Effects of cyclic GMP on the kinetics of the photocurrent in rods and in detached rod outer segments.
Effects of cyclic GMP on the kinetics of the photocurrent in rods and in detached rod outer segments.
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DOI：
10.1085/jgp.90.4.527
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发表时间：
1987-10
期刊：
影响因子：
--
通讯作者：
Korenbrot JI
中科院分区：
文献类型：
--
作者：
Hestrin S;Korenbrot JI
我们研究了高浓度的胞质环状GMP对完整细胞和分离的外节细胞中老虎蜥蜴杆的光电流动力学和光敏感性的影响。用含有cGMP的贴片吸管将cGMP注入感光细胞的内段或外段。只有当贴片吸管直接作用于外段时，外段胞浆中cGMP的浓度才能显著增加。暗电流幅度随cGMP浓度的增加而增加，最高可达1,400 pA。5.0mMcGMP内灌流使光电流延迟1~3个S。延迟的大小与光的强度成反比。此外，与完整细胞相比，闪光后1 S测得的光电流时间进程减慢，光敏感度降低约100倍。将观察到的cGMP效应与假设初始光电流时间过程由光激活的磷酸二酯酶(PDE)的动力学和光敏通道的cGMP依赖性决定的模型预测的结果进行了比较。在高浓度的cGMP作用下，根据光激活的PDE和cGMP激活的通道的已知生化特性，实验数据与模型预测的结果相似。
We investigated the effects of high concentrations of cytoplasmic cyclic GMP on the photocurrent kinetics and light sensitivity of the tiger salamander rod both in intact cells and in detached outer segments. Photoreceptors were internally perfused with cGMP by applying patch pipettes containing cGMP to the inner or outer segment. Large increases in the concentration of cGMP in the outer segment cytoplasm were achieved only when the patch pipette was applied directly to the outer segment. The dark-current amplitude increased with increasing cGMP concentrations up to approximately 1,400 pA. Internal perfusion with 5.0 mM cGMP introduced a delay of 1-3 s in the photocurrent. The magnitude of the delay was inversely proportional to the light intensity. In addition, the photocurrent time course was slowed down and the light sensitivity, measured 1 s after the flash, was decreased approximately 100-fold when compared with that of the intact cell. The observed effects of cGMP were compared with those predicted by a model that assumes that the initial photocurrent time course is determined by the kinetics of the light-activated phosphodiesterase (PDE) and the cGMP dependence of the light-sensitive channels. At high concentrations of cGMP, the experimental data were similar to those predicted by the model and based on the known biochemical properties of the light- activated PDE and cGMP-activated channels.