Calcium stimulated enzyme efflux from human skeletal muscle

Calcium stimulated efflux of four enzymes from human rectus abdominis muscle was studied in vitro. The ratio of efflux of creatine kinase (EC2.7.3.2) increased with increasing calcium concentrations reaching a maximum level with 5mM calcium of 1.9 times that in the absence of calcium. Lactate dehydrogenase (EC 1.1.1.27) efflux at this calcium concentration increased to 2.6 times that in the absence of calcium. However, alanine aminotransferase (EC 2.6.1.2) and aspartate aminotransferase (EC 2.6.1.1) showed a slower increase in the rate of efflux in the presence of 5OmM calcium reaching levels of only 1.3 and 1.5 times respectively that in the absence of calcium. These observations suggest that calcium may be involved in augmenting enzyme efflux from human muscle and may therefore be of relevance in the pathogenesis of Duchenne muscular dystrophy.