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Effect of Low Environmental Temperature on the Metabolism of Vitamin A (Retinol)¹ in the Rat

Biochemistry-Pharmacology Division, U. S. Army Research Institute of Environmental Medicine, Natick, Massachusetts

The effects of low environmental temperature on liver vitamin A utilization of rats were examined after two, four and six weeks of exposure at 5°. Total liver vitamin A levels were unchanged. The weight gain of animals at 5° was always less than the weight gain at 25°. An increased utilization of vitamin A was indicated if the utilization of the vitamin was expressed as a ratio of the amount of vitamin A removed from the liver to the weight gain of the animal. The increase in the vitamin A depletion ratio observed in the 4-week cold-exposed rats was abolished by administration of thiouracil at a level of 0.1% in the diet. An increased requirement for vitamin A in the cold was indicated by the reduced survival time of vitamin A-deficient rats exposed to cold. In addition, at least 20 times more retinoic acid was necessary to maintain growth and survival in the cold than at 25°.

² This investigation was carried out while P. R. Sundaresan was a National Academy of Sciences — National Research Council Visiting Scientist at the U. S. Army Research Institute of Environmental Medicine.

Manuscript received 20 February 1967.