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质子对光感受器膜片中3',5'-环鸟苷酸激活电流的影响。

The effects of protons on 3',5'-cGMP-activated currents in photoreceptor patches.

作者信息

Tanaka J C

机构信息

Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104-6089.

出版信息

Biophys J. 1993 Dec;65(6):2517-23. doi: 10.1016/S0006-3495(93)81294-3.

Abstract

Macroscopic 3',5'-guanine cyclic monophosphate (cGMP)-activated currents from photoreceptor outer segment membranes were examined as the pH on the cytoplasmic face of inside/out patches was reduced. In the absence of divalent cations, protons reduced the current in both directions without affecting the shape of the current-voltage relation consistent with a voltage-independent block. When Ca2+ was added to the bath, increasing the [H+] relieved the Ca2+ block and eliminated the Ca(2+)-induced reversal potential shifts seen at pH 7.4. These results suggest that protons alter Na+/Ca2+ permeability of the channel and relieve Ca2+ block of the sodium transport.

摘要

当从内向外膜片的胞质面的pH降低时,检测了来自光感受器外段膜的宏观3',5'-环磷酸鸟苷(cGMP)激活电流。在没有二价阳离子的情况下,质子在两个方向上都降低了电流,而不影响电流-电压关系的形状,这与电压无关的阻断一致。当向浴槽中加入Ca2+时,增加[H+]可缓解Ca2+阻断,并消除在pH 7.4时观察到的Ca(2+)诱导的反转电位偏移。这些结果表明,质子改变了通道的Na+/Ca2+通透性,并缓解了钠转运的Ca2+阻断。

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