Studies on electrical and mechanical activity in hypoxic papillary muscles of the guinea-pig.

The hypoxia-induced changes in transmembrane potentials and in force of contraction of isolated papillary muscles of the guinea-pig were studied. With different glucose concentrations in the hypoxic medium both the extent and the time course of the reduction in force of contraction and action potential duration could be modified. A time lag of 10 minutes was observed in the onset of action potential shortening. The membrane potential decreased only at advanced stages of hypoxia. Lack of glucose was tolerated for a considerable longer period of time when the preparations were mainly quiescent during hypoxia, although membrane depolarization could not be prevented. Memembrane depolarization was basent only if the mucles were completely unloaded when exposed to hypoxia. The dissociation of events during hypoxia is interpredted as evidence for compartmentalization of energy supply within the cells.