Absorption, storage and distribution of 3-dehydrovitamin A in the rat.

1. The metabolism of 3-dehydroretinal was found to be similar to that of retinal. It alleviated all the symptoms of vitamin A deficiency, and promoted the growth of vitamin A-deficient rats. 2. When administered orally, 3-dehydroretinal was reduced in the intestine of the rat and subsequently esterified and transported to the liver, where it was stored mainly as the higher fatty acid ester. 3. Intraperitoneal administration of the compound led to the accumulation of 3-dehydrovitamin A in liver and other tissues. Subcutaneous administration of the compound showed a good growth response in the rat. 4. The ratio of 3-dehydroretinyl higher fatty acid ester to 3-dehydroretinol in liver, in the post-absorptive state, was nearly 93:7. 5. There was a linear relationship between the 3-dehydroretinol concentrations of blood and liver of rats. 6. Administration of 3-dehydroretinal at a dosage of 7.5mg./day for 3 days brought about hypervitaminosis A in the rat. 7. The maximal retention of 3-dehydrovitamin A by the kidneys was at an optimum dosage of 4.5mg./day for 3 days.