The response of growth hormone and prolactin of rats to hypoxia.

Effects of acute and chronic hypoxia on growth hormone (GH) and prolactin (PRL) of male rats were studied in a simulated hypobaric chambers at altitudes of 5 km (10.8% O2) and 7 km (7.2% O2), respectively. Acute hypoxia caused decreased plasma GH and increased pituitary GH content; both pituitary and plasma PRL contents at 2 h were decreased and plasma PRL level increased at 24 h. Prolonged exposure of hypoxia (5 km) to 25 days, both pituitary and plasma GH were obviously lower than control and pituitary PRL levels were decreased but plasma PRL increased markedly. The data presented suggest that long-term of hypoxia (10.8% O2) significantly suppresses body growth of rats and inhibits GH release and/or biosynthesis, which may in part correlate with decreased body weight gain; high circulating PRL concentration may be of significance in physiological adaptation to chronic hypoxia.