Nucleotides have diverse effects on water and electrolyte reabsorption within the distal tubule of the nephron. As the distal tubule is important in control of renal Mg(2+) balance, we determined the effects of ATP on cellular Mg(2+) uptake in this segment. The effects of ATP on immortalized mouse distal convoluted tubule (MDCT) cells were studied by measuring Mg(2+) uptake with fluorescence techniques. The mean basal Mg(2+) uptake rate was 165 +/- 6 nM/s. ATP inhibited basal Mg(2+) uptake and hormone-stimulated Mg(2+) entry by 40%. Both P2X (P2X1-P2X5 subtypes) and P2Y2 receptor subtypes were identified in MDCT cells using differential RT-PCR. Activation of both receptor subtypes with selective agonists increased intracellular Ca(2+) concentration, P2X purinoceptors by ionotropic-gated channels, and P2Y receptors via G protein-mediated intracellular Ca(2+) release. The more relatively selective P2X agonists [beta,gamma-methylene ATP (beta,gamma-Me-ATP) and 2'- and -3'-O-(4-benzoyl-benzoyl)-ATP] inhibited arginine vasopressin (AVP)- and parathyroid hormone (PTH)-mediated Mg(2+) uptake whereas agonists more selective for P2Y purinoceptors (UTP, ADP, and 2-methylthio-ATP) were without effect. Removal of extracellular Ca(2+) diminished beta,gamma-Me-ATP-mediated increase in intracellular Ca(2+) and inhibition of AVP-stimulated Mg(2+) entry. We conclude from this information that ATP inhibited Mg(2+) uptake in MDCT cells through P2X purinoceptors expressed in this distal convoluted tubule cell line.

译文

核苷酸对肾单位远端小管内的水和电解质重吸收有多种影响。由于远端小管在控制肾脏Mg(2) 平衡方面很重要,因此我们确定了ATP对该节段中细胞Mg(2) 摄取的影响。通过荧光技术测量Mg(2) 的摄取,研究了ATP对永生化小鼠远曲小管 (MDCT) 细胞的影响。平均基础Mg(2 +) 摄取速率为165 +/- 6 nM/s。ATP通过40% 抑制基础Mg(2 +) 摄取和激素刺激的Mg(2 +) 进入。使用差异rt-pcr在MDCT细胞中鉴定出P2X (P2X1-P2X5亚型) 和P2Y2受体亚型。选择性激动剂激活两种受体亚型均增加了细胞内Ca(2) 的浓度,离子型门控通道的P2X嘌呤受体以及通过g蛋白介导的细胞内Ca(2) 释放的P2Y受体。比较选择性的P2X激动剂 [β,γ-亚甲基ATP (β,Γ-Me-ATP) 和2 '-和-3'-O-(4-苯甲酰基)-ATP] 抑制精氨酸加压素 (AVP)-和甲状旁腺激素 (PTH) 介导的Mg(2) 摄取,而激动剂对P2Y嘌呤受体更具选择性 (UTP,ADP,和2-甲硫基-atp) 没有作用。去除细胞外Ca(2) 可减少 β,γ-Me-ATP介导的细胞内Ca(2) 的增加,并抑制AVP刺激的Mg(2) 进入。我们从该信息得出结论,ATP通过在该远端曲小管细胞系中表达的P2X嘌呤受体抑制了MDCT细胞中Mg(2) 的摄取。

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