Myosin heavy chain mRNA during the development and regression of myocardial hypertrophy.

RNA synthesis increases during the development and decreases during the regression of pressure-overload induced myocardial hypertrophy. Until now, we have been unable to determine whether these events actually reflected changes in the messenger RNAs for the myosin heavy chain mRNA in the total RNA extracted from rat heart during the development and regression of hypertrophy. We found that the amount of MHC mRNA increased in proportion to the overall increase in total RNA during the development of hypertrophy. However, upon relief of pressure-overload, MHC mRNA decreased to a much greater degree than did total RNA. This is probably related to a sudden cessation of synthesis and the rapid degradation of mRNA. We conclude that the development and regression of myocardial hypertrophy is a function of changes in the mRNA for contractile proteins.