Growth retardation in the early developing rat exposed to continuous hypobaric hypoxia.

Weanling male rats weighing 48.5 +/- 1.4 g were divided into two groups, hypoxic and normoxic. The former was placed into an altitude chamber and maintained at a pressure equivalent to 0.45 atm. (6 100 m) over a period of 23 days. The normoxic group was maintained at sea level conditions. Food intake, body weight, body length and tail length were recorded every day. Body weight gain in hypoxic rats was 35% of that seen in normoxic controls at the end of the experimental period. Body length gain was 55% and tail length gain was 59% of normal at the same time. The amount of food eaten by the hypoxic animals during the entire exposure period was 55% of that consumed by normoxic ones. The average daily caloric intake related to metabolic body weight (appetite quotient) of hypoxic rats was 60% of the normoxic control value. Efficiency of protein utilization was not significantly different between both groups of rats. These results indicate that exposure to hypobaric hypoxia induces growth retardation in the rat, which appears to be the result of a diminution in food intake because of a decreased appetite.