Endothelin receptor antagonists in a beagle model of pulmonary hypertension: contribution to possible potential therapy?

OBJECTIVES This study investigated the pharmacologic effect of endothelin receptor antagonists on cardiopulmonary hemodynamic variables in a beagle model of pulmonary hypertension. BACKGROUND We recently developed a beagle model of pulmonary hypertension that allows accurate determination of cardiopulmonary hemodynamic variables and is associated with elevated plasma endothelin-1 concentrations similar to those in pulmonary hypertension in humans. METHODS Twelve beagles (pulmonary hypertension, n = 6; control group, n = 6) were studied during baseline conditions and during right atrial infusion of FR139317 (an ETA receptor antagonist), RES-701-1 (an ETB receptor antagonist), nitroglycerin and prostaglandin E1. Pulmonary hypertension was induced in experimental beagles 8 weeks after injection with 3 mg/kg body weight of dehydromonocrotaline. RESULTS FR139317 lowered pulmonary artery and systemic arterial pressures in both pulmonary hypertensive and control beagles, with a significantly greater effect on pulmonary artery pressure in pulmonary hypertensive dogs. RES-701-1 tended to increase pulmonary artery pressure only in pulmonary hypertensive beagles. Nitroglycerin depressed pulmonary artery and systemic arterial tone equally well in control and pulmonary hypertensive animals. Prostaglandin E1 produced a greater decrease in systemic arterial pressure in pulmonary hypertensive than in normal beagles despite having the same effect on pulmonary artery pressure in both. CONCLUSIONS ETA receptor antagonists decrease pulmonary artery pressure in a beagle model and may therefore be clinically useful for treatment of pulmonary hypertension.