Mitochondrial bioenergetics is affected by the herbicide paraquat

• Published in: Biochimica et biophysica acta 1995-04, Vol.1229 (2), p.187-192
• Main Authors: Palmeira, Carlos M., Moreno, António J., Madeira, Vítor M.C.
• Format: Article
• Language: English
• Subjects: agrochemicals; animal health; Animals; Energy Metabolism - drug effects; Herbicide toxicity; human health and safety; Intracellular Membranes - drug effects; Intracellular Membranes - metabolism; Intracellular Membranes - physiology; Male; medicine; Membrane Potentials; Mitochondria, Liver - drug effects; Mitochondria, Liver - metabolism; Mitochondria, Liver - physiology; Mitochondrion; Oxygen - metabolism; Paraquat; Paraquat - toxicity; pesticides; Rats; Rats, Wistar; Superoxide; veterinary medicine
• ISSN: 0005-2728; 0006-3002; 1879-2650; 1878-2434
• DOI: 10.1016/0005-2728(94)00202-G

The potential toxicity of the herbicide paraquat (1,1-dimethyl-4,4′-bipyridylium dichloride) was tested in bioenergetic functions of isolated rat liver mitochondria. Paraquat increases the rate of State 4 respiration, doubling at 10 mM, indicating uncoupling effects. Additionally, State 3 respiration is depressed by about 15%, at 10 mM paraquat, whereas uncoupled respiration in the presence of CCCP is depressed by about 30%. Furthermore, paraquat partially inhibits the ATPase activity through a direct effect on this enzyme complex. However, at high concentrations (5–10 mM), the ATPase activity is stimulated, probably as consequence of the described uncoupling effect. Depression of respiratory activity is mediated through partial inhibitions of mitochondrial complexes III and IV. Paraquat depresses Δψ as a function of herbicide concentration. In addition, the depolarization induced by ADP is decreased and repolarization is biphasic suggesting a double effect. Repolarization resumes at a level consistently higher than the initial level before ADP addition, for paraquat concentrations up to 10 mM. This particular effect is clear at 1 mM paraquat and tends to fade out with increasing concentrations of the herbicide.