Cuche J L, Ott C E, Marchand G R, Diaz-Buxo J A, Knox F G
Am J Physiol. 1976 Mar;230(3):790-6. doi: 10.1152/ajplegacy.1976.230.3.790.
The intrarenal role of plasma ionized calcium (Ca), on fractional phosphate excretion (FE PO4) was investigated in dogs with control of parathyroid hormone (PTH). In series 1, acute thyroparathyroidectomy was immediately followed by a constant infusion of bovine PTH (0.01 U/kg per min). Subsequent calcium chloride infusions increased Cai in plasma phosphate and decreased in the percentage of ultrafiltrable phosphate. A 20% increase in Cai significantly increased FE PO4 by +3.82 +/- 0.97% (P less than 0.01) when infused intravenously and by +2.62 +/- 1.06% (P less than 0.05) when infused in the renal artery. In contrast, a 75% increase in Cai did not significantly change FE PO4. In series 2, dogs were thyroparathyroidectomized 18 h before experiments, and no PTH infusion was initiated. A bolus of bovine PTH (30 U/kg) increased FE PO4 + 8.9 +/- 0.9% (P less than 0.001) in hypocalcemic dogs, +19.1 +/- 4.4% (P less than 0.001) in normolcalcemic dogs, and +15.5 +/- 1.5% (P less than 0.001) in hypercalcemic dogs. We conclude that increases in plasma calcium potentiate the phosphaturic effect of PTH. This potentiating effect is attenuated in marked hypercalcemia by superimposed hemodynamic and/or metabolic changes.
在甲状旁腺激素（PTH）得到控制的犬类中，研究了血浆离子钙（Ca）对磷排泄分数（FE PO4）的肾内作用。在系列1中，急性甲状腺甲状旁腺切除术后立即持续输注牛PTH（0.01 U/kg每分钟）。随后输注氯化钙可使血浆磷酸盐中的离子钙增加，超滤磷酸盐百分比降低。当静脉输注时，离子钙增加20%可使FE PO4显著增加+3.82±0.97%（P<0.01），当通过肾动脉输注时增加+2.62±1.06%（P<0.05）。相比之下，离子钙增加75%并未显著改变FE PO4。在系列2中，犬类在实验前18小时进行甲状腺甲状旁腺切除术，且未开始输注PTH。推注牛PTH（30 U/kg）使低钙血症犬的FE PO4增加+8.9±0.9%（P<0.001），正常钙血症犬增加+19.1±4.4%（P<0.001），高钙血症犬增加+15.5±1.5%（P<0.001）。我们得出结论，血浆钙的增加会增强PTH的排磷作用。在明显的高钙血症中，这种增强作用会因叠加的血流动力学和/或代谢变化而减弱。
