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