The Anorexic Effect of High Altitude on Weight Gain, Nitrogen Retention and Body Composition of Rats

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Abstract
The effects of translocation to high altitude on growth rate, nitrogen retention and body composition were studied in meal-eating albino rats. Ad libitum-fed, meal-eating rats were rapidly (2.25 hours) translocated from Denver (1,600 meters) to Pikes Peak (4,300 meters), Colorado, and were killed 2, 6 or 14 days later. Identical ad libitum and pair-fed, meal-eating control groups were transported for a similar period within the Denver area. An initial sacrifice group was not transported. Transportation stress suppressed growth of the control animals during the transport day even though pretransport food intake was normal. Additionally, the group translocated to Pikes Peak lost more weight on transport day than either control group. Transportation stress depressed (26%) the food intake of the ad libitum control animals for approximately 24 hours. Translocation to high altitude reduced food intake 58% during day 1, 27% during the next 5 days and 16% during the last 7 days. The high altitude animals lost more weight and body nitrogen on day 1 and gained less weight and retained less nitrogen throughout the entire experimental period than the ad libitum control animals. The reduction in weight gain and nitrogen retention was primarily attributed to reduced food intake. The body weight changes of the high altitude and pair-fed groups were identical through day 10 and the urinary nitrogen excretions were similar throughout the study. The high altitude animals accumulated less carcass water, fat, protein and ash than the ad libitum control animals. This decrease primarily reflected the total growth depression due to the altitude-induced anorexia. Only minor differences were observed when composition was expressed as a percentage of carcass weight or fat-free mass.