 31 and 59%, respectively. Calcium binding and uptake by CRS and calcium accumulation and oxidative phosphorylation by mitochondria were unaltered compared to control values. Furthermore, in vitro addition of ouabain (10^-7 to 10^-8M) was without effect on CRS or mitochondria from both control and ouabain-perfused hearts. It is concluded that the positive inotropic effect of ouabain occurred concomitantly with an effect on Na⁺, K⁺-ATPase and that no other persistent biochemical alteration was measurable in the subcellular systems investigated.

This article has been cited by other articles:

				T Akera Membrane adenosinetriphosphatase: a digitalis receptor? Science, November 11, 1977; 198(4317): 569 - 574. [Abstract] [PDF]