Studies on vitamin A ester: Alcohol partition between the liver, kidneys and plasma of rats

Vitamin A-deficient albino rats either were supplemented daily for 21 days with 13 μg. of vitamin A ester dissolved in cottonseed oil or were dosed orally with different amounts (50–180,000 μg.) of vitamin A ester dissolved in cottonseed oil. Following these treatments, the rats were fed the vitamin A-test diet and, at various time intervals, were sacrified, and kidneys, livers, and plasma were analyzed for vitamin A ester and alcohol. The ester and alcohol were separated chromatographically. Approximately an equal distribution of vitamin A ester and alcohol existed in the kidneys, while in the liver the ester predominated. Both liver vitamin A alcohol and kidney vitamin A (alcohol and ester) either declined very slowly or remained substantially consant during the early and middle stages of depletion of moderate amounts of vitamin A. Also, during this period the content of plasma vitamin A remained relatively the same while the vitamin A ester of the liver was lost rapidly. No correlation was found between the concentration of vitamin A alcohol in either the liver or kidneys and plasma vitamin A alcohol. However, the plasma ester fraction of vitamin A increased with increased dosage and storage of the vitamin in the liver. A close relationship was found between vitamin A alcohol and kidney vitamin A at different levels of vitamin A storage. This study supports the view that plasma vitamin A alcohol is controlled by a mechanism apart from the concentration of vitamin A (ester or alcohol) in the liver or kidneys. It is suggested that certain specialized carrier proteins are responsible for the maintenance of plasma vitamin A alcohol level.