Oxidants act as chemorepellents in Paramecium by stimulating an electrogenic plasma membrane reductase activity.
Oxidants act as chemorepellents in Paramecium by stimulating an electrogenic plasma membrane reductase activity.
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氧化剂通过刺激生电质膜还原酶活性在草履虫中充当化学驱避剂。
DOI：
10.1007/bf00199486
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Francis,JT
中科院分区：
文献类型：
--
作者：
Hennessey,TM;Frego,LE;Francis,JT
草履虫是研究化学感觉转导、适应和细胞感觉整合的有价值的真核模型系统。虽然毫摩尔量的许多引诱剂会超极化并导致更快的向前游泳，但氧化剂是驱避剂，在微摩尔浓度下会使人去极化并导致向后游泳。非过氧剂细胞色素c、硝基蓝四氮唑和铁氰化物是驱避剂，其半数最大浓度分别为0.4μM、2.2μM和100μM。在体内，还原酶的活性遵循相同的效力顺序。细胞色素c还原酶活性的浓度依赖关系与细胞色素c诱导的去极化密切相关。这表明外源细胞色素c的质膜还原是电生的，导致膜去极化和化学斥力。还原酶的活性似乎也是电压依赖的。K+、Na+、Ca+或Mg+的去极化与体内还原酶活性的抑制和细胞色素c诱导的膜电位变化有关。在纤毛细胞中也可以看到这些反应，表明身体质膜足以进行反应。氯喹和二苯基碘都能抑制还原酶活性，但只有在异常高的浓度下才能抑制。该酶活性在生理范围内无pH依赖性。我们认为，质膜结合的NADPH依赖的还原酶控制氧化剂诱导的去极化和随后的化学排斥。
Parameciumis a valuable eukaryotic model system for studying chemosensory transduction, adaptation and cellular sensory integration. While millimolar amounts of many attractants hyperpolarize and cause faster forward swimming, oxidants are repellents that depolarize and cause backward swimming at micromolar concentrations. The non-permeant oxidants cytochrome c, nitro blue tetrazolium and ferricyanide are repellents with half maximal concentrations of 0.4 μM, 2.2 μMand 100 μMrespectively. In vivo reductase activities follow the same order of potencies. The concentration dependence of the cytochrome c reductase activity is well correlated with cytochrome c-induced depolarizations. This suggests that plasma membrane reduction of external cytochrome c is electrogenic, causing membrane depolarization and chemorepulsion. The reductase activity also appears to be voltage dependent. Depolarization by either K+, Na+, Ca+ or Mg+ correlates with inhibition of both in vivo reductase activities and cytochrome c-induced membrane potential changes. These responses were also seen in deciliated cells, showing that the body plasma membrane is sufficient for the response. Both chloroquine and diphenyleneiodonium inhibited reductase activities but only at unusually high concentrations. This activity showed no pH dependence in the physiological range. We propose that a plasma membrane bound NADPH-dependent reductase controls oxidant-induced depolarizations and consequent chemorepulsion.