Changes in collagen metabolism in diseased muscle. I. Biochemical studies.

Possible changes in collagen biosynthesis were studied in 50 patients with neuromuscular disorders and 14 controls. Type III procollagen aminoterminal propeptide concentrations and galactosylhydroxylysyl glucosyltransferase (GGT) activities were assayed in serum, and prolyl 4-hydroxylase and GGT activities were assayed in muscle biopsy specimens. All four assays showed significantly elevated values in cases of polymyositis, adult forms of muscular dystrophy, and amyotrophic lateral sclerosis, the concentration of muscular collagen also being significantly increased in the last two conditions. Some abnormalities were also seen in polyneuropathy, myotonia congenita, and undefined myopathy. High correlations were found among the values for the four assays, but no marked correlations with muscular collagen concentration or enzyme activities characteristic of neuromuscular disorders were found. The four assays may reflect changes in actual collagen synthesis in the diseased muscle.