INTERACTIONS OF 2,2-BIS(P-CHLOROPHENYL)-1,1-DICHLOROETHYLENE WITH MITOCHONDRIAL OXIDATIVE-PHOSPHORYLATION

The effects of DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethylene), the major metabolite of DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethan e), on rat liver mitochondrial bioenergetic activities were examined. The approach developed by M. D. Brand (Biochim Biophys Acta 1018: 128- 133, 1990) was used to assess the effects of DDE because it is possibl e to discriminate the sites of action of compounds having pleiotypic e ffects on oxidative phosphorylation. Data were further confirmed using a ''classical'' approach, including measurements of transmembrane pot ential, respiratory indexes, enzymatic activities and membrane permeab ility to protons. DDE up to 40 nmol/mg protein affected the proton mot ive force generating system. In fact, DDE interacted with succinate de hydrogenase (complex II), decreasing respiration and membrane potentia l. In this concentration range, the permeability of the inner membrane to protons remained intact. Only higher concentrations (greater than or equal to 80 nmol/mg) increased permeability to protons, uncoupling oxidation from phosphorylation. The phosphorylative system was not aff ected because the rate of ATP synthesis was unchanged. In addition, da ta from carbonyl cyanide m-chlorophenylhydrazone-uncoupled rotenone-in hibited preparations or submitochondrial particles indicated that F0F1 ATPase activity is not affected by DDE. Therefore, DDE inhibition of complex II and putative inhibition of succinate translocation explain the depression of mitochondrial respiration. The use of appropriate su bstrates and assay conditions indicates that complexes I, III and IV w ere not affected by DDE. The uncoupling of oxidative phosphorylation a t high concentrations (>80 nmol DDE/mg protein) was probably related t o deleterious effects on the integrity of the mitochondrial membrane. We confirmed that the technique originally proposed by Brand is useful for characterizing the effects of xenobiotics on oxidative phosphoryl ation. In addition, data provided by this technique closely agree with data from classical studies. Copyright (C) 1997 Elsevier Science Inc.