EFFECT OF XENOBIOTICS ON THE RESPIRATORY ACTIVITY OF RAT-HEART MITOCHONDRIA AND THE CONCOMITANT FORMATION OF SUPEROXIDE RADICALS

The effects of the xenobiotics atrazine, benzene, butylated hydroxyani sole (BHA), butylated hydroxytoluene (BHT), lindane, toluene, and xyle nol on the respiration of isolated rat heart mitochondria were studied . Bioenergetic parameters such as respiratory control (RC) and ATP/oxy gen (P/0) values decreased considerably in the presence of these subst ances, and a concomitant increase of superoxide radical (02.-) formati on was observed. These observations were discussed in terms of partial damage of the inner mitochondrial membrane, impairing the maintenance of the proton gradient across this membrane. In the presence of proto ns, ubisemiquinone radicals (UQ.-) present in the inner mitochondrial membrane are able to react with molecular oxygen, thereby generating s uperoxide radicals. The changes of membrane potential and P/0 values s how a linear inverse correlation with 0.2- formation rates, whereas th is correlation with RC values was not linear.