Regression speed of cardiac myosin heavy-chain isozyme V3 in loaded right or left ventricle after relief of the load.

Abstract

The authors examined whether there is any correlation between the regression speed of cardiac beta (V3)-myosin heavy-chain (MHC) isozyme and duration of overload. The results showed that in the right ventricle of a 1-week overloaded group, the loaded ventricular MHC isozyme V3 (29 center dot 0 +/- 5 center dot 0%, P < 0 center dot 05) returned to the control level within 1 week after relief of overload (20 center dot 4 +/- 4 center dot 2%, P = NS), whereas in a 3 week overloaded group (32 center dot 8 +/- 5 center dot 3%, P < 0 center dot 05) it took 10 weeks (36 center dot 6 +/- 8 center dot 6%, P = NS). The left ventricle showed the same tendency as the right ventricle. In sham-operated rats, however, the changes in MHC isozyme V3 in the left ventricle were greater than those in the right ventricle. These results suggest that regression speed of the cardiac MHC isoform, changed by pressure overload, is accompanied by the duration of overload. Furthermore, the right and left ventricles may have different responsiveness to MHC isoform transitions in heart stresses.