Isomyosin redistribution in chronic pressure overload: comparison between peptide mapping and electrophoresis under non-denaturing conditions

Chronic pressure overload induces a redistribution in myosin isoenzymes as demonstrated by Ca⁺⁺-activated ATPase activity, electrophoresis under non-denaturing conditions and immunohistochemistry. We compared, in two groups of renal hypertensive rats and control rats, the isoenzymic patterns obtained by electrophoresis under non-denaturing conditions with those observed after heavy chains digestion with S. Aureus V8 protease. In the hypertensive animals in which a shift towards the "slow" V₂ and V₃ isomyosins was evident, peptide mapping always gave origin to a band which was not present in the controls. Since we consider this peptide as a marker of the redistribution towards the "slow" isoforms, peptide mapping according to Cleveland appears to be a simple and useful method to assess differences in isomyosin composition, at least between hypertrophic pressure-overloaded and normal rat ventricles. Moreover, in our experience this technique is simple, the patterns obtained from highly purified substrates are very reproducible and the digestion allows easy and clear comparisons.