ON THE MECHANISM OF PARATHYROID-HORMONE STIMULATION OF CALCIUM-UPTAKE BY MOUSE DISTAL CONVOLUTED TUBULE CELLS
ON THE MECHANISM OF PARATHYROID-HORMONE STIMULATION OF CALCIUM-UPTAKE BY MOUSE DISTAL CONVOLUTED TUBULE CELLS
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DOI：
10.1172/jci115947
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发表时间：
1992-09-01
影响因子：
15.9
通讯作者：
FRIEDMAN, PA
中科院分区：
文献类型：
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作者：
GESEK, FA;FRIEDMAN, PA
甲状旁腺激素刺激肾远曲小管的跨细胞Ca2+吸收。在永生化小鼠远曲小管细胞上测定PTH对膜电压的影响、电压变化的离子基础以及电压与钙进入的关系。PTH （10(-8) M）显著增加Ca-45（2+）的摄取，从基础水平2.81 +/- 0.16到3.88 +/- 0.19 nmol min-1 mg蛋白-1。pth诱导的Ca-45（2+）摄取被二氢吡啶拮抗剂硝苯地平（10(-5)M）所消除。甲状旁腺素不影响Na-22+的摄取。在加载fura-2的细胞中测量细胞内钙活性（[Ca2+]i）。对照[Ca2+]i平均为112 +/- 21 nM。PTH在10（11）至10(-7)M范围内增加[Ca2+]i，在10(-8)M PTH时达到326 +/- 31 nM的最大刺激。用电位敏感染料DiO6(3)测得静息膜电压平均为-71 +/- 2 mV。PTH超极化细胞为19 +/- 4 mV。氯离子通道阻滞剂NPPB阻止了pth诱导的超极化。用荧光染料SPQ测定PTH降低，NPPB增加细胞内氯化物。通过测量I-125-的流出速率来估计氯离子的渗透率。甲状旁腺素增加了I-125的外排，这种作用被NPPB阻断。K+/缬霉素箝位电压；通过还原胞外氯离子使膜电压去极化；或添加NPPB阻止甲状旁腺激素诱导的钙摄取。综上所述，甲状旁腺激素增加远曲小管细胞的氯离子电导，导致细胞内氯离子活性降低，膜超极化，并增加钙通过二氢吡啶敏感钙通道进入。
PTH stimulates transcellular Ca2+ absorption in renal distal convoluted tubules. The effect of PTH on membrane voltage, the ionic basis of the change in voltage, and the relations between voltage and calcium entry were determined on immortalized mouse distal convoluted tubule cells. PTH (10(-8) M) significantly increased Ca-45(2+) uptake from basal levels of 2.81 +/- 0.16 to 3.88 +/- 0.19 nmol min-1 mg protein-1. PTH-induced Ca-45(2+) uptake was abolished by the dihydropyridine antagonist, nifedipine (10(-5) M). PTH did not affect Na-22+ uptake. Intracellular calcium activity ([Ca2+]i) was measured in cells loaded with fura-2. Control [Ca2+]i averaged 112 +/- 21 nM. PTH increased [Ca2+]i over the range of 10(11) to 10(-7) M. Maximal stimulation to 326 +/- 31 nM was achieved at 10(-8) M PTH. Resting membrane voltage measured with the potential sensitive dye DiO6(3) averaged -71 +/- 2 mV. PTH hyperpolarized cells by 19 +/- 4 mV. The chloride-channel blocker NPPB prevented PTH-induced hyperpolarization. PTH decreased and NPPB increased intracellular chloride, measured with the fluorescent dye SPQ. Chloride permeability was estimated by measuring the rate of I-125- efflux. PTH increased I-125- efflux and this effect was blocked by NPPB. Clamping voltage with K+/valinomycin; depolarizing membrane voltage by reducing extracellular chloride; or addition of NPPB prevented PTH-induced calcium uptake. In conclusion, PTH increases chloride conductance in distal convoluted tubule cells leading to decreased intracellular chloride activity, membrane hyperpolarization, and increased calcium entry through dihydropyridine-sensitive calcium channels.