Ebeling P R, Yergey A L, Vieira N E, Burritt M F, O'Fallon W M, Kumar R, Riggs B L
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905.
Calcif Tissue Int. 1994 Nov;55(5):330-4. doi: 10.1007/BF00299309.
Recent reports of increases in serum 1,25-dihydroxyvitamin D [1,25(OH2)D] concentration with aging despite no changes or decreases in calcium absorption suggest that elderly women have intestinal resistance to vitamin D action. Thus, in 15 young adult (30 +/- 1 year) and 15 elderly (74 +/- 1 year) women (mean +/- SE), we assessed the responsiveness of intestinal calcium absorption to increases in circulating 1,25(OH)2D induced by 4 days of an experimental diet (150 mg calcium and 1600 mg phosphorus daily). True fractional calcium absorption (FCA) (44Ca mixed with food and 42Ca given intravenously, then their ratio in urine measured by mass spectrometry) was determined. Baseline serum intact parathyroid hormone (PTH) concentration was higher in the older women (P = 0.01) whereas serum 1,25(OH)2D concentration and true FCA were similar. In both groups, serum 1,25(OH)2D concentrations increased (P < 0.002) on the experimental diet. After 4 days on the diet, serum 1,25(OH)2D increased over baseline by 30.5 and 35.6% and, despite these increases, true FCA was 40 +/- 3 versus 40 +/- 4%/24 hours (NS between groups) in the young and elderly women, respectively. These data suggest that either elderly women have normal intestinal responsiveness to vitamin D or that the resistance to it is too mild to be detected by these methods.
近期报告显示，尽管钙吸收无变化或有所下降，但血清1,25 - 二羟基维生素D[1,25(OH)₂D]浓度会随衰老而升高，这表明老年女性肠道对维生素D作用存在抵抗。因此，我们选取了15名年轻成年女性（30±1岁）和15名老年女性（74±1岁）（均值±标准误），通过一种实验性饮食（每日150毫克钙和1600毫克磷）4天来评估肠道钙吸收对循环中1,25(OH)₂D升高的反应性。测定了真实的钙吸收分数（FCA）（将⁴⁴Ca与食物混合，静脉注射⁴²Ca，然后通过质谱法测定尿液中它们的比例）。老年女性的基线血清完整甲状旁腺激素（PTH）浓度较高（P = 0.01），而血清1,25(OH)₂D浓度和真实FCA相似。两组在实验性饮食期间，血清1,25(OH)₂D浓度均升高（P < 0.002）。饮食4天后，血清1,25(OH)₂D较基线分别升高了30.5%和35.6%，尽管有这些升高，但年轻和老年女性的真实FCA分别为40±3%/24小时和40±4%/24小时（组间无显著差异）。这些数据表明，要么老年女性肠道对维生素D有正常反应性，要么对其的抵抗过于轻微，无法通过这些方法检测到。
