RHODOPSIN KINETICS IN HUMAN EYE
RHODOPSIN KINETICS IN HUMAN EYE
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DOI：
10.1113/jphysiol.1971.sp009580
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发表时间：
1971-01-01
影响因子：
5.5
通讯作者：
ALPERN, M
中科院分区：
文献类型：
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作者：
ALPERN, M
1. 通过Rushton的反射密度测定法，在视网膜颞部到中央凹的18°区域测量了视紫红质，使用的测量光的波长（555nm）到目前为止已经进入了光谱的长波部分，可能的蓝色吸收中间体（例如瞬变橙色）不会干扰。视紫红质在强光下漂白10秒，然后在较弱的光下保持稳定。在10秒的漂白过程中，没有再生发生，漂白的速度与量子捕获成正比。比例常数约为10−7(td sec)−1.3。由2，计算了稳定光在平衡状态下产生的光解速率。由于条件处于平衡状态，光解反应与再生反应相匹配。研究发现，生成速率与仍在漂白的色素数量成正比。比例常数约为0·0025 sec−1.4。通过几种不同的方法发现，3中的常数在光照或黑暗中是相同的，因此再生与漂白无关。因此，将漂白和再生实验的结果结合起来，可以得到一般的公式[公式：见文]，其中为视紫红质的含量，为秒，为视网膜照度。这个方程描述了在各种不同的中等长时间（至少10分钟）暴露强度下的部分漂白和再生实验的结果。杆状单色视者视网膜周围区域的暗适应曲线在近7 log10个单位的范围内遵循简单的指数过程。该区域的视紫红质再生和对数阈值用同一曲线描述，时间常数约为400秒，阈值每下降一个对数单位，视紫红质就增加0.835%。这个时间常数与Rushton（1961）的发现一致，但比Ripps & Weale （1969a）报告的时间要长得多。然而，Ripps和Weale的结果是通过非常短的明亮氙气闪光漂白获得的（就像他们所做的那样）。在此条件下，形成了吸蓝中间体，紫红质再生的时间常数比长时间漂白后的时间常数快得多，动力学方程不成立。一般方程，连同在7中发现的关系，成功地解释了其他人先前发表的关于漂白持续时间和强度对黑暗中杆状阈值恢复的影响的结果，前提是超过5%的视紫红质在黑暗适应开始时被漂白。
1. Rhodopsin has been measured by Rushton's method of reflexion densitometry in a retinal region 18° temporal to the fovea, using a wavelength of measuring light (555 nm) so far into the long wave part of the spectrum that possible blue absorbing intermediates (e.g. transient orange) do not interfere.2. Rhodopsin was bleached by a strong light for 10 sec and then held steady by a weaker light. During a 10 sec bleach, no regeneration occurs and the rate of bleaching is proportional to the quantum catch. The proportionality constant is about 10−7(td sec)−1.3. From 2, the rate of photolysis at equilibrium produced by the steady light was calculated. Since conditions were at equilibrium, photolysis matched regeneration. It was found that the rate of generation was proportional to the amount of pigment still bleached. The proportionality constant was about 0·0025 sec−1.4. It was found by several different methods that the constant in 3 is the same in the light or dark and hence regeneration occurs independently of bleaching.5. Therefore, the results from bleaching and regeneration experiments can be combined to give the general equation [Formula: see text], wherepis the fraction of rhodopsin,tis time in sec andIis the retinal illuminance.6. This equation describes the results of partial bleaching and regeneration experiments under a variety of different exposure intensities of moderately long (at least 10 min) exposure durations.7. The dark adaptation curve in a peripheral region of the rod monochromat's retina where there are few cones follows a simple exponential course over nearly 7 log10units. Rhodopsin regeneration and log threshold for this region are described by the same curve with a time constant of about 400 sec. Each log unit fal in threshold is accompanied by 0·835% increase in rhodopsin. This time constant is in agreement with Rushton's (1961) finding, but appreciably longer than that reported by Ripps & Weale (1969a).8. The Ripps & Weale result was, however, obtained by bleaching with a very short bright xenon flash (as they did). Under these conditions, blue absorbing intermediate(s) is (are) formed, the time constant of regeneration of rhodopsin is much faster than after long tungsten bleaches, and the kinetic equation is not valid.9. The general equation, together with the relation found in 7, successfully accounts for results previously published by others of the effect of duration and intensity of bleaching on the recovery of rod threshold in the dark, provided only that more than 5% of the rhodopsin was bleached at the beginning of dark adaptation.