Disparate effects of diethylstillbestrol and prednisolone on enzyme efflux from heart and skeletal muscle.

We have previously shown that diethylstilbestrol (DES) almost always, and prednisolone (Pr) less frequently, lowered the high serum enzyme activities in Duchenne's muscular dystrophy (DMD). In experimental studies, it was shown that pretreatment of mice with each of these agents lowered enzyme efflux from isolated skeletal muscle incubated in vitro, but efflux was augmented by higher doses of Pr. This suggested that these agents may influence skeletal muscle enzyme efflux in man also, producing the effects noted in DMD. The present studies were undertaken to assess the effect on enzyme efflux from skeletal muscle and heart that these two agents would exert when given in combination. Four groups of mice (14/group) were injected with saline, 250 mug DES, 35 mug Pr, or 250 mug DES plus 35 mug Pr in saline every other day for 22 days. The left gastroecnemius and heart were isolated from animals of each group, and placed in separate tubes containing incubation medium at 25 degrees C. The efflux of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) which issued from each organ was determined over a 5 hour period. In the doses tested, it was found that: 1) DES selectively reduced enzyme efflux from skeletal muscle, but had no effect on enzyme efflux from heart; 2) a Pr dose which decreased enzyme efflux from the heart, augmented efflux from the gastrocnemius; and 3) DES prevented the enhanced enzyme efflux produced by Pr. These studies indicate that these hormones, in pharmacological doses, influence enzyme efflux from muscle. This suggests, but it is not established, that these hormones also exert a similar physiological role. Finally, this experimental model appears to be useful in assessing the effects of single agents, and agents in combination, on enzyme efflux, and should be of aid in selecting appropriate agents which may be therapeutically useful in Duchenne's muscular dystrophy.