Steroid biosynthesis by gonads of rats submitted to chronic hypobaric hypoxia

In vitro biosynthesis of steroids by testes and ovaries was studied in rats submitted to 6,000 m simulated altitude for 23 weeks and their controls at sea level atmospheric pressure. Gonads' homogenates were incubated in the presence of 4(-14) C-pregnenolone and cofactors. Extractions, partitions, paper chromatography and finally crystallizations until constant specific activity were performed. Tritium labelled internal standards were used to correct for methodological losses. In male animals, only androstenedione biosynthesis calculated per rat as well as the weight of the testes were reduced in hypoxia. Nevertheless, this reduction was accompanied by an equivalent decrease in body weight; testosterone biosynthesis was not significantly changed. On the contrary, in females, estradiol biosynthesis and the weight of the ovaries were significantly higher in hypoxic than in control animals. Macroscopic and microscopic aspect of the ovaries in hypoxic rats also indicate a hyperactivity of the steroidogenic function. Weight curves and mortality studies confirmed previous findings about the advantage of females in adaptation to hypoxia. Results show that ovaries play an active role in this process.