The destruction of vitamin A by blood

In recent studies of the metabolism of vitamin A and carotene the technique of intravenously injecting aqueous dispersions of these substances has frequently been used (Bieri & Pollard, 1954;Kon, McGillivray & Thompson, 1955 ;McGillivray, Thompson & Worker, 1956;Worker, 1956Worker, , 1957)).The interesting observation was made by Kon et al. (1955) that when vitamin A alcohol was given intravenously to rats and rabbits the vitamin quickly disappeared from the circulation.Only one-fourth of the dose was found in the livers of rats after 15 min.In studying this aspect of vitamin A metabolism in more detail, we have determined the distribution in the body of injected vitamin A and also its rate of destruction by various organs.It has been found that vitamin A is destroyed faster when incubated with the blood of young rats than with that of old rats.The destruction is associated with the red blood cells. EXPERIMENTAL AND RESULTS Preparation of vitamin A dispersionsCrystalline vitamin A acetate (Distillation Products Industries, Rochester, N.Y .) was dissolved in warm 95 % ethanol, Tween 40 (polyoxyethylenesorbitan monopalmitate, Atlas Powder Co., Wilmington, Delaware) added, and the solution diluted with 0.9 yo saline to give final concentrations of 12.5 yo ethanol and 5 % Tween. Animals and dietsRats used for injection of vitamin A were males obtained from the Holtzman Company (Madison).They were maintained on a purified vitamin A-free diet (Bieri & Sandman, 195 I) and used for experiment when the first signs of vitamin A deficiency were manifested (body-weight, 100-150 g).Rats used in the blood studies were of the Holtzman strain, but were obtained from the stock colony of the National Institutes of Health.They were maintained on commercial pellets.Mice and rabbits also were from the stock colony.Chicks and guinea-pigs were from experimental groups fed on various complete purified diets.The solutions of vitamin A acetate were administered to rats orally by stomach tube or intravenously through the tail vein while the animal was under light ether anaesthesia.Blood was collected from rats and mice by decapitation or heart puncture; heart puncture was used for guinea-pigs, rabbits, and chicks.