Abstract
The effect of diphenyihydantoin (DPH) on myocardial Na/K adenosine triphosphatase (ATPase) activity was examined to investigate a potential mechanism of its action in reversing digitalis-induced arrhythmias. DPH was shown to stimulate control ATPase, but only with a high (50/0.2 mM) Na/K ratio through which threshold activation of the enzyme was achieved. In vitro, DPH did not stimulate the partially inhibited enzyme prepared from dogs in which arrhythmias had been produced by infusion of toxic amounts of ouabain. Neither was any reactivation of the ouabain-inhibited enzyme seen when DPH was administered in vivo to reverse toxic arrhythmias produced by ouabain infusion. Furthermore, DPH was ineffective in preventing partial or complete enzyme inhibition produced by ouabain in vitro. Thus, it is suggested that DPH may reverse digitalis-induced arrhythmias through an action other than stimulation of digitalis-inhibited myocardial Na/K ATPase.
Footnotes
- Received June 8, 1971.
- Accepted August 25, 1971.
- © 1971 by The Willams & Wilkins Co.
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