Ionic movements through light‐sensitive channels of toad rods.
Ionic movements through light‐sensitive channels of toad rods.
复制标题
通过蟾蜍杆光敏通道的离子运动。
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
V. Torre
中科院分区：
文献类型：
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作者：
M. Capovilla;A. Caretta;L. Cervetto;V. Torre
在无Na+细胞外介质的离子操作期间记录离体蟾蜍视网膜中的视杆细胞的电光响应。在外部Ca 2+浓度高于10（-5）M的情况下，仅在外部Na+或Li+存在下观察到电压光响应。当外部Ca ~（2+）降低到10 ~（-6）M以下时，即使在没有Na ~+或Li ~+的情况下，但在存在外部Mg ~（2+）的情况下，也可以检测到正常极性的电压光响应。在存在正常细胞外Ca 2+的情况下，即使在不存在Na+或Li+的情况下，只要向灌注液中加入少量磷酸二酯酶抑制剂（IBMX、RO 20 - 1724、罂粟碱、咖啡因、茶碱），也可观察到超极化光反应。在低Na+ IBMX溶液中获得的响应需要存在毫摩尔量的各种二价阳离子，其中Mn 2+和Ba 2+是最有效的。当外部Ca ~（2+）和Mg ~（2+）的浓度降低到微摩尔量时，观察到去极化光响应。在这些条件下，放射性示踪剂的测量显示42 K+或86 Rb+的光调制流出。光调制的42 K+或86 Rb+流出被2 X 6 mM-外部K+减半，并且当K+升高到10 mM以上时被完全阻断。这些结果表明，通过光敏通道的离子运动由Ca 2+和Mg 2+控制，并且也可能是环核苷酸的细胞内水平。而且，离子通过光敏通道的运动，不遵守独立性原则。
Electrical photoresponses of rods in the isolated toad retina were recorded during ionic manipulations of the Na+‐free extracellular medium. In the presence of a concentration of external Ca2+ above 10(‐5) M, voltage photoresponses were observed only in the presence of external Na+ or Li+. When external Ca2+ was reduced below 10(‐6) M, voltage photoresponses of normal polarity could be detected even in the absence of Na+ or Li+, but in the presence of external Mg2+. In the presence of normal extracellular Ca2+ hyperpolarizing photoresponses were observed even in the absence of Na+ or Li+, provided small amounts of phosphodiesterase inhibitors (IBMX, RO 20‐1724, papaverine, caffeine, theophylline) were added to the perfusate. Responses obtained in low‐Na+ IBMX solutions required the presence of millimolar amounts of a variety of divalent cations, among which Mn2+ and Ba2+ were the most effective. When the concentration of both external Ca2+ and Mg2+ was reduced to micromolar amounts, depolarizing photoresponses were observed. In these conditions measurements with radioactive tracers showed a light‐modulated efflux of 42K+ or 86Rb+. The light‐modulated 42K+ or 86Rb+ efflux was halved by 2 X 6 mM‐external K+ and was completely blocked when K+ was raised above 10 mM. These results show that ionic movements through light‐sensitive channels are controlled by Ca2+ and Mg2+ and possibly also be the intracellular level of cyclic nucleotides. Moreover, the movement of ions through the light‐sensitive channel, does not obey the independence principle.