Tsacopoulos M, Poitry S
J Gen Physiol. 1982 Jul;80(1):19-55. doi: 10.1085/jgp.80.1.19.
The time course of the rate of oxygen consumption (QO2) after a single flash of light has been measured in 300-micrometers slices of drone retina at 22 degrees C. To measure delta QO2(t), the change in QO2 from its level in darkness, the transients of the partial pressure of O2 (PO2) were recorded with O2 microelectrodes simultaneously in two sites in the slice and delta QO2 was calculated by a computer using Fourier transforms. After a 40-ms flash of intense light, delta QO2, reached a peak of 40 microliters O2/g.min and then declined exponentially to the baseline with a time constant tau 1 = 4.96 +/- 0.49 s (SD, n = 10). The rising phase was characterized by a time constant tau 2 = 1.90 +/- 0.35 s (SD, n = 10). The peak amplitude of delta QO2 increased linearly with the log of the light intensity. Replacement of Na+ by choline, known to decrease greatly the light-induced transmembrane current, caused a 63% decrease of delta QO2. With these changes, however, the kinetics of delta QO2 (t) were unchanged. This suggest that the recovery phase is rate-limited by a single reaction with apparent first-order kinetics. Evidence is provided that suggests that this reaction may be the working of the sodium pump. Exposure of the retina to high concentrations of ouabain or strophanthidin (inhibitors of the sodium pump) reduced the peak amplitude of delta QO2 by approximately 80% and increased tau 1. The increase of tau 1 was an exponential function of the time of exposure to the cardioactive steroids. Hence, it seems likely that the greatest part of delta QO2 is used for the working of the pump, whose activity is the mechanism underlying the rate constant of the descending limb of delta QO2 (t).
在22摄氏度下，对雄蜂视网膜300微米厚的切片施加单次闪光后，测量了其耗氧率（QO2）的时间进程。为了测量δQO2(t)，即QO2相对于其在黑暗中的水平的变化，使用氧微电极在切片的两个部位同时记录O2分压（PO2）的瞬变，并通过计算机使用傅里叶变换计算δQO2。在40毫秒的强光闪光后，δQO2达到40微升O2/克·分钟的峰值，然后以时间常数τ1 = 4.96 ± 0.49秒（标准差，n = 10）指数下降至基线。上升阶段的时间常数为τ2 = 1.90 ± 0.35秒（标准差，n = 10）。δQO2的峰值幅度随光强度的对数呈线性增加。用胆碱替代Na+（已知会大大降低光诱导的跨膜电流）导致δQO2降低63%。然而，有了这些变化，δQO2(t)的动力学没有改变。这表明恢复阶段受具有明显一级动力学的单一反应的速率限制。有证据表明，该反应可能是钠泵的作用。将视网膜暴露于高浓度的哇巴因或毒毛花苷（钠泵抑制剂）会使δQO2的峰值幅度降低约80%，并增加τ1。τ1的增加是暴露于强心甾体时间的指数函数。因此，似乎很可能δQO2的最大部分用于泵的作用，其活性是δQO2(t)下降支速率常数的潜在机制。
