Calcium augmentation of enzyme leakage from mouse skeletal muscle and its possible site of action.

Creatine kinase efflux from isolated mouse skeletal muscle was monitored in the presence of various concentrations of Ca2+ or La3+ over a 5 hour period. Ca2+ levels between 10(-3) and 10(-2)M augmented enzyme leakage to greater than 300% above control. La3+, which is said to displace Ca2+ from sarcolemmal and t-tubule membranes, depressed enzyme efflux at concentrations between 10(-5) and 10(-3M. These data indicate that extracellular Ca2+ mediates in vitro enzyme efflux, and may be acting on the sarcolemma and its extensions. These observations may prove useful in developing new means to regulate enzyme leakage in various muscle disorders.