Na+-dependent H+ efflux from proximal tubule: evidence for reversible Na+-H+ exchange.
Na+-dependent H+ efflux from proximal tubule: evidence for reversible Na+-H+ exchange.
复制标题
Na 依赖性 H 从近端小管流出：可逆 Na -H 交换的证据。
DOI：
10.1152/ajprenal.1981.241.4.f380
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Schwartz,GJ
中科院分区：
文献类型：
--
作者：
Schwartz,GJ
去除Na+或加入哇巴因抑制HCO 3（-）和Na+在兔近端小管的吸收，这一发现提示Na+-H+偶联。然而，抑制Na+转运可能通过减少能量代谢而不是直接抑制Na+-H+交换来减少H+分泌。H+从腔液中消失，这取决于Na+梯度的方向和大小，应该是细胞Na+的函数，独立于细胞代谢。如果细胞Na+被哇巴因增加，H+消失应该增加;当细胞Na+被Na+去除减少时，对于给定的pH差异，较少的H+应该使管腔水平化。从家兔肾脏解剖出浅表早期近曲小管，并在体外用无CO2（-）和HCO 3（-）的溶液（pH 6.45）快速灌注。该浴类似于灌注液，不同之处在于pH为7.4并且含有6 g/dl的白蛋白。H+流出量根据灌注液和收集液之间的pH值差异、流速和灌注液的缓冲能力来计算。当灌注液和浴中存在145 mM Na+时，H+流出量为5.3 +/- 0.4 pmol。cm-1 . s-1，并且当哇巴因加入到浴中时增加了39 +/-16%。用胆碱或Li+替代Na+导致H+流出减少44 +/- 7%。去除管腔有机溶质显着减少H+外流，但是，它仍然增强了哇巴因加入浴。即使在不存在Na+或管腔有机溶质的情况下，也存在大量明显的H+渗漏渗透性。在10 mM Na+培养基中加入10（-4）M阿米洛利，导致H+流出减少34 +/-6%。结果表明，在近端小管中的H+运输介导的，至少部分，由一个可逆的Na+-H+交换驱动的H+和Na+梯度之间的差异。
Removal of Na+ or addition of ouabain inhibits HCO3(-) and Na+ absorption in rabbit proximal tubule, a finding suggestive of Na+-H+ coupling. However, inhibition of Na+ transport might decrease H+ secretion by reducing energy metabolism rather than by inhibiting Na+-H+ exchange directly. H+ disappearance from the luminal fluid, which depends on direction and magnitude of Na+ gradient, should be a function of cell Na+, independent of cellular metabolism. If cell Na+ is increased by ouabain, H+ disappearance should increase; when cell Na+ is reduced by Na+ removal, less H+ should level the lumen for a given pH difference. Superficial early proximal convoluted tubules were dissected from rabbit kidney and perfused rapidly in vitro with CO2(-) and HCO3(-)-free solutions (pH 6.45). The bath resembled perfusate except that the pH was 7.4 and contained 6 g/dl of albumin. H+ efflux was calculated from the difference in pH between perfused and collected fluid, flow rate, and buffer capacity of the perfusate. When 145 mM Na+ was present in perfusate and bath, H+ efflux was 5.3 +/- 0.4 pmol . cm-1 . s-1 and increased by 39 +/- 16% when ouabain was added to the bath. Replacement of Na+ by choline or Li+ caused a 44 +/- 7% decrease in H+ efflux. Removal of luminal organic solutes markedly reduced H+ efflux; however, it was still enhanced by addition of ouabain to the bath. Even in the absence of Na+ or luminal organic solutes, a substantial apparent H+ leak permeability exists. Addition of 10(-4) M amiloride to a 10 mM Na+ medium caused a 34 +/- 6% reduction in H+ efflux. The results indicate that H+ transport in the proximal tubule is mediated, at least in part, by a reversible Na+-H+ exchanger driven by the difference between H+ and Na+ gradients.