Right ventricular hypertrophy and polycythaemia in rats after intermittent exposure to hypoxia

Six groups of 20 male adult rats were maintained in an environmental chamber, each group for a period of 28 days. One group breathed air throughout its experimental period, and a second group breathed a normobaric atmosphere of 12% oxygen. The other four groups were exposed to this hypoxic atmosphere for only a proportion of each 24 h cycle: 2, 4 and 12 h daily, and eight periods of 30 min daily. After 28 days, measurement was made, in each rat, of right ventricule (RV) weight and of red cell mass (RCM) by using 51Cr-labelled rat erythrocytes. In the normoxic control group, RV weight corrected for log body weight in grams was 63.2 +/- 1 mg/log body wt. and RCM was 2.02 +/- 0.05 ml/100 g body wt. This was significantly less than in the group hypoxic for only 2 h each day for 28 days: RV weight 66.6 +/- 0.8 mg/log body wt. (P less than 0.05) and RCM 2.27 +/- 0.05 ml/100 g body wt. (P less than 0.05). Greater increases compared with control were observed in all the other hypoxic groups. There was no significant difference in the increases in RV weight and RCM produced by daily hypoxia in a 4 h continuous period and daily hypoxia in eight 30 min periods. The possible role of intermittent hypoxia in producing polycythaemia and pulmonary hypertension has been the subject of much speculation. Our results show that intermittent hypoxia is a potent stimulus to erythropoiesis and to pulmonary hypertension, reflected in RV hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)