Cholinergic modulation of apical Na+ channels in turtle colon: analysis of CDPC-induced fluctuations.
Cholinergic modulation of apical Na+ channels in turtle colon: analysis of CDPC-induced fluctuations.
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龟结肠顶端 Na 通道的胆碱能调节：CDPC 诱导的波动分析。
DOI：
10.1152/ajpcell.1990.259.4.c668
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Dawson,DC
中科院分区：
文献类型：
--
作者：
Wilkinson,DJ;Dawson,DC
用电流波动分析法研究了毒蕈碱抑制主动Na+吸收过程中顶端Na+通道的特性。使用可逆Na+通道阻断剂6-氯-3，5-二氨基吡嗪-2-甲酰胺（CDPC）诱导短路电流（I（sc））的波动。的CDPC诱导的波动的功率密度谱表现出明显可辨的洛伦兹分量，其特征在于由一个角落频率是线性相关的CDPC浓度在20和100 μ M之间。CDPC阻断反应的开（k ′ on）和关（k（off））速率系数为k ′ on = 11.1 +/-0.8rad·s-1·μ M-1和k（off）= 744 +/-53rad/s，微观抑制常数为67 μ M（n = 11）。在用5 μ M丝氨酸卡巴胆碱抑制Isc后，CDPC阻断动力学没有显著差异。根据40 μ M CDPC诱导的波动估计单通道Na+电流（iNa）和开放和阻断的Na+通道密度（N（ob））。在对照条件下，iNa为0.43 +/- 0.05 pA，N（ob）为251 +/- 42 × 10（6）/cm 2（n = 10）。在暴露于2-10 μ M的丝氨酸氨甲酰胆碱60 min后，Na+电流和N（ob）减少约50%，但iNa无显著变化。这些结果表明，毒蕈碱抑制产电Na+吸收与顶端膜中开放Na+通道的数量减少有关。他们还表明，这种下调的运输涉及协调减少顶端和基底侧膜电导。
Current fluctuation analysis was used to investigate the properties of apical Na+ channels during muscarinic inhibition of active Na+ absorption. A reversible Na+ channel blocker, 6-chloro-3,5-diaminopyrazine-2-carboxamide (CDPC), was used to induce fluctuations in the short-circuit current (I(sc)). Power density spectra of the CDPC-induced fluctuations exhibited a clearly discernible Lorentzian component, characterized by a corner frequency that was linearly related to CDPC concentration between 20 and 100 microM. The on (k'on) and off (k(off)) rate coefficients for the CDPC blocking reaction were k'on = 11.1 +/- 0.8 rad.s-1.microM-1 and k(off) = 744 +/- 53 rad/s, and the microscopic inhibition constant was 67 microM (n = 11). CDPC blocking kinetics were not significantly different after inhibition of Isc by 5 microM serosal carbachol. Single-channel Na+ current (iNa) and the density of open and blocked Na+ channels (N(ob)) were estimated from the fluctuations induced by 40 microM CDPC. Under control conditions, iNa was 0.43 +/- 0.05 pA and N(ob) was 251 +/- 42 X 10(6)/cm2 (n = 10). After exposure to serosal carbachol (2-10 microM) for 60 min, Na+ current and N(ob) were reduced by approximately 50%, but iNa was not changed significantly. These results indicate that muscarinic inhibition of electrogenic Na+ absorption was associated with a reduction in the number of open Na+ channels in the apical membrane. They also suggest that this downregulation of transport involved a coordinated decrease in both apical and basolateral membrane conductances.