Brown J E, Blinks J R
J Gen Physiol. 1974 Dec;64(6):643-65. doi: 10.1085/jgp.64.6.643.
Aequorin, which luminesces in the presence of calcium, was injected into photoreceptor cells of Limulus ventral eye. A bright light stimulus elicited a large increase in aequorin luminescence, the aequorin response, indicating a rise of intracellular calcium ion concentration, Ca(i). The aequorin response reached a maximum after the peak of the electrical response of the photoreceptor, decayed during a prolonged stimulus, and returned to an undetectable level in the dark. Reduction of Ca(o) reduced the amplitude of the aequorin response by a factor no greater than 3. Raising Ca(o) increased the amplitude of the aequorin response. The aequorin response became smaller when membrane voltage was clamped to successively more positive values. These results indicate that the stimulus-induced rise of Ca(i) may be due in part to a light-induced influx of Ca and in part to release of Ca from an intracellular store. Our findings are consistent with the hypothesis that a rise in Ca(i) is a step in the sequence of events underlying light-adaptation in Limulus ventral photoreceptors. Aequorin was also injected into photoreceptors of Balanus. The aequorin responses were similar to those recorded from Limulus cells in all but two ways: (a) A large sustained aequorin luminescence was measured during a prolonged stimulus, and (b) removal of extracellular calcium reduced the aequorin response to an undetectable level.
水母发光蛋白在有钙存在时会发光，将其注入鲎腹眼的光感受器细胞中。强光刺激会使水母发光蛋白的发光大幅增加，即水母发光蛋白反应，这表明细胞内钙离子浓度（Ca(i)）升高。水母发光蛋白反应在光感受器电反应峰值之后达到最大值，在长时间刺激过程中衰减，并在黑暗中恢复到检测不到的水平。降低细胞外钙（Ca(o)）会使水母发光蛋白反应的幅度降低不超过3倍。升高Ca(o)会增加水母发光蛋白反应的幅度。当膜电压钳制在越来越正的数值时，水母发光蛋白反应会变小。这些结果表明，刺激诱导的Ca(i)升高可能部分归因于光诱导的钙内流，部分归因于细胞内储存钙的释放。我们的发现与以下假设一致，即Ca(i)升高是鲎腹侧光感受器光适应基础事件序列中的一个步骤。水母发光蛋白也被注入藤壶的光感受器中。水母发光蛋白反应与从鲎细胞记录到的反应相似，但有两点不同：（a）在长时间刺激期间测量到大量持续的水母发光蛋白发光，（b）去除细胞外钙会使水母发光蛋白反应降低到检测不到的水平。
