Yamada H, Seki G, Taniguchi S, Uwatoko S, Nosaka K, Suzuki K, Kurokawa K
First Department of Internal Medicine, Tokyo University School of Medicine, Japan.
Am J Physiol. 1996 Nov;271(5 Pt 2):F1068-76. doi: 10.1152/ajprenal.1996.271.5.F1068.
Roles of Ca2+ and protein kinase C (PKC) in the regulation of acid/base transport in isolated rabbit proximal tubules were investigated by measuring cytosolic Ca2+ concentrations ([Ca2+]i) and cell pH (pHi) with fluorescent probes. Ionomycin (0.2 microM) increased [Ca2+]i by approximately 200 nM but did not affect the basolateral Na(+)-HCO3- cotransporter. However, the apical Na+/H+ exchanger was inhibited by 50% by ionomycin, and this inhibition was abolished either by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, an intracellular Ca2+ chelator, or by KN-62, an inhibitor of calcium-calmodulin-dependent protein kinase II (CaM kinase II). On the other hand, phorbol 12-myristate 13-acetate (PMA, 0.5 microM) did not affect the apical Na+/H+ exchanger but did stimulate the basolateral Na(+)-HCO3- cotransporter by 60-80%, and this stimulation was prevented by calphostin C, an inhibitor of PKC. Consistent with the cotransporter stimulation, PMA decreased steady-state pHi in the presence of CO2/ HCO3-. These results indicate that 1) the acute increase in [Ca2+]i within physiological ranges inhibits the apical Na+/H+ exchanger, probably through mediation of CaM kinase II; and 2) the short-term PKC activation stimulates the basolateral Na(+)-HCO3- cotransporter.
通过使用荧光探针测量胞质钙离子浓度（[Ca2+]i）和细胞内pH值（pHi），研究了钙离子（Ca2+）和蛋白激酶C（PKC）在离体兔近端小管酸碱转运调节中的作用。离子霉素（0.2微摩尔）使[Ca2+]i增加约200纳摩尔，但不影响基底外侧钠-碳酸氢根协同转运体。然而，离子霉素使顶端钠/氢交换体活性抑制50%，而这种抑制作用可被细胞内钙离子螯合剂1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸或钙调蛋白依赖性蛋白激酶II（CaM激酶II）抑制剂KN-62消除。另一方面，佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA，0.5微摩尔）不影响顶端钠/氢交换体，但使基底外侧钠-碳酸氢根协同转运体活性增强60%-80%，这种增强作用可被PKC抑制剂钙泊三醇C阻止。与协同转运体活性增强一致，在有二氧化碳/碳酸氢根存在的情况下，PMA降低了稳态pHi。这些结果表明：1）生理范围内[Ca2+]i的急性增加可能通过CaM激酶II的介导抑制顶端钠/氢交换体；2）短期PKC激活刺激基底外侧钠-碳酸氢根协同转运体。
