Donoghue S, Kronfeld D S, Ramberg C F
J Dairy Sci. 1979 Feb;62(2):326-32. doi: 10.3168/jds.s0022-0302(79)83243-9.
Effects of mild and severe hypervitaminosis A on retinol transport and clearance were studied in mature ewes. Excessive vitamin A intake was assoicated with high concentrations of vitamin A in plasma and liver, with elevated serum enzymes, with decreased feed consumption and packed cell volume, and with epithelial hyperplasia. Retinol transport in plasma increased 6- to 8-fold with excessive dietary vitamin A, was greater with mild hypervitaminosis A, and increased exponentially with vitamin A concentration in plasma. Clearance of retinol from plasma increased 2-fold with hypervitaminosis A, exhibited a greater response in the mild group, and increased linearly with vitamin A concentration in plasma. The relationship of clearance to vitamin A concentration in liver was described best by a power function. Retinol clearance represents a mechanism to maintain vitamin A concentration in plasma and may be most effective below vitamin A concentrations of 135 microgram/dl plasma. With severe hypervitaminosis A, massive vitamin A accumulates in liver leading to hepatic dysfunction and a resultant decrease in retinol clearance from plasma.
在成年母羊中研究了轻度和重度维生素A过多症对视黄醇转运和清除的影响。维生素A摄入过量与血浆和肝脏中高浓度的维生素A、血清酶升高、采食量和红细胞压积降低以及上皮增生有关。膳食中维生素A过量时，血浆中视黄醇转运增加6至8倍，轻度维生素A过多症时更高，且随血浆中维生素A浓度呈指数增加。维生素A过多症时，血浆中视黄醇的清除增加2倍，轻度组反应更大，且随血浆中维生素A浓度呈线性增加。清除与肝脏中维生素A浓度的关系用幂函数描述最为合适。视黄醇清除是维持血浆中维生素A浓度的一种机制，在血浆维生素A浓度低于135微克/分升时可能最为有效。重度维生素A过多症时，大量维生素A在肝脏中蓄积，导致肝功能障碍，进而使血浆中视黄醇清除率降低。
