Active Potassium Ion Transport Across the Caterpillar Midgut: I. Tissue Electrical Properties and Potassium Ion Transport Inhibition
Active Potassium Ion Transport Across the Caterpillar Midgut: I. Tissue Electrical Properties and Potassium Ion Transport Inhibition
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穿过毛虫中肠的活性钾离子传输：I. 组织电特性和钾离子传输抑制
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
T. E. May
中科院分区：
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作者：
M. V. Thomas;T. E. May
本文用电学方法研究了离体棉贪夜蛾（Spodoptera littoralis）和烟草天蛾（Manduca sexta）幼虫中肠对钾离子的主动转运。与以前的研究相比，中肠的电特性基本上保持恒定的几个小时，这种改善可能是由于使用的实验盐水，更接近毛虫血淋巴。主动转运可以被缺氧和一些化学试剂所消除，其中氯化三甲基锡（在10 −9 M时有效）是最有效的。其中一些物质，包括三甲基氯化锡，可能直接作用于钾离子转运系统。改变盐水的离子组成的结果表明，钾是唯一可以以显著速率运输的阳离子。然而，钾离子转运的速率增加的同时存在的其他无机阳离子。通过改变钾离子浓度来确定主动运输途径的“逆转电位”的实验表明，该参数不是常数，因此主动运输系统不能由简单的等效电路来建模，尽管中肠上皮在这方面并不独特。因此，组织电特性不能容易地与钾转运过程的能量学相关联，但如果ATP确实是主要能量来源，则结果仍然与大于1的钾离子：ATP比率一致。
Active potassium ion transport by isolated midguts of Spodoptera littoralis and Manduca sexta caterpillars has been studied by electrical means. In contrast to previous studies, the electrical properties of the midguts remained essentially constant for several hours; this improvement probably results from use of an experimental saline that more closely resembles caterpillar haemolymph. The active transport could be abolished by anoxia and by a number of chemical agents, of which trimethyl tin chloride (effective at 10 −9 M) was the most potent. Some of these substances, including trimethyl tin chloride, may have been acting directly on the potassium ion transport system. The results of varying the ionic composition of the saline suggest that potassium is the only cation that can be transported at a significant rate. However, the rate of potassium ion transport is increased by the simultaneous presence of other inorganic cations. Experiments to determine the ‘reversal potential’ for the active transport pathway, by varying the potassium ion concentration, suggested that this parameter was not a constant, and thus the active transport system could not be modelled by a simple equivalent electrical circuit, although the midgut epithelium is not unique in this respect. Therefore, the tissue electrical properties could not readily be correlated with the energetics of the potassium transport process, but the results are nevertheless consistent with a potassium ion: ATP ratio of greater than one, if ATP is indeed the primary energy source.