Effect of verapamil on pulmonary hypertension and right ventricular hypertrophy induced in rats by intermittent high altitude hypoxia.

Adult male Wistar rats were used for studying the effect of Ca2+ antagonist verapamil on pulmonary hypertension, right ventricular hypertrophy and the medial thickness of pulmonary arterioles, induced by intermittent high altitude (IHA) hypoxia. This was simulated in a hypobaric chamber (7,000, 8 h daily, 5 days a week, 24 exposures). Verapamil was injected subcutaneously in a single dose of 8 mg/kg before each IHA exposure. Administration of verapamil to IHA-exposed animals significantly reduced right ventricular systolic pressure, right ventricular hypertrophy and pulmonary arteriolar medial thickness. Our results support the hypothesis that the transmembrane influx of extracellular calcium is an important component of the mechanisms of hypoxic pulmonary vasoconstriction.