On the Mechanism of Cardiac Glycoside Action
Stimulation of Myosin B Superprecipitation by Ouabain and Digoxin
A study has been made of the effect of ouabain and other cardiac glycosides on a faithful model of contraction, viz. the "superprecipitation" which occurs when ATP is added to a suspension of purified myosin B. Structural changes during superprecipitation were followed by a turbidity method, and rates of ATP utilization with a pH stat. At "optimal" concentrations (ca. 10-9 M and 10-3 M) these substances approximately double the structural and the ATP utilization rates of the myosin B system, but at no concentration do they affect the ATPase of myosin A. In the one case studied, cardioactivity of the substance appeared to parallel its effect in our test system.
- Accepted May 27, 1966.
- © 1966 American Heart Association, Inc.