Semotiadil inhibits the development of right ventricular hypertrophy and medial thickening of pulmonary arteries in a rat model of pulmonary hypertension.

This study was designed to compare the effects of semotiadil, a novel calcium antagonist, with those of diltiazem on the development of right ventricular hypertrophy and medial thickening of pulmonary arteries in a rat model of pulmonary hypertension. Pulmonary hypertension was induced by a single injection of monocrotaline (80 mg/kg). Twenty-four hours later (day 1), oral administration of semotiadil (10, 30, or 100 mg/kg per day) or diltiazem (100 or 300 mg/kg per day) was initiated. The wall thickness of the right ventricle (RV), the RV myocardial fiber diameter, the percent medial pulmonary artery thickness, and the percent area of smooth muscle in pulmonary arteries were determined on day 28. The magnitude of all parameters was significantly less in the group of seven rats that received semotiadil at 100 mg/kg per day than in the group of seven rats treated with diltiazem at 300 mg/kg per day. Semotiadil at 100 mg/kg per day inhibits the development of RV hypertrophy and medial thickening of pulmonary arteries significantly more effectively than diltiazem at 300 mg/kg per day.