Reproductive function in female rats submitted to chronic hypobaric hypoxia.

Female rats were submitted to 5,500 m simulated altitude (50.7 kPa) for 23 weeks in a hypobaric chamber. In vitro biosynthesis of estradiol from labelled pregnenolone was studied in the ovaries of these rats and of their controls at sea level barometric pressure. The weight of the ovaries expressed as mg/rat was 63% higher (p < 0.001) and estradiol biosynthetic capacity expressed as % conversion/rat was 140% higher (p < 0.01) in hypoxic than in control rats. Estrous cycle and fertility were studied in rats submitted to 4,400 m simulated altitude (58.6 kPa) and in their controls. The percentage of estrous was significantly higher in hypoxic than in control animals. The fertility was lower in hypoxic rats. Optical microscopy showed signs of polycystic ovaries in both hypoxic groups. These results may suggest that the normal reproductive function includes oxygen dependent factors.