Chytil F
J Am Acad Dermatol. 1986 Oct;15(4 Pt 2):741-7. doi: 10.1016/s0190-9622(86)70229-6.
Retinoic acid, unlike the naturally occurring vitamin A (retinol), is a minor component of the human diet. It is formed in vivo from retinol and has many metabolites. The biological activity of the metabolites is not higher than that of retinoic acid itself, indicating that the metabolites must be products of retinoic acid catabolism. Little is known about the enzymatic systems responsible for forming retinoic acid or about how it enters the cell. Discovering the molecular mechanism(s) of retinoic acid activity in cellular metabolism is important to understanding its physiologic role. The pharmacologic effects of high doses of retinoic acid may be caused by its action on cellular membranes. Conversely, low concentrations appear to produce physiologic effects. Results of experiments with animals and with cell cultures indicate that the primary physiologic role of retinoic acid is in cellular differentiation. Retinoic acid influences genomic expression, inducing the appearance of some proteins while suppressing the expression of others. The existence of an intracellular retinoic acid-binding protein suggests that it may mediate the physiologic effects of retinoic acid on cellular differentiation.
与天然存在的维生素A（视黄醇）不同，视黄酸是人类饮食中的一种微量成分。它在体内由视黄醇形成，并有许多代谢产物。这些代谢产物的生物活性不高于视黄酸本身，这表明这些代谢产物必定是视黄酸分解代谢的产物。关于负责形成视黄酸的酶系统或其进入细胞的方式，人们了解甚少。发现视黄酸在细胞代谢中的活性分子机制对于理解其生理作用很重要。高剂量视黄酸的药理作用可能是由其对细胞膜的作用引起的。相反，低浓度似乎会产生生理效应。动物实验和细胞培养实验的结果表明，视黄酸的主要生理作用在于细胞分化。视黄酸影响基因组表达，诱导一些蛋白质的出现，同时抑制其他蛋白质的表达。细胞内视黄酸结合蛋白的存在表明，它可能介导视黄酸对细胞分化的生理效应。
