The Minimum Vitamin A and Carotene Requirement of the Rat

Abstract

By means of a vaginal-smear technic and a daily dosing of rats at definite levels with respect to body weight, the minimum levels to prevent vaginal cornification was found to be 3.8 to 4.6 μg. or 18 to 22 I.U. per day of vitamin A per kilogram body weight. Similarly, the minimal carotene level was between 15 and 20 μg. per kilogram body weight. No detectable storage occurred until a level of 80 μg. per kilogram body weight per day was given. Large single doses were less efficiently utilized than daily doses, the efficiency decreasing with increasing size of dose. Simultaneous administration of bile salts with carotene slightly increased its efficiency. The results confirmed previous data on the relation of vitamin-A requirement to body weight. The application of this principle to biological testing in general is discussed, together with the adaptability of the vaginal-smear technic used in these experiments for routine biological testing.