Calcium regulates some, but not all, aspects of light adaptation in rod photoreceptors
Calcium regulates some, but not all, aspects of light adaptation in rod photoreceptors
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钙调节杆状光感受器光适应的一些但不是全部方面
DOI：
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
M. Bownds
中科院分区：
文献类型：
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作者：
G D Nicol;M. Bownds
通过使用钙离子载体 A23187 和外部 Ca2+ 缓冲液控制细胞内 Ca2+ 浓度，检查了钙作为视杆光感受器光适应调节剂的作用。这些研究利用了分离和纯化的青蛙杆外节的悬浮液，保留了富含线粒体的内节（OS-IS）。暗适应和光适应闪光响应的三个标准被表征为 Ca2+ 浓度的函数：(a) 达到峰值的时间，(b) 恢复率，以及 (c) 响应幅度或灵敏度。对于所有检查的 Ca2+ 浓度，在背景照明存在的情况下，闪光响应达到峰值的时间都会加快，这表明控制这方面适应的机制与 Ca2+ 浓度无关。闪蒸响应的恢复动力学似乎取决于 Ca2+ 浓度。在 1 mM Ca2+-Ringer's 和 300 nM Ca2+- Ringer's + A23187 中，背景照明增强了响应的恢复率；然而，在 10 和 100 nM Ca2+-Ringer's + A23187 中，暗适应和光适应反应的恢复率相同。这一结果表明，背景照明可能需要达到临界水平的 Ca2+，以加速闪光响应的恢复。黑暗中闪光响应 (SDF) 的灵敏度取决于 Ca2+ 浓度。在 1 mM Ca2+-Ringer 的 SDF 中，每个漂白视紫红质 (Rh*) 的 SDF 为 0.481 pA；四个 Rh*/s 的背景使 SDF 减少一半 (Io)。在 300 nM Ca2+ + A23187 下，SDF 降低至 0.0307 pA/Rh*，Io 增加至 60 Rh*/s。在 100 nM Ca2+ + A23187 下，SDF 进一步降低至 0.0025 pA/Rh*，Io 增加至 220 Rh*/s。在 10 nM Ca2+ + A23187 中，SDF 降低至 0.00045 pA/Rh*，Io 升高至 760 RhI/s。使用每个相应 Ca2+ 浓度的 SDF 和 Io 值，可以通过 Weber-Fechner 关系来描述闪光灵敏度对背景强度的依赖性。在低 Ca2+ 条件下 + A23187，明亮的背景照明可能会降低闪光响应的灵敏度。这些结果与 Ca2+ 浓度可能决定黑暗中响应灵敏度的绝对大小的观点一致，并且存在能够在细胞质 Ca2+ 浓度没有显着变化的情况下适应光响应的机制。
The role of calcium as a regulator of light adaptation in rod photoreceptors was examined by manipulation of the intracellular Ca2+ concentration through the use of the calcium ionophore A23187 and external Ca2+ buffers. These studies utilized suspensions of isolated and purified frog rod outer segments that retain their mitochondria- rich inner segments (OS-IS). Three criteria of the dark- and light- adapted flash response were characterized as a function of the Ca2+ concentration: (a) the time to peak, (b) the rate of recovery, and (c) the response amplitude or sensitivity. For all Ca2+ concentrations examined, the time to peak of the flash response was accelerated in the presence of background illumination, suggesting that mechanisms controlling this aspect of adaptation are independent of the Ca2+ concentration. The recovery kinetics of the flash response appeared to depend on the Ca2+ concentration. In 1 mM Ca2+-Ringer's and 300 nM Ca2+- Ringer's + A23187, background illumination enhanced the recovery rate of the response; however, in 10 and 100 nM Ca2+-Ringer's + A23187, the recovery rates were the same for dark- and light-adapted responses. This result implies that a critical level of Ca2+ may be necessary for background illumination to accelerate the recovery of the flash response. The sensitivity of the flash response in darkness (SDF) was dependent on the Ca2+ concentration. In 1 mM Ca2+-Ringer's SDF was 0.481 pA per bleached rhodopsin (Rh*); a background of four Rh*/s decreased SDF by half (Io). At 300 nM Ca2+ + A23187, SDF was reduced to 0.0307 pA/Rh* and Io increased to 60 Rh*/s. At 100 nM Ca2+ + A23187, SDF was reduced further to 0.0025 pA/Rh* and Io increased to 220 Rh*/s. In 10 nM Ca2+ + A23187, SDF was lowered to 0.00045 pA/Rh* and Io raised to 760 RhI/s. Using these values of SDF and Io for each respective Ca2+ concentration, the dependence of the flash sensitivity on background intensity could be described by the Weber-Fechner relation. Under low Ca2+ conditions + A23187, bright background illumination could desensitize the flash response. These results are consistent with the idea that the concentration of Ca2+ may set the absolute magnitude of response sensitivity in darkness, and that there exist mechanisms capable of adapting the photoresponse in the absence of significant changes in cytoplasmic Ca2+ concentration.
控制虎钝口螈视网膜孤杆中的发电机电流。
DOI：
10.1113/jphysiol.1984.sp015131
发表时间：
1984
期刊：
The Journal of physiology
影响因子：
--
作者：
MacLeish,PR;Schwartz,EA;Tachibana,M
通讯作者：
Tachibana,M
钙在调节视网膜视杆光转导环 GMP 级联中的作用。
DOI：
10.1073/pnas.83.18.7109
发表时间：
1986
影响因子：
11.1
作者：
Torre,V;Matthews,HR;Lamb,TD
通讯作者：
Lamb,TD
乌龟视网膜中杆状光感受器之间缺乏适应传播。
DOI：
10.1113/jphysiol.1985.sp015894
发表时间：
1985
期刊：
The Journal of physiology
影响因子：
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作者：
Copenhagen,DR;Green,DG
通讯作者：
Green,DG