Bleached pigment activates transduction in salamander cones.
Bleached pigment activates transduction in salamander cones.
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DOI：
10.1085/jgp.106.3.543
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发表时间：
1995-09
期刊：
影响因子：
--
通讯作者：
Fain GL
中科院分区：
文献类型：
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作者：
Cornwall MC;Matthews HR;Crouch RK;Fain GL
我们使用吸力电极记录以及快速进入 0.5 mM IBMX 溶液来研究蝾螈 Ambystoma tigrinum 孤立视锥细胞中色素漂白所产生的鸟苷酸环化酶速度的变化。背景和漂白剂都会加速进入 IBMX 过程中电流增加的时间进程。我们将此解释为鸟苷酸环化酶的速度在背景光下或漂白后增加的证据。我们的结果表明，环化酶速度随着颜料漂白百分比的增加而几乎线性增加，但随着背景强度的增加而非线性（并且可能饱和）。在视锥细胞中（如之前在视杆细胞中所证明的那样），光激活色素和漂白色素似乎对转导级联有一些不同的影响。去除光后，漂白对环化酶速率的影响至少维持 15-20 分钟，比漂白后循环电流和稳定在隔离锥体中的灵敏度所需的时间长得多。用含有 11-顺式视黄醛的脂质体治疗可以完全逆转对环化酶速率的影响。 β-紫罗兰酮也可以部分逆转漂白效果，β-紫罗兰酮是发色团 11-顺式-视黄醛的类似物，不与视蛋白形成共价连接。用β-紫罗兰酮灌注漂白的锥体会导致循环电流和灵敏度快速增加，当去除β-紫罗兰酮时，这种情况会迅速逆转。用β-紫罗兰酮灌注还可以部分逆转漂白剂引起的环化酶速度加速。我们得出的结论是，漂白可能通过类似于杆状细胞的机制，对视锥细胞中的转导级联产生“等效背景”激发。
We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current increase during steps into IBMX. We interpret this as evidence that the velocity of the guanylyl cyclase is increased in background light or after bleaching. Our results indicate that cyclase velocity increases nearly linearly with increasing percent pigment bleached but nonlinearly (and may saturate) with increasing back-ground intensity. In cones (as previously demonstrated for rods), light-activated pigment and bleached pigment appear to have somewhat different effects on the transduction cascade. The effect of bleaching on cyclase rate is maintained for at least 15-20 min after the light is removed, much longer than is required after a bleach for circulating current and sensitivity to stabilize in an isolated cone. The effect on the cyclase rate can be completely reversed by treatment with liposomes containing 11-cis retinal. The effects of bleaching can also be partially reversed by beta-ionone, an analogue of the chromophore 11- cis-retinal which does not form a covalent attachment to opsin. Perfusion of a bleached cone with beta-ionone produces a rapid increase in circulating current and sensitivity, which rapidly reverses when the beta-ionone is removed. Perfusion with beta-ionone also causes a partial reversal of the bleach-induced acceleration of cyclase velocity. We conclude that bleaching produces an "equivalent background" excitation of the transduction cascade in cones, perhaps by a mechanism similar to that in rods.