Abstract
Summary
The K-contracture in isolated rabbit atria is transient in nature, resembling qualitatively that seen in single skeletal muscle fibers, but differing from that found in frog ventricle. Tension development is accompanied by an increase Ca45 entry with no detectable change in tissue Ca content. The rate of rise of tension, the level of peak tension and the rate of decline of tension is increased by ouabain. It was concluded that K releases an activator (probably Ca) from a precursor stored at a cellular site, and then is rapidly inactivated; the contraction lasting until the precursor is exhausted. Ouabain is believed to act by promoting the release of activator and possibly by reducing the rate at which the precursor is reformed at its storage site.
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