Ca2+ dependence of flow-stimulated K secretion in the mammalian cortical collecting duct
Ca2+ dependence of flow-stimulated K secretion in the mammalian cortical collecting duct
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DOI：
10.1152/ajprenal.00057.2007
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发表时间：
2007-07-01
影响因子：
4.2
通讯作者：
Satlin, Lisa M.
中科院分区：
文献类型：
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作者：
Liu, Wen;Morimoto, Tetsuji;Satlin, Lisa M.
顶端低电导SK通道和高电导钙激活BK通道存在于包括皮质集合管在内的远端肾单位。流刺激性净K分泌(JK)是1)被BK而不是SK通道的抑制剂伊贝里奥毒素阻断，以及2)与[Ca~(2+)](I)升高有关，这使我们得出结论，BK通道介导了流刺激性J(K)。为了研究钙离子依赖和钙离子来源对流动刺激的JK的影响，测定了慢(类似于1)和快(类似于5nL())下的J(K)和净钠吸收(J(Na))。Min(-1)(.)在无钙离子存在的情况下，或在用BAPTA-AM预处理细胞内钙离子，2-氨基乙氧基二苯基硼酸酯(2-APB)，以抑制肌醇1，4，5-三磷酸(IP3)受体或thapsigargin耗尽内存储器后，微灌流兔CCDs的流速。这些治疗不影响流刺激的JNA(Morimoto等人)。Am J Physiol Renal Physiol 291：F663-F669,2006)，抑制流动刺激的JK。[Ca~(2+)]的增加(I)刺激胞吐。为了检测FLOW是否诱导预先形成的BK通道胞外插入到根尖膜内，用10u M秋水仙碱(Col)破坏微管功能或用5mU g/ml灯盏花素-A(BFA)抑制通道从细胞内池到质膜的输送。这两种药物都抑制流刺激的JK，但不抑制JNA(Morimoto等人)。Am J Physiol Renal Physiol 291：F663-F669,2006)，尽管Col而不是BFA也阻断了流动诱导的[Ca~(2+)]i瞬变。因此，我们推测，BK通道介导的、流刺激的JK需要增加[Ca~(2+)](I)，部分原因是腔内Ca~(2+)进入和ER Ca~(2+)释放、微管完整性和预先形成的通道向顶膜的胞外插入。
Apical low-conductance SK and high-conductance Ca2+-activated BK channels are present in distal nephron, including the cortical collecting duct (CCD). Flow-stimulated net K secretion (JK) in the CCD is 1) blocked by iberiotoxin, an inhibitor of BK but not SK channels, and 2) associated with an increase in [Ca2+](i), leading us to conclude that BK channels mediate flow-stimulated J(K). To examine the Ca2+ dependence and sources of Ca2+ contributing to flow-stimulated JK, J(K) and net Na absorption (J(Na)) were measured at slow (similar to 1) and fast (similar to 5 nl (.) min(-1) (.) mm(-1)) flow rates in rabbit CCDs microperfused in the absence of luminal Ca2+ or after pretreatment with BAPTA-AM to chelate intracellular Ca2+, 2-aminoethoxydiphenyl borate (2-APB), to inhibit the inositol 1,4,5-trisphosphate (IP3) receptor or thapsigargin to deplete internal stores. These treatments, which do not affect flow-stimulated JNa (Morimoto et al. Am J Physiol Renal Physiol 291: F663-F669, 2006), inhibited flow-stimulated JK. Increases in [Ca2+](i) stimulate exocytosis. To test whether flow induces exocytic insertion of preformed BK channels into the apical membrane, CCDs were pretreated with 10 mu M colchicine (COL) to disrupt microtubule function or 5 mu g/ml brefeldin-A (BFA) to inhibit delivery of channels from the intracellular pool to the plasma membrane. Both agents inhibited flow-stimulated JK but not JNa (Morimoto et al. Am J Physiol Renal Physiol 291: F663 - F669, 2006), although COL but not BFA also blocked the flow-induced [Ca2+] i transient. We thus speculate that BK channel-mediated, flow-stimulated JK requires an increase in [Ca2+](i) due, in part, to luminal Ca2+ entry and ER Ca2+ release, microtubule integrity, and exocytic insertion of preformed channels into the apical membrane.