Role of nitric oxide in cardiac contractility

ABSTRACT

The aim of the present work was to investigate the direct role of NO, and the possibility that cGMP was its second messenger in cardiac contractility under basal cholinergic and adrenergic stimulated conditions. Experiments were performed on spontaneously beating atrial and electrically stimulated ventricular preparations isolated from rabbits. The results showed that inhibition of NO synthase by nitro-L-arginine had no significant effect on basal atrial or ventricular contractions and that the inotropic effect of acetyl choline or adrenaline did not differ significantly after inhibition of NO synthase. Also, it was observed that L-arginine and sodium nitroprusside decreased significantly ventricular contractions, but atrial contractions were not affected by L-arginine although increased significantly by high concentration of sodium nitroprusside. These effects of L-arginine or sodium nitroprusside were antagonized by the guanylate cyclase inhibitor methylene blue