Endothelin receptor antagonists in 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 beagle model of pulmonary hypertension. Background. We recently developed beagle model of pulmonary hypertension that allows accurate determination of cardiopulmonary hemodynamic variables and is associated with elevated plasm 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 ET 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 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 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. ET receptor antagonists decrease pulmonary artery pressure in beagle model and may therefore be clinically useful for treatment of pulmonary hypertension.