Abstract
Summary
Experiments were conducted on the effects of graded doses of vit. A on resistance to low environmental temperature and x-irradiation injury in the male rat. The average survival time of rats depleted of vit. A was 1.9 days at an environmental temperature of 2°C and 19.3 days under standard laboratory conditions (23 °C). Adjustment to low environmental temperature (as judged by per cent surviving an experimental period of 30 days) was significantly increased in animals fed an average daily intake of 2.5 U.S.P. units of vit. A, but a minimal intake of approximately 5 U.S.P. units of vit. A daily was required for optimal adjustment to cold. A direct correlation was observed between the vit. A content of the diet and resistance to x-irradiation. All rats administered an average intake of 2.5 U.S.P. units of vit. A daily succumbed following a single exposure of 750 r x-irradiation; 90% of the rats receiving a daily intake of 50 U.S.P. units of vit. A and exposed to a similar dose of x-irradiation survived. An average daily intake of 10 U.S.P. units of vit. A was inadequate for optimal resistance to x-irradiation, although this level of vit. A was adequate under standard laboratory conditions for optimal growth.
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