Studies in vitamin A. 6. Conversion in vivo of vitamin A aldehyde (retinene1) to vitamin A1

Abstract

Retinene1 (vit. A1 aldehyde) administered to rats orally, subcutan., or intraperiton. is converted into vit. A1 during absorption. This suggests that the alcohol group (either free or esterified) of vit. A1 is essential for its transport and storage. After oral admn. the conversion takes place in the gut, and after subcutan. injn. in the subcutan. tissues. The site of conversion after intraperiton. injn. is uncertain. There is no direct evidence that the liver can convert retinene1 to vit. A1. The conversion represents a simple reduction of the aldehyde. The extracellular spaces of subcutan. tissue contain an enzyme capable of esterifying vit. A1 alcohol. It is suggested that the transformation of beta-carotene into vit. A1 in vivo is more likely achieved by oxidation of the former to retinenei, which is then rapidly reduced to vit. A1, rather than by hydrolytic fission.