No abstract

The effect of intermittent altitude hy- poxia simulated in a hypobaric chamber (7,000 m, 8 h daily, 5 days a week) on the lesser circulation and heart weight was studied in rats. A marked chronic pulmonary hypertension and hypertrophy of the right ventricle after 24 exposures was found. No further rsignificant increase after 60 exposures was reached. Signs of right heart failure were found both after 24 and 60 exposures. 70 days after the removal of the rats from the hypobaric chamber and recovery in normoxic conditions, the right ventricular systolic pressure and right ventricular weight did not differ from controls showing reversibility of pulmonary hypertension and right ventricular hypertrophy even in animals with signs of right heart failure.

No abstract

Adult male rats were used to study the effect of a beta blocking agent on pulmonary hypertension and right ventricular hypertrophy induced by intermittent high altitude (IHA) hypoxia (8 hr daily, 5 days a week, stepwise up to the simulated altitude of 7000 m). Trimepranol was injected subcutaneously in a single dose of 10 mg/kg/b.w. one hour before each IHA exposure. Administration of the beta blocking drug caused significant changes of haematocrit values even in animals kept under normoxic conditions. The initial deep decrease was followed by a slow return to control values; prolongation of treatment led to a further significant decrease of the haematocrit curve. The polycythaemic response of IHA-exposed and Trimepranol-treated animals was, therefore, significantly less pronounced as compared with the hypoxic non-treated group. Administration of Trimepranol to IHA-exposed rats significantly decreased the values of right ventricular systolic and mean pressure, right ventricular hypertrophy as well as the degree of muscularization of pulmonary arteries. It may be assumed that the protective effect of Trimepranol is due to a) changes in pulmonary vascularization, b) reduction of polycythaemia, and c) lower cardiac output, induced by the negative inotropic and chronotropic effect of this drug.