Action of Ouabain on Isometric Twitch Tension in Striated Muscle.

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Abstract
Summary Ouabain significantly increased the isometric twitch tension of the indirectly stimulated rat diaphragm. The diaphragm was analyzed for sodium, potassium and calcium content following exposure to ouabain, exposure to ouabain plus indirect stimulation of the muscle, and the effect of indirect stimulation alone. 1. In the resting diaphragm increasing increments of ouabain (0.5, 1, 2 and 4 μg/ml) resulted in a significant gain in muscle Na, a significant loss of K but no change in Ca as compared to the resting, non-ouabain treated muscle. 2. In the stimulated diaphragm the same increments of ouabain resulted in a significant increase in Na and Ca content of the muscle and a significant loss in K as compared to the resting, non-ouabain treated muscle. In the control stimulated diaphragm there was also a significant gain in Na and Ca content of the muscle and a significant loss in K as compared to the resting, non-ouabain treated muscle. The greatest shifts in Na, K and Ca occurred in the stimulated muscle in the presence of the cardiac glycoside.