S-(1,2-dichlorovinyl)-L-homocysteine-induced cytotoxicity in isolated rat kidney cells.

Incubation of isolated, rat kidney cells with S-(1,2-dichlorovinyl)-L-homocysteine (DCVHC) caused time-dependent cell death. Cytotoxicity of DCVHC was potentiated by addition of alpha-ketobutyrate, indicating the involvement of pyridoxal phosphate-dependent enzymes. A second addition of DCVHC to cells produced increased cytotoxicity, indicating that the bioactivating ability is not lost after exposure to the conjugate. DCVHC decreased cellular glutathione concentrations by 52% and substantially inhibited glutathione biosynthesis from precursors. In contrast, the cysteine analog S-(1,2-dichlorovinyl)-L-cysteine (DCVC) failed to decrease cellular glutathione concentrations and only partially inhibited glutathione biosynthesis. As with DCVC, DCVHC did not increase cellular glutathione disulfide concentrations and did not initiate lipid peroxidation, indicating that it does not produce an oxidative stress. DCVHC and DCVC produced similar alterations in mitochondrial function: Cellular ATP concentrations were decreased by 57% and cellular ADP and AMP concentrations were increased twofold, thereby decreasing the ATP/ADP ratio from 2.8 to 0.6 and the cellular energy charge from 0.80 to 0.56; DCVHC was a potent inhibitor of succinate-dependent oxygen consumption, but had little effect on respiration linked to oxidation of glutamate + malate or ascorbate + N,N,N'N'-tetramethyl-p-phenylenediamine. DCVHC was a potent inhibitor of mitochondrial Ca2+ sequestration and, in contrast to DCVC, also inhibited microsomal Ca2+ sequestration. These DCVHC-induced alterations in cellular metabolism were prevented by addition of propargylglycine or aminooxyacetic acid, and the alpha-methyl analog S-(1,2-dichlorovinyl)-DL-alpha-methylhomocysteine was not toxic. These results support a role for pyridoxal phosphate-dependent bioactivation of DCVHC and indicate that the greater nephrotoxic potency of DCVHC as compared to DCVC is partially due to the presence of both mitochondrial and extramitochondrial targets for DCVHC.