Effects of endocardial endothelium in myocardial mechanics of hypertrophied myocardium of rats

Abstract

Aim: To investigate the effects of endocardial endothelium (EE) in myocardial mechanics of hypertrophied myocardium of rats.

Methods: Hypertrophied myocardium has been developed through long-term renovascular hypertension in rats. Selective stripping of EE was achieved chemically and the effects of EE on the activation and relaxation of hypertrophied myocardium were investigated and compared to those in the presence and absence of intact EE.

Results: Resting tension (RT) and peak developed tension (DT) of isometric contraction of the left ventricular papillary muscles of renovascular hypertensive rats (RHR) remained similar, but maximal rate of tension development and fall (+dT/dtmax and -dT/dtmax) were lowered, time to +dT/dtmax (TPP) and time to -dT/dtmax (TPN) were increased, and time to peak developed tension (TPT) and half relaxation time (RT1/2) were prolonged, vs sham-operated rats (Sham). After EE denudation, TPT, and RT1/2 were significantly abbreviated in RHR. The -dT/dtmax was significantly augmented while the +dT/dtmax was unaltered, resulting in a prominent decrease in the ratio of +dT/dtmax to -dT/dtmax.

Conclusion: EE predominantly influences the relaxation in isolated myocardium and early diastolic filling events in hearts, and is involved in the cardiac compensatory mechanism in hypertrophied myocardium.