Vieth R, Fraser D, Kooh S W
J Nutr. 1987 May;117(5):914-8. doi: 10.1093/jn/117.5.914.
We investigated whether dietary factors that are known to increase 1,25-(OH)2-cholecalciferol production can deplete plasma 25-OH-cholecalciferol. Plasma concentration of 25-OH-cholecalciferol, its metabolism in vivo and activities of renal mitochondrial 25-OH-cholecalciferol 1-hydroxylase (1-OHase) and 25-OH-cholecalciferol 24-hydroxylase (24-OHase) were measured in rats fed various amounts of calcium (Ca) and phosphorus (P). All diets contained 5 micrograms (200 IU) cholecalciferol per 100 g. For rats fed the "normal" diet (0.7% Ca and 1.2% P) the mean plasma 25-OH-cholecalciferol level was 11.0 +/- 0.8 nmol/L, and the mean 1-OHase activity was 30 +/- 5 fmol/(mg X min). All rats fed the low Ca (0.014%) diet had 1-OHase activities above 200 fmol/(mg X min) and undetectable plasma 25-OH-cholecalciferol levels (less than 2.5 nmol/L). The chi-square test interrelating plasma 25-OH-cholecalciferol and dietary Ca showed statistical significance (P less than 0.001). The high activity of 1-OHase that resulted from dietary Ca restriction increased utilization of 25-OH-cholecalciferol to the point of causing depletion of this metabolite in the circulation.
我们研究了已知可增加1,25 -（OH）₂ - 胆钙化醇生成的饮食因素是否会消耗血浆25 - OH - 胆钙化醇。在喂食不同钙（Ca）和磷（P）含量的大鼠中，测量了血浆25 - OH - 胆钙化醇的浓度、其体内代谢以及肾线粒体25 - OH - 胆钙化醇1 - 羟化酶（1 - OHase）和25 - OH - 胆钙化醇24 - 羟化酶（24 - OHase）的活性。所有饮食每100克含5微克（200国际单位）胆钙化醇。对于喂食“正常”饮食（0.7% Ca和1.2% P）的大鼠，血浆25 - OH - 胆钙化醇的平均水平为11.0±0.8纳摩尔/升，1 - OHase的平均活性为30±5飞摩尔/（毫克×分钟）。所有喂食低钙（0.014%）饮食的大鼠1 - OHase活性高于200飞摩尔/（毫克×分钟），且血浆25 - OH - 胆钙化醇水平检测不到（低于2.5纳摩尔/升）。将血浆25 - OH - 胆钙化醇与饮食钙相关联的卡方检验显示具有统计学意义（P＜0.001）。饮食钙限制导致的1 - OHase高活性增加了25 - OH - 胆钙化醇的利用，直至导致该代谢物在循环中耗竭。
