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Environmental Temperature and the Utilization of ß-Carotene by the Rat¹

Department of Biochemistry and Nutrition, University of Nebraska, Lincoln, Nebraska 68503

The effect of environmental temperature on ß-carotene utilization by the rat was evaluated by liver vitamin A storage bioassay. Exposure of rats to 5° consistently elevated the biopotency of ß-carotene relative to retinyl acetate when compared with a 25 or 35° environment. A study with retinaldehyde and triiodothyronine suggested that the stimulatory effect(s) on ß-carotene utilization occurred either in the cleavage or absorption of ß-carotene from the intestine. The method of administration of the test materials influenced the magnitude of the effects. Techniques which resulted in poor utilization of vitamin A and ß-carotene increased the differences between the temperatures. The small differences associated with methods resulting in high utilization of ß-carotene (given as a component of the diet) indicate that environmental temperature is of minor importance as a factor influencing the conversion of ß-carotene to vitamin A.

KEY WORDS: • environmental temperature • ß-carotene • vitamin A • retinyl acetate • triiodothyronine • retinaldehyde

¹ Published with the approval of the Director as paper no. 2942, Journal Series, Nebraska Agricultural Experiment Station. Some of these data are from a dissertation presented by John Edgar Smith to the Graduate College of the University of Nebraska in partial fulfillment of the requirements for the Ph.D. degree. An abstract of these data was published in Federation Proc. 29: 292 (1970).

² Present address: Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, N. Y. 10032.

Manuscript received 13 July 1971.