Aortic banding induced in 2-day-old (A2) and 6-day-old (A6) male rats increased the left ventricular (LV) weight after 60 days; right ventricular (RV) enlargement occurred in the A2 group only. The concentration of collagenous proteins in the LV was elevated in both experimental groups (more in the A2 rats) at the expenses of sarcoplasmic proteins. Aortic banding also affected the proportion of collagen types (lower collagen I, higher collagen 111, V) and myosin light chains (higher LC1/LC2) in the LV. Similar changes of proteins in the RV were less pronounced.
The effect of chronic administration of angiotensin converting enzyme inhibitor on the development of hypoxic pulmonary hypertension was studied in rats. Male Wistar rats were exposed for 3 weeks to isobaric hypoxia (10 % O2) and treated with 10 mg/kg b.w. of Ramipril daily. The haemodynamic properties of the pulmonary vasculature were then measured in isolated blood-perfused lung preparation. Ramipril administration during the sojourn in hypoxia resulted in lower baseline perfusion pressure and lower slope of perfusion pressure-flow relationship compared to non-treated hypoxic rats. Partitioning of the distribution of pulmonary vascular resistance across the vascular bed by the occlusion technique showed that it was mainly due to a decrease of arterial and venous vascular resistances to blood flow. It is suggested that Ramipril attenuates the process of morphological reconstruction of pulmonary vasculature by chronic hypoxia rather than the level of vascular smooth muscle tone.