Defective intracellular calcium handling in monocrotaline-induced right ventricular hypertrophy: protective effect of long-term endothelin-A receptor blockade with 2-benzo[1,3]dioxol-5-yl-3-benzyl-4-(4-methoxy-phenyl-)- 4-oxobut-2-enoate-sodium (PD 155080).

We studied the effect of long-term treatment with the oral endothelin (ET) ET(A) antagonist 2-benzo[1,3]dioxol-5-yl-3-benzyl-4-(4-methoxy-phenyl-)-4-oxobut-2-enoate-sodium (PD 155080; PD) on right ventricular intracellular calcium (Ca(2+)(i)) handling and cardiac and pulmonary artery function in control rats and rats with monocrotaline (MCT)-induced right-heart hypertrophy. Rats were given an intraperitoneal injection of either saline (controls; n = 9) or MCT (50 mg/kg; n = 12), resulting in pulmonary hypertension-induced myocardial hypertrophy, or MCT followed by the daily administration of PD (50 mg/kg) for 9 weeks (n = 9). After 9 weeks, right ventricular pressure was measured, and the hearts were removed and perfused in vitro. Right ventricular function and Ca(2+)(i) transients were recorded simultaneously on a beat-to-beat basis using aequorin. Surviving animals in the MCT group (58%) developed significant hypertrophy and had 2-fold higher right ventricular pressure and a prolonged duration of isovolumic contraction that correlated with a similar prolongation of the Ca(2+)(i) transient, indicating a reduced rate of Ca(2+) sequestration in hypertrophy (P < 0.05 versus control). In the PD group, all animals survived, and right ventricular pressure, diastolic relaxation, Ca(2+) transport kinetics, and peak systolic and end-diastolic wall stress were all normalized (P > 0.05 versus control); and pulmonary artery endothelial function was partly restored (P < 0.05 versus MCT and control groups). These results demonstrate for the first time that long-term ET(A) receptor antagonism normalizes myocardial cytosolic Ca(2+) modulation, which may contribute to the antihypertrophic and cardioprotective effect of ET(A) receptor therapy in this model.