Zhou X, Xia S L, Wingo C S
Division of Nephrology, Hypertension, and Transplantation, University of Florida, and Department of Veterans Affairs Medical Center, Gainesville 32608-1197, USA.
J Am Soc Nephrol. 1998 Dec;9(12):2194-202. doi: 10.1681/ASN.V9122194.
The rabbit cortical collecting duct (CCD) exhibits the capacity for active chloride absorption when basolateral Na-K-ATPase is inhibited by ouabain. The present studies examine the contribution of H,K-ATPase to this ouabain-insensitive Cl absorption and to related ion fluxes. Rabbits were fed a KCl-rich diet with no measurable Na for 4 to 13 d before isolation of the CCD for microperfusion. Application of peritubular ouabain (0.1 mM) significantly increased (P < 0.001) net luminal absorptive chloride flux (J(N)Cl) without an effect on lumen-to-bath isotopic 36Cl flux (J(lb)Cl). The H,K-ATPase inhibitor Sch 28080 (1 to 10 microM) abolished ouabain-insensitive J(N)Cl, but transepithelial voltage (V(T)) was not significantly affected. The contribution of H,K-ATPase activity on active Cl flux (J(A)Cl) and passive Cl flux (J(P)Cl) was also assessed. Ouabain significantly increased J(A)Cl and Sch 28080 inhibited J(A)Cl, but J(P)Cl was not affected by Sch 28080. To assess the contribution of changes in net bicarbonate flux (JtCO2) to changes in J(N)Cl, JtCO2 was measured under identical conditions as for J(N)Cl. Ouabain significantly increased JtCO2, and this ouabain-insensitive bicarbonate flux was inhibited by Sch 28080 without significantly affecting V(T). To assess the possibility that the CCD may possess mechanisms for neutral salt absorption, lumen-to-bath 86Rb efflux (K(Rb)), and 22Na efflux (K(Na)) were also measured. Ouabain significantly increased K(Rb), and Sch 28080 inhibited this ouabain-insensitive K(Rb). Furthermore, Sch 28080 and A80915a (a structurally distinct H,K-ATPase inhibitor) significantly inhibited K(Na) in the presence of 1 mM luminal amiloride. These observations suggest that, in addition to potassium, sodium can be transported via the H,K-ATPase. Although the CCD contains more than one cell population, the data could be fitted very well to the function of the B-type intercalated cell. A cell model is proposed for the hypothesis that ouabain-insensitive chloride absorption is mediated by the parallel operation of an apical H,K-ATPase with an apical Cl-HCO3 exchanger and that the H,K-ATPase can function, under certain conditions, as a mechanism of Na absorption.
当哇巴因抑制基底外侧的钠钾ATP酶时，兔皮质集合管（CCD）具有主动吸收氯离子的能力。本研究探讨了氢钾ATP酶对这种哇巴因不敏感的氯离子吸收及相关离子转运的作用。在分离CCD进行微灌注前，给兔喂食富含氯化钾且无可测钠的饮食4至13天。管周应用哇巴因（0.1 mM）显著增加（P < 0.001）了管腔净吸收性氯离子通量（J(N)Cl），而对管腔至浴液的同位素36Cl通量（J(lb)Cl）无影响。氢钾ATP酶抑制剂Sch 28080（1至10 microM）消除了哇巴因不敏感的J(N)Cl，但跨上皮电压（V(T)）未受显著影响。还评估了氢钾ATP酶活性对主动氯离子通量（J(A)Cl）和被动氯离子通量（J(P)Cl）的作用。哇巴因显著增加J(A)Cl，Sch 28080抑制J(A)Cl，但J(P)Cl不受Sch 28080影响。为评估净碳酸氢盐通量（JtCO2）变化对J(N)Cl变化的作用，在与J(N)Cl相同的条件下测量JtCO2。哇巴因显著增加JtCO2，且这种哇巴因不敏感的碳酸氢盐通量被Sch 28080抑制，而对V(T)无显著影响。为评估CCD可能具有中性盐吸收机制的可能性，还测量了管腔至浴液的86Rb外流（K(Rb)）和22Na外流（K(Na)）。哇巴因显著增加K(Rb)，Sch 28080抑制这种哇巴因不敏感的K(Rb)。此外，在管腔存在1 mM阿米洛利的情况下，Sch 28080和A80915a（一种结构不同的氢钾ATP酶抑制剂）显著抑制K(Na)。这些观察结果表明，除了钾之外，钠也可通过氢钾ATP酶转运。尽管CCD包含不止一种细胞群体，但数据能很好地拟合B型闰细胞的功能。提出了一个细胞模型，用于解释哇巴因不敏感的氯离子吸收是由顶端氢钾ATP酶与顶端氯-碳酸氢根交换体并行运作介导的这一假说，并且氢钾ATP酶在某些条件下可作为钠吸收的一种机制发挥作用。
