Saito K, Hirano K, Kubota M, Tomino Y, Koide H
Department of Medicine, Juntendo University School of Medicine, Tokyo, Japan.
Nephron. 1993;64(4):600-4. doi: 10.1159/000187407.
Parathyroid-hormone-related protein (PTHrP) has significant homology with parathyroid hormone (PTH) in the amino-terminal region. We compared the effects of synthetic human PTHrP [hPTHrP(1-34)] on Na(+)-dependent phosphate transport with those of synthetic human PTH [hPTH(1-34)]. Intravenous administration of hPTHrP(1-34) in parathyroidectomized rats caused hypercalcemia, hypophosphatemia and phosphaturia to the same degree as hPTH(1-34). In kinetic studies using renal brush border membrane vesicles, the apparent Km and Vmax of phosphate transport were identical for the two peptides [hPTHrP(1-34): Km 27.6 +/- 0.8 microM, Vmax 3.78 +/- 0.04 nmol/mg protein, hPTH(1-34): Km 29.6 +/- 0.9 microM, Vmax 3.04 +/- 0.90 nmol/mg protein]. Both hPTHrP(1-34) and hPTH(1-34) at a supramaximal dose were equipotent in eliciting a 12-fold increase in cyclic adenosine 3',5'-monophosphate (cAMP) production in the kidney. These results indicate that, in addition to the similar effect of hPTHrP(1-34) and hPTH(1-34) on serum calcium levels and urinary phosphorus and nephrogenous cAMP excretion in vivo, these two peptides have similar effects of Na(+)-dependent phosphate transport in brush border membrane vesicles in vitro.
甲状旁腺激素相关蛋白（PTHrP）在氨基末端区域与甲状旁腺激素（PTH）具有显著的同源性。我们比较了合成人PTHrP [hPTHrP(1-34)]与合成人PTH [hPTH(1-34)]对钠依赖性磷酸盐转运的影响。在甲状旁腺切除的大鼠中静脉注射hPTHrP(1-34)，导致高钙血症、低磷血症和磷尿症，其程度与hPTH(1-34)相同。在使用肾刷状缘膜囊泡的动力学研究中，两种肽的磷酸盐转运表观Km和Vmax相同 [hPTHrP(1-34)：Km 27.6±0.8微摩尔，Vmax 3.78±0.04纳摩尔/毫克蛋白，hPTH(1-34)：Km 29.6±0.9微摩尔，Vmax 3.04±0.90纳摩尔/毫克蛋白]。hPTHrP(1-34)和hPTH(1-34)在超最大剂量时，在引起肾脏中环磷酸腺苷（cAMP）产生增加12倍方面具有同等效力。这些结果表明，除了hPTHrP(1-34)和hPTH(1-34)在体内对血清钙水平、尿磷和肾源性cAMP排泄具有相似作用外，这两种肽在体外对肾刷状缘膜囊泡中的钠依赖性磷酸盐转运也具有相似作用。
