Further studies on creatine kinase activity in human skeletal muscle.

Creatine kinase (CK) was measured in muscle samples from 9 female and 9 male adult subjects using comparatively two procedures. The improved method, using N-acetylcysteine as activator gives results about 1.5 times higher than that with reduced glutathione. The significant correlation existing between activities of CK and hexosephosphate isomerase was confirmed using the improved method. There also exists a correlation between CK and enolase activity. In this respect, there are no differences between muscle samples from male and female subjects.