LIVER RESERVES OF VITAMIN A AND THEIR RELATION TO THE SIGNS OF VITAMIN A DEFICIENCY IN THE ALBINO RAT

Abstract

Groups of weanling albino rats fed a vit. A-deficient diet supplemented with 10, 15, 20, 30, 50, and 80 units of vit. A per. kg. body wt., respectively, showed that growth was sub-normal at the 2 lowest levels in both [male][male] and [female][female]. During the 9 wks. im-mediately following weaning, [female][female] showed significant im-provement in growth rate when the intake was raised from 30 to 50 and from 50 to 80 units/kg., [male][male] only when the intake was raised to the 80-unit level. During the next period the [female][female] show no significant difference while the [male][male] had an enhanced growth rate at the higher levels of dietary vit. A. The scotopic visual threshold of normal albino rats, as detd. by a brightness discrimination test, lies between log 2.6-35 [mu][mu] lamberts. Hemeralopia appears as the first detectable sign of vit. A deficiency, followed closely by continuous cornification of the vaginal contents of the [female][female]. [female] animals appear to deplete more rapidly than [male][male] in spite of larger liver reserves, and the vit. A stores of the liver are practically exhausted before hemeralopia appears. No quantitatively measurable stores of vit. A can be demon-strated in the livers of rats fed less than 50-80 units of vit. A/kg, body wt./day. This is about 4 times the amt. usually considered as the "minimum" requirement for the rat. Some considerable need of the body must be met in an apparently normal animal before liver storage occurs. More sensitive physiological indicators of vit. A deficiency probably remain to be discovered, and the "minimum" vit. A requirement may be somewhat higher than 20 units/kg. body wt./day.