Masuyama R, Kajita Y, Odachi J, Uehara M, Shigematsu T, Suzuki K, Goto S
Department of Nutritional Science, Tokyo University of Agriculture, Tokyo, Japan.
Am J Nephrol. 2000 Nov-Dec;20(6):491-5. doi: 10.1159/000046206.
Dietary intake of high levels of phosphorus is known to increase serum levels of parathyroid hormone (PTH); however, how this increased serum PTH affects the action of PTH in major target tissues, particularly by kidney, remains unknown. In the present study, we therefore undertook to clarify this point in intact animals fed a high-P diet by examining various parameters of PTH action. Twelve weanling Wistar male rats were assigned randomly to two groups: a control group with dietary Ca:P = 1:1 and a high-P group (Ca:P = 1:3) fed the standard AIN-76 diet supplemented with P (0.5 and 1.5 g/100 g of diet). After 3 weeks of feeding, in the high-P diet group, we observed that serum Ca was lowered, without a difference in serum P, when compared to the control group. Excretion of urinary cAMP, an index of renal PTH action, was also decreased, with higher excretion of urinary P in those rats fed the high-P diet. In agreement with the decreased cAMP excretion, a clear reduction in PTH/PTH-related protein (PTHrP) receptor gene expression as estimated by Northern blotting was observed in the kidney, despite increased levels of serum PTH. Thus, the present study indicated that a high-P diet reduces PTH action in the kidney, though the serum PTH is increased.
已知高磷饮食摄入会增加血清甲状旁腺激素（PTH）水平；然而，这种血清PTH升高如何影响PTH在主要靶组织（尤其是肾脏）中的作用仍不清楚。因此，在本研究中，我们通过检测PTH作用的各种参数，试图在喂食高磷饮食的完整动物中阐明这一点。将12只断乳的Wistar雄性大鼠随机分为两组：对照组饮食中钙磷比为1:1，高磷组（钙磷比为1:3）喂食补充了磷（0.5和1.5 g/100 g饮食）的标准AIN-76饮食。喂食3周后，与对照组相比，高磷饮食组血清钙降低，血清磷无差异。作为肾脏PTH作用指标的尿cAMP排泄也减少，喂食高磷饮食的大鼠尿磷排泄更高。与cAMP排泄减少一致，尽管血清PTH水平升高，但通过Northern印迹法估计，肾脏中PTH/甲状旁腺激素相关蛋白（PTHrP）受体基因表达明显降低。因此，本研究表明，尽管血清PTH升高，但高磷饮食会降低肾脏中的PTH作用。
