STUDY OF THE HETEROGENEITY OF CREATINE KINASE-MM ISOFORMS USING WESTERN BLOTTING

Objective: To study creatine kinase isoform variants in muscle (skelet al and myocardial) damage using a Western blotting procedure. Design a nd Methods: The study comprised of 16 patients admitted with chest pai n, 14 patients with skeletal muscle damage, and 4 healthy individuals. The creatine kinase-MM (CK-MM) isoforms were separated by isoelectric focusing and detected by electrophoretic transfer to a nitrocellulose membrane and immunoblotting. Binding of the first monoclonal mouse an tihuman CK-MM antibody was detected by either a horseradish peroxidase or alkaline phosphatase anti-mouse immunoglobulin conjugate. Results: Three major variants of CK-MM (MM3 pI = 6.8; MM2 pI = 6.4; MM1 pI = 6 .2) were detected. Minor sub-bands were detected in 4/16 and 3/14 pati ents with acute myocardial infarction (AMI) and skeletal muscle damage , respectively. The tissue form (MM0 pI = 7.14) was visible in 6/16 pa tients with AMI and 4/14 patients with skeletal muscle damage. The app earance of minor variants was therefore of limited diagnostic value in discriminating between patients with and without AMI. Immuno-blotting confirms the parallel increase in mass and activity of CK-MM isoforms , thus confirming measurement of isoform activity as an early marker o f AMI or reperfusion following thrombolytic therapy. Conclusions: Stud y of isoform patterns gives more information concerning AMI and skelet al muscle trauma than is currently available from CK isoenzyme analysi s. However, because CK-MM is also released in skeletal muscle damage, in such instances more discriminant markers of AMI are needed.