EFFECT OF INTERMITTENT NORMOXIA ON CHRONIC HYPOXIC PULMONARY-HYPERTENSION, RIGHT VENTRICULAR HYPERTROPHY, AND POLYCYTHEMIA IN RATS

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Abstract
Effect of continuous and intermittent normoxia on chronic hypoxic pulmonary hypertension, right ventricular hypertrophy and polycythemia was studied in rats. After 4 wk in a hypobaric chamber (380 mm Hg), the mean right ventricular blood pressure (.hivin.Prv) was 29.2 .+-. 1.8 (SEM [standard error of the mean]) mm Hg (n [number] = 10) compared to 11.1 .+-. 1.1 mm Hg in 10 untreated control animals. After recovery in room air (24 h/day) for 6 wk, the .hivin.Prv was significantly reduced to 21.2 .+-. 3.5 mm Hg (n = 6). Recovery using intermittent normoxia (8 and 16 h/day) for 6 wk did not reduce .hivin.Prv. In 10 control rats ratio of right to left ventricular weight (RV/(LV + S)) was 28.8 .+-. 1.1%. After 4 wk of chronic hypoxia RV/(LV + S) was 48.5 .+-. 2.4% (n = 10). Recovery using complete normoxia for 6 wk significantly reduced RV/(LV + S) to 32.8 .+-. 1.9% (n = 6). Intermittent normoxia (8 and 16 h/day) did not reduce RV (LV + S). Chronic hypoxia (380 mm Hg) for 4 wk elevated the hematocrit from 35 to 66%. Polycythemia was reversed by recovery using continuous normoxia for 6 wk. Intermittent normoxia (8 and 16 h/day) was ineffective.