Chefurka W, Zahradka P, Bajura S T
Biochim Biophys Acta. 1980 Sep 18;601(2):349-57. doi: 10.1016/0005-2736(80)90539-8.
This study describes DDT-induced changes in membrane permeability of mitochondria and erythrocytes to K+ as monitored by a K+-selective electrode. DDT is a strong inhibitor of valinomycin-mediated K+ uptake and the corresponding H+ efflux and an inducer of K+ leakage out of mitochondria but not to any significant extent out of erythrocytes. The inhibition of K+ uptake and H+ efflux was a function of (a) preincubation time between mitochondria and DDT, (b) mitochondrial concentration, (c) the nature of the carrier solvent and (d) temperature. The kinetics of inhibition of K+ uptake showed that DDT is an uncompetitive inhibitor with respect to valinomycin and a competitive inhibitor with respect to K+. The efflux of endogenous K+ showed a sigmoid dependency on DDT concentration and was reduced to endogenous rates when the temperature was lowered below the gel-liquid crystalline phase transition of the lipids. It is suggested that the DDT-induced changes in membrane permeability are due to perturbation of the lipid phase and that its toxicity may be due in part to hyperpolarization of subcellular membranes.
本研究描述了通过钾离子选择性电极监测的滴滴涕（DDT）诱导的线粒体和红细胞膜对钾离子通透性的变化。DDT是缬氨霉素介导的钾离子摄取及相应氢离子外流的强效抑制剂，是线粒体钾离子渗漏的诱导剂，但对红细胞钾离子渗漏影响不大。钾离子摄取和氢离子外流的抑制作用取决于：（a）线粒体与DDT的预孵育时间；（b）线粒体浓度；（c）载体溶剂的性质；（d）温度。钾离子摄取抑制动力学表明，DDT对缬氨霉素而言是非竞争性抑制剂，对钾离子而言是竞争性抑制剂。内源性钾离子外流对DDT浓度呈S形依赖性，当温度降至低于脂质的凝胶 - 液晶相转变温度时，外流速率降至内源性水平。研究表明，DDT诱导的膜通透性变化是由于脂质相的扰动，其毒性可能部分归因于亚细胞膜的超极化。
