Membrane conductances of principal cells in Malpighian tubules of Aedes aegypti
Membrane conductances of principal cells in Malpighian tubules of Aedes aegypti
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DOI：
10.1016/s0022-1910(02)00057-4
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发表时间：
2002-03-01
影响因子：
2.2
通讯作者：
Masia, R
中科院分区：
文献类型：
--
作者：
Beyenbach, KW;Masia, R
用双电极电压钳(TEVC)方法研究了黄热病蚊马氏管优势细胞--主细胞的传导转运途径。在对照条件下，49个主细胞的基底膜电压(V-bl)为-85.1 mV。通过测量输入电阻R-pc和膜的分数电阻，得到基侧膜(g(Bl)=1.48mus)和根尖膜(g(A)=3.13mus)的电导估计值。被钡阻断的K+通道占g(Bl)的0.94mus。对转移数的估计得出基侧膜Na+电导为0.24mus，剩余0.30mus(20%)的g(Bl)。促分泌剂db-cAMP(0.1 mM)可显著去极化Vb(1)至-65.0 mV，并显著增加g，从1.48 mus增加至2.47 mus。这种增加被阿米洛利(1 MM)阻断，阿米洛利是一种已知的上皮Na+转运阻断剂。二硝基苯酚抑制代谢可使Vb1去极化至-9.7mV，Rp显著增加，从391.6 kq增至2612.5 kq。氰化物也得到了类似的结果，但目前尚不清楚RPC的大幅增加是否源于上皮细胞的解偶联和/或基底侧膜和根尖膜传导运输通路的关闭。我们的结果表明，主细胞的顶膜的传导性是基侧膜的两倍以上。部分离子电导提示跨上皮膜Na+分泌的限速步骤。(C)2002爱思唯尔科学有限公司。保留所有权利。
Two-electrode voltage clamp (TEVC) methods were used to explore conductive transport pathways in principal cells, the dominant cell type in Malpighian tubules of the yellow fever mosquito. The basolateral membrane of principal cells had a voltage (V-bl) Of -85.1 mV in 49 principal cells under control conditions. Measures of the input resistance R-pc together with membrane fractional resistance yielded estimates of the conductance of the basolateral membrane (g(bl) = 1.48 muS) and the apical membrane (g(a) = 3.13 muS). K+ channels blocked by barium accounted for 0.94 muS of g(bl). Estimates of transference numbers yielded the basolateral membrane Na+ conductance of 0.24 muS, leaving 0.30 muS (20%) Of g(bl) unaccounted. The secretagogue db-cAMP (0.1 mM), a known activator of the basolateral membrane Na+ conductance, significantly depolarized Vb(1) to -65.0 mV and significantly increased g, from 1.48 muS to 2.47 muS. The increase was blocked with amiloride (1 mM), a known blocker of epithelial Na+ transport. The inhibition of metabolism with di-nitrophenol significantly depolarized Vb1 to -9.7 mV and significantly increased RP, from 391.6 kQ to 2612.5 kQ. Similar results were obtained with cyanide, but it remains unclear whether the large increases in Rpc stem from the uncoupling of epithelial cells and/or the shutdown of conductive transport pathways in basolateral and apical membranes. Our results indicate that the apical membrane of principal cells is more than twice as conductive as the basolateral membrane. Partial ionic conductances suggest the rate-limiting step for transepithelial Na+ secretion at the basolateral membrane. (C) 2002 Elsevier Science Ltd. All rights reserved.