RIGHT-VENTRICULAR CONTRACTILE PROTEIN FUNCTION IN RATS WITH LEFT-VENTRICULAR MYOCARDIAL-INFARCTION

We studied contractile function in cardiac trabeculae isolated from th e right ventricles (RV) of rats with experimental heart failure (HF) i nduced by left ventricular (LV) myocardial infarction (24 wk post-MI; n = 6) and from sham-operated rats (n = 7). Sarcomere length (SL) was measured by laser diffraction techniques, and force (F) was measured b y silicon strain gauge. SL was kept constant at all times by computer feedback control. HF was associated with marked LV dilation and pulmon ary congestion. In intact, RV twitching trabeculae, HF was associated with a depression of the F-SL relation at extracellular Ca2+ concentra tion ([Ca2+](o)) = 1.5 mM and a depression of the F-[Ca2+](o) relation at SL = 2.0 mu m. HF was also associated with a significant depressio n of the F-intracellular [Ca2+] relation at SL = 2.0 pm measured after chemical permeabilization of these RV trabeculae (skinned fibers). Ou r results suggest that reduced force development in this model of HF i s due, in part, to depressed function of the contractile filaments.