Absorption and Storage of Vitamin A in the Liver of the Rat

Abstract

Equal liver stores of the vitamin were found in both male and female animals when depleted rats were treated for 3 days with large amounts of vitamin A. The relative amount of vitamin A stored in the liver was determined after treatment with increasing doses. At the lowest intake of 63 units per day the liver storage was 11% of the total dose while maximum storage (37%) was obtained at a daily level of 2,000 to 4,000 I.U. Further increase in the amount of vitamin A administered was accompanied by a steady decrease in the efficiency of storage. A comparison was made of the liver storage resulting from treatment with different types of vitamin A preparations. It was found that different lots of cod liver oil, although administered at equal unit levels, produced variable liver reserves of vitamin A. With the exception of some lots of cod liver oil which gave sub-optimal storage, vitamin A was utilized and stored equally well whether fed as a distillate, acetate, halibut liver oil, or saponified concentrate. The storage of vitamin A in the livers of rats following oral, subcutaneous, or intramuscular administration was investigated. The oral method was found to be most effective in producing liver storage. Vitamin A injected subcutaneously was approximately 35% as efficient over a 5-day period as the same amount given orally, while intramuscular injection was only 2% as effective as the oral route. Depleted rats were treated daily for a period of 4 weeks with vitamin A given orally, subcutaneously, and intramuscularly and the increase in growth was measured. It was found that vitamin A distillate was more effective orally than parenterally in promoting growth as well as in producing liver stores.