Isoenzyme distribution of creatine kinase and lactate dehydrogenase in serum and skeletal muscle in Duchenne muscular dystrophy, collagen disease, and other muscular disorders.

We determined the total activity and isoenzyme distribution of lactate dehydrogenase and creatine kinase in serum and biopsy specimens from skeletal muscle of nine normal individuals and nine patients with Duchenne muscular dystrophy (I), five with collagen disease (II), and four with non-progressive unclassified myopathy (III). Mean total serum creatine kinase in patients with Duchenne muscular dystrophy (867 U/liter, SD = 197) was 31-fold that in the control group (28 U/liter, SD = 14). There was also a small (3.3-fold) increase in the mean total serum creatine kinase of patients with III, but none in the serum from patients with II. Changes in the creatine kinase isoenzyme distribution of skeletal muscle were primarily in the MB isoenzyme. The mean percentage of creatine kinase-MB activity in muscle from patients with I (2.81, SD = 1.15) and patients with III (1.69, SD = 1.07) significantly (P less than 0.005) exceeded that of the control group (0.43, SD = 0.18). Muscle from patients with II showed little change. The most striking changes in lactate dehydrogenase were also observed in patients with I, in whom the mean total serum activity (356 U/liter, SD = 115) was 3.4-fold that of serum from the control group (105 U/liter, SD = 19). Skeletal muscle from these patients also showed a significant decrease in mean percent isoenzyme 5 activity (from 50 to 23) and an increase in that of isoenzymes 1 and 2 (from 1 to 9 and 8 to 20, respectively). These changes in the distribution of these two sets of isoenzymes in muscle were reflected in the serum.