Roberts A B, Frolik C A
Fed Proc. 1979 Oct;38(11):2524-7.
Retinoic acid, a natural metabolite of retinol, has previously been shown to be capable of supporting growth and maintaining proper differentiation in epithelial tissues. Recently, investigation into the in vivo and in vitro metabolism of retinoic acid in hamsters, using both tracheal organ culture and subcellular preparations derived from intestinal mucosa, liver, and testis, has revealed the production of several metabolites more polar than the parent compound. Two of the early products of this metabolic pathway have been identified as 4-hydroxy- and 4-keto-retinoic acid. The formation of these metabolites is maximal in vitamin A-deficient hamsters that have been pretreated with retinoic acid and in vitamin A-normal animals. This fact, together with the decreased biological activity of the two compounds relative to retinoic acid in a tracheal organ culture assay, suggested that oxidative attack at carbon-four of the cyclohexenyl ring may be the first step in the elimination of retinoic acid from tissues. In addition, observations both in vivo and in vitro indicate that all-trans- and 13-cis-retinoic acid at low concentrations may be sharing a common metabolic pathway that includes an isomer of 4-keto-retinoic acid.
视黄酸是视黄醇的一种天然代谢产物，此前已证明它能够支持上皮组织的生长并维持其正常分化。最近，利用气管器官培养以及源自肠黏膜、肝脏和睾丸的亚细胞制剂，对仓鼠体内和体外视黄酸的代谢进行的研究发现，产生了几种比母体化合物极性更强的代谢产物。该代谢途径的两种早期产物已被鉴定为4-羟基视黄酸和4-氧代视黄酸。这些代谢产物的形成在经视黄酸预处理的维生素A缺乏仓鼠以及维生素A正常的动物中最为显著。这一事实，连同这两种化合物在气管器官培养试验中相对于视黄酸的生物活性降低，表明环己烯基环上碳-4处的氧化攻击可能是视黄酸从组织中消除的第一步。此外，体内和体外的观察结果表明，低浓度的全反式视黄酸和13-顺式视黄酸可能共享一条包括4-氧代视黄酸异构体的共同代谢途径。
