Release of sarcoplasmic enzymes from frog skeletal muscle

Isolated, intact frog muscles bathed in control saline release creatine kinase (CK) and lactate dehydrogenase (LDH) at constant rates for several hours. The basal rates of release from "toe" muscles (CK 0.087%/min; LDH 0.105%/min) were one order of magnitude greater than those from semitendinosus muscles. This is attributed to differences in muscle mass and geometry, and to the smaller diameter of toe muscle fibers. Enzyme release rates were not affected by Na-free or Cl-free solutions, whereas LDH release rate doubled during exposure to Ca-free (EGTA-containing) saline or in the presence of isosmotic solutions containing 120 mM KCl or potassium propionate. Following mechanical injury or detergent treatment (Brij 58), the enzyme release rates into Ca-free medium reached peak values 4 and 16 times (toe muscle), and 16 and 20-30 times (semitendinosus), respectively, the control rates. The greater effect of detergent treatment is ascribed to a larger area of sarcolemmal damage plus possible changes in the state of the enzymes in the sarcoplasm.