THE INHIBITION OF ANGIOTENSIN-CONVERTING ENZYME ATTENUATES THE EFFECTS OF CHRONIC HYPOXIA ON PULMONARY BLOOD-VESSELS IN THE RAT

The effect of chronic administration of angiotensin converting enzyme inhibitor on the development of hypoxic pulmonary hypertension was stu died in rats. Male Wistar rats were exposed for 3 weeks to isobaric hy poxia (10% O-2) and treated with 10 mg/kg b.w. of Ramipril daily. The haemodynamic properties of the pulmonary vasculature were then measure d in isolated blood-perfused lung preparation. Ramipril administration during the sojourn in hypoxia resulted in lower baseline perfusion pr essure and lower slope of perfusion pressure-flow relationship compare d to non-treated hypoxic rats. Partitioning of the distribution of pul monary vascular resistance across the vascular bed by the occlusion te chnique showed that it was mainly due to a decrease of arterial and ve nous vascular resistances to blood flow. It is suggested that Ramipril attenuates the process of morphological reconstruction of pulmonary v asculature by chronic hypoxia rather than the level of vascular smooth muscle tone.