Contractile behavior of rat myocardium after reversal of hypertensive hypertrophy.

The effects of renovascular hypertension and its reversal on the contractile performance of papillary muscles from rats has been examined. Hypertension of 10 wk duration caused a 48% increase in heart weight and significant prolongations of isometric time to peak tension (TPT), time to half relaxation, and time to peak shortening (TPS). A significant depression in the velocity of shortening was observed in the 10-wk group. However, muscles from hypertensive rats were still able to maintain normal levels of peak isometric developed tension and peak shortening; this may be due to the observed prolongation of TPT and TPS, respectively. In addition, calcium-activated actomyosin ATPase activity was depressed in hearts of hypertensive animals. Reversal of hypertension was studied at 20 wk after the onset of hypertension (10 wk of hypertension followed by 10 wk of normotension). Contractile and biochemical alterations observed in hypertensive animals were reversed in rats undergoing this regime. Thus reversal of a gradually applied pressure overload resulted in the regression of mechanical and biochemical abnormalities associated with the pressure overload myocardial hypertrophy.