Plasma enzyme determinations in normal and dystrophic mice.

The plasma levels of creatine kinase (CK), lactate dehydrogenase and alkaline phosphatase were determined in normal mice of the white CF1 and black C57Bl/6 strains, and in clinically normal, heterozygous and dystrophic mice of the C57BL/6J-dy strain. CF1 mice, 13-130 days old, had an average plasma CK of 152 +/- 58 mIU/ml (mean +/- standard deviation) (n=19). Mice of the C57BL/6 strain had a CK of 164 +/- 39 mIU/ml (n=5). Dystrophic mice, younger than 80 days, had an average CK of 1186 +/- 609 mIU/ml (n=16). The CK levels in plasma from 3 dystrophic mice (99, 99 and 156 days) were 182, 267 and 169 (mean 206) mIU/ml, respectively. CK activities in known heterozygotes (+/dy), 180-200 days old, were 165 +/- 156 mIU/ml (n=7). Up to 80 days of age, 14 clinically normal littermates of dystrophic mice showed two distinct groupings of CK activity. Four animals had a mean of 1136 +/- 418 mIU/ml, while 10 others had a mean CK of 173 +/- 116 mIU/ml. The reasons for the 4 elevated values have yet to be established. Over 80 days of age, the average CK was 152 +/- 63 mIU/ml (n=5). When compared statistically, only the young (less than 80 days) dystrophic and four clinically normal animals, with elevated CK levels, were significantly different from the other six groups of mice examined (p less than 0.001). The data indicate that the plasma CK level in C57BL/6J-dy dystrophic mice is elevated, at least up to about 11 weeks.