Bondi A, Sklan D
Prog Food Nutr Sci. 1984;8(1-2):165-91.
Vitamin A, an unsaturated 20 carbon cyclic alcohol, subserves a number of important physiological functions. However, the biochemical basis of these roles is not well understood. The main sources of retinol are liver, egg yolk and milk fat. Several carotenoids show vitamin A activity. The conversion of beta-carotene to retinol is affected by copper-containing dioxygenase and zinc-containing retinene reductase. The efficiency of conversion varies in different species. The latter is defined in units as the daily dose required to produce a weight gain of 3 g/week in young rats between the 4th and 8th week. Retinol is unstable on exposure to light or heat, particularly in the presence of heavy metal ions and water. Much recent work has focused on the absorption, metabolism and excretion of vitamin A. It is now recognized that plasma vitamin A levels do not reflect the nutritional status except in severe hypo- and hypervitaminosis A. Also, many dietary factors may influence vitamin A metabolism. These basic and applied aspects of vitamin A are reviewed.
维生素A是一种不饱和的20碳环醇，具有多种重要的生理功能。然而，这些作用的生化基础尚未得到充分理解。视黄醇的主要来源是肝脏、蛋黄和乳脂。几种类胡萝卜素具有维生素A活性。β-胡萝卜素向视黄醇的转化受含铜双加氧酶和含锌视黄醛还原酶的影响。不同物种的转化效率各不相同。后者以单位定义为在第4至8周龄的幼鼠中每周体重增加3克所需的每日剂量。视黄醇在光照或加热下不稳定，特别是在重金属离子和水存在的情况下。最近的许多工作都集中在维生素A的吸收、代谢和排泄上。现在人们认识到，血浆维生素A水平不能反映营养状况，除非在严重的维生素A缺乏和过量的情况下。此外，许多饮食因素可能影响维生素A的代谢。本文综述了维生素A的这些基础和应用方面。
