Facilitation of the responses to injections of inositol 1,4,5-trisphosphate analogs in Limulus ventral photoreceptors.
Facilitation of the responses to injections of inositol 1,4,5-trisphosphate analogs in Limulus ventral photoreceptors.
复制标题
促进鲎腹侧光感受器对注射肌醇 1,4,5-三磷酸类似物的反应。
DOI：
10.1016/s0006-3495(94)80584-3
复制
发表时间：
1994
影响因子：
3.4
通讯作者：
Hillman,P
中科院分区：
文献类型：
--
作者：
Levitan,I;Payne,R;Potter,BV;Hillman,P
将肌醇1,4,5-三磷酸及其代谢抗性类似物InsP3S3和l -chiro-2,3,5- insp3注射到鲎的腹侧光感受器中，导致钙从内部储存中释放出来，并以电流流入细胞。我们在这里表明，电流响应对注入模拟量的依赖是超线性的。注射也促进了对后续注射的反应。我们通过缓慢地将类似物直接应用到对InsP3和光敏感的叶中，或通过将脉冲传递到细胞的非敏感叶中来分析响应的动力学，在这两种情况下，在敏感区域产生浓度上升的斜坡。典型的情况是，在一段很长的潜伏期之后，有一股短暂而强烈的内向气流。响应的潜伏期和持续时间之比（定义为从半振幅到响应峰值时间的两倍）达到大于10的值。我们的分析表明，这个值不能在现实模型中获得，其唯一的非线性是配体与其受体的合作结合。然而，观察到的比率可以通过正反馈模型来实现。导致钙储存部分消耗的治疗可逆地增加了反应的潜伏期。我们得出结论，腹侧鲎对代谢抗性类似物InsP3的反应机制可能涉及一种正反馈机制，而反馈的载体可能是Ca2+。
Injection of inositol 1,4,5-trisphosphate and its metabolically resistant analogs InsP3S3 and L-chiro-2,3,5-InsP3 into the ventral photoreceptors of Limulus results in the release of calcium from internal stores and in a current flow into the cells. We show here that the dependence of the current response on the amount of analog injected is supralinear. The injections also facilitate the responses to subsequent injections. We analyze the kinetics of the responses either by very slow application of the analogs directly into the lobe that is sensitive to InsP3 and light or by delivering a pulse into the nonsensitive lobe of the cell, in both cases creating a ramp of rising concentration in the sensitive region. Typically, a long latent period was followed by a strong brief inward current. The ratio between the latency and the duration of the response, defined as twice the time from half-amplitude to the peak of the response, reaches values greater than 10. Our analysis shows that this value cannot be attained within realistic models whose only nonlinearity is the cooperative binding of the ligand to its receptor. The observed ratio, however, can be achieved with a positive feedback model. Treatments that lead to partial depletion of calcium stores reversibly increase the latency of the response. We conclude that the mechanisms of the response of Limulus ventral eye to the metabolically resistant analogs of InsP3 probably involves a positive feedback mechanism and that the carrier of the feedback is likely to be Ca2+.