Comparison of the in vitro toxicity of dichloroaniline structural isomers

Acute exposure to certain dichloroaniline (DCA) isomers results in renal and hepatic toxicity in vivo. In the present study we examined whether dichloroaniline structural isomers were cytotoxic to liver and kidney slices in vitro and compared the toxicities of the different structural isomers. These studies were necessary in order to validate the use of an in vitro slice system for examination of the cellular mechanisms for toxicity. Renal cortical and hepatic slices were incubated for 90 min with 2,3-DCA, 2,4-DCA, 2,5-DCA, 2,6-DCA, 3,4-DCA or 3,5-DCA at a final concentration of 0–1 m m. Pyruvate-directed gluconeogenesis was measured following an additional 30-min incubation with 10 m M pyruvate. Cytotoxicity was also determined by measurement of lactate dehydrogenase (LDH) release 120 min after the addition of dichloroaniline isomers at a final concentration of 0, 0.5, 1 or 2 m M. Gluconeogenesis in renal cortical slices was inhibited by all of the isomers beginning at a concentration of 0.5 m M. Renal slice LDH leakage was elevated above control levels by 1–2 m M 3,4-DCA or 3,5-DCA. A final concentration of 2 m M was needed for 2,3-DCA, 2,4-DCA, 2,5-DCA or 2,6-DCA in order to detect a significant ( P < 0.05) increase in renal slice LDH leakage. Hepatic slices incubated with 0.5–2 m M 2,3-DCA or 2 m M 2,5-DCA exhibited diminished pyruvate-directed gluconeogenesis. After exposure to 2,4-DCA, 2,6-DCA, 3,4-DCA or 3,5-DCA, pyruvate-directed gluconeogenesis was similar to that in the controls. LDH leakage was increased significantly ( P < 0.05) above control values by exposure to 2 m M 3,4-DCA or 3,5-DCA. In conclusion, DCA structural isomers were toxic in vitro to liver and kidney slices. These results indicated that the kidney was more sensitive than the liver to DCA isomers, and that the most toxic isomer was 3,5-DCA. These results are similar to those previously observed in vivo.