一、活性代谢物的生理作用众所周知,维生素D的生理作用是(1)小肠对钙的吸收;(2)肾对钙离子的再吸收;(3)从骨溶出钙和磷酸以及(4)骨的钙化。但近十年来的研究表明,这些作用不是维生素D而是1,25-(OH)_2D_3引起的。 D_3在肝代谢为25-OH-D_3,这是血中的主要代谢物,但它被肾进一步代谢为1,25～(OH)_2D_3或24,25-(OH)_2D_3等。血钙浓度高或维生素D含量充足时,可代谢为24,25-、23,24-及25,26-(OH)_2D_3,23,25-(OH)_2D_3还可被代谢为25-OH-D_3 26,23-内酯。1, First, the physiological role of the active metabolite As we all know, the physiological role of vitamin D is (1) the absorption of calcium in the small intestine; (2) renal reabsorption of calcium; (3) dissolution of calcium and phosphorous from bone and (4) bone Calcification. However, recent studies have shown that these effects are not caused by vitamin D but 1,25- (OH) _2D_3. D_3 metabolism in the liver is 25-OH-D_3, which is the main metabolite in the blood, but it is further metabolized by the kidney to 1,25 ~ (OH) _2D_3 or 24,25- (OH) _2D_3 and so on. Metabolism of 24,25-, 23,24- and 25,26- (OH) 2D3,23,25- (OH) 2D3 can also be metabolized to 25-OH- D_3 26,23-lactone. 1,