Serum factors influencing creatine phosphokinase. In vitro studies using diffusates.

In vitro studies with diffusates obtained following dialysis of serum samples have enabled us to confirm the presence of inhibiting and activating factors influencing CPK activity. Activating factors are commonly found in many neuromuscular disorders like Duchenne muscular dystrophy (DMD), spinal muscular atrophy and hypothyroid neuromyopathy, and inhibiting factors in dermatomyositis. These findings are further elaborated during serial serum CPK studies after EMG in 3 cases of neurogenic atrophy and 1 case of DMD. The in vivo inhibitory and activating influence of serum factor(s) at 96 and 160 hr respectively after EMG was confirmed by in vitro studies with the diffusates of these serum samples. The functional variations of these diffusates are shown to be related to differences in the composition of these diffusates suggested by paper chromatography.