Boyle I T, Gray R W, DeLuca H F
Proc Natl Acad Sci U S A. 1971 Sep;68(9):2131-4. doi: 10.1073/pnas.68.9.2131.
Tritiated 1,25-dihydroxycholecalciferol accumulates in several tissues, to an extent that varies with dietary calcium content, 12 hr after the administration of 325 pmoles of tritiated 25-hydroxycholecalciferol to rats. As the dietary and serum calcium concentrations increase, the amount of 1,25-dihydroxycholecalciferol is diminished and the concentration of 21,25-dihydroxycholecalciferol increases. This correlation is especially evident in rats given vitamin D(3). In vitamin D-deficient rats, the repression of 1,25-dihydroxycholecalciferol formation occurs with a diet containing 3% calcium and 20% lactose. The results suggest that the production of 1,25-dihydroxycholecalciferol, believed to be the metabolically active form of vitamin D in the intestine, is responsible for the adaptation of calcium absorption to low dietary concentrations of calcium.
给大鼠注射325皮摩尔的氚标记25-羟基胆钙化醇12小时后，氚标记的1,25-二羟基胆钙化醇会在多个组织中蓄积，其蓄积程度会因饮食中钙含量的不同而有所变化。随着饮食和血清钙浓度的升高，1,25-二羟基胆钙化醇的量会减少，而21,25-二羟基胆钙化醇的浓度会增加。这种相关性在给予维生素D(3)的大鼠中尤为明显。在维生素D缺乏的大鼠中，当饮食中含有3%的钙和20%的乳糖时，1,25-二羟基胆钙化醇的形成会受到抑制。结果表明，1,25-二羟基胆钙化醇被认为是维生素D在肠道中的代谢活性形式，它的产生负责使钙吸收适应低饮食钙浓度。
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