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来源人体的维生素D主要来自饮食中的D_2,D_3.维生素D是一种脂溶性维生素,存在于鱼肝油、卵黄内;部分来自自身皮肤产生的D_3。但维生素D_2和D_3尚非真正发挥维生素D作用的物质,它需要经过两个羟化反应才能发挥生理作用。维生素D由皮肤或肠道转运至肝脏,在C_(25)位上羟化转变成25(OH)D_3,然后再经过肾脏转变成活性最强的维生素D代谢产物1,25(OH)_2D_3。肾脏的羟化反应是由1-羟化酶完成的,主要是发生在肾近
Source of vitamin D from the body mainly from the diet D_2, D_3. Vitamin D is a fat-soluble vitamins, exist in cod liver oil, egg yolk; part of their own skin to produce D_3. However, vitamin D 2 and D 3 are not really substances that act as vitamin D. They require two hydroxylation reactions to exert their physiological effects. Vitamin D is transported from the skin or intestine to the liver and is hydroxylated at 25 (OH) to 25 (OH) D_3, which is then converted to the most potent vitamin D metabolite 1,25 (OH) _2D_3 by the kidneys. Hydroxylation of the kidneys is done by 1-hydroxylase, mainly in the kidney