Effect of pretreatment with prednisolone on enzyme efflux from isolated skeletal and heart muscle.

In a previous study, the efflux of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) which takes place from isolated mouse skeletal muscle was shown to be significantly reduced by pretreatment of the intact animal with diethylstilbestrol (DES). This compound is known to reduce the high serum enzymes present in patients with Duchenne's muscular dystrophy (DMD). Glucocorticoids also reduce the serum enzymes in DMD. The purpose of this study was to determine if pretreatment with the glucocorticoid, prednisolone, also lowered the efflux from isolated mouse skeletal and cardiac muscle. The results of these studies show that prednisolone pretreatment lowers the enzyme efflux from isolated skeletal muscle, but not from heart. There is an optimal dose which produces this reduction, which if exceeded, augments the efflux. Thus two agents are now known which lower the efflux of CPK and LDH from isolated skeletal muscle. These same two agents lower the high serum enzymes in DMD. This suggests, but does not prove, that the mechanism by which these agents lower the serum enzymes in DMD is by reducing enzyme efflux from skeletal muscle.