Identification by isoelectric focusing of creatine kinase-MM isoforms in the plasma and striated muscle of pigs.

Total creatine kinase (CK) and CK-MM isoforms were determined in plasma and longissimus dorsi muscle extracts from normal pigs. Based on their total CK activity, the pigs were divided into two groups. Pigs of group 1 (n = 16) had a mean plasma total CK of 298 +/- 16 U/L and the distribution of the CK-MM isoforms was 65.7 +/- 2.5% CK-MM3, 18.9 +/- 1.6% CK-MM2 and 15.3 +/- 1.5% CK-MM. In group 2 (n = 18; 826 +/- 75 U/L total CK) four isoforms were observed: 3.1 +/- 0.9% CK-MM, 67.9 +/- 3.0% CK-MM3, 21.5 +/- 2.3% CK-MM2 and 7.5 +/- 1.3% CK-MM. The differences between the two groups of pigs were significant (p less than 0.001) for CK-MM1 and the presence of CK-MM. Four CK-MM isoforms were also detected in longissimus dorsi muscle homogenates: 45.6 +/- 8.1% CK-MM, 32.6 +/- 11.7% CK-MM3, 16.6 +/- 2.3% CK-MM2 and 5.1 +/- 2.8% CK-MM1. The release of CK-MM isoforms from muscle into plasma seems to be unrelated to the concentration of these isoforms in striated muscle.