ABSTRACT
Glitazones, used for type II diabetes, have been associated with liver damage in humans. A structural feature known as a 2,4‐thiazolidinedione (TZD) ring may contribute to this toxicity. TZD rings are of interest since continued human exposure via the glitazones and various prototype drugs is possible. Previously, we found that 3‐(3,5‐dichlorophenyl)‐2,4‐thiazolidinedione (DCPT) was hepatotoxic in rats. To evaluate the importance of structure on DCPT toxicity, we therefore studied two series of analogs. The TZD ring was replaced with: a mercaptoacetic acid group {[[[(3,5‐dichlorophenyl)amino]carbonyl]thio]acetic acid, DCTA}; a methylated TZD ring [3‐(3,5‐dichlorophenyl)‐5‐methyl‐2,4‐thiazolidinedione, DPMT]; and isomeric thiazolidinone rings [3‐(3,5‐dichlorophenyl)‐2‐ and 3‐(3,5‐dichlorophenyl)‐4‐thiazolidinone, 2‐DCTD and 4‐DCTD, respectively]. The following phenyl ring‐modified analogs were also tested: 3‐phenyl‐, 3‐(4‐chlorophenyl)‐, 3‐(3,5‐dimethylphenyl)‐ and 3‐[3,5‐bis(trifluoromethyl)phenyl]‐2,4‐thiazolidinedione (PTZD, CPTD, DMPT and DFMPT, respectively). Toxicity was assessed in male Fischer 344 rats 24 h after administration of the compounds. In the TZD series only DPMT produced liver damage, as evidenced by elevated serum alanine aminotransferase (ALT) activities at 0.6 and 1.0 mmol kg^−1^ (298.6 ± 176.1 and 327.3 ± 102.9 Sigma‐Frankel units ml^−1^, respectively) vs corn oil controls (36.0 ± 11.3) and morphological changes in liver sections. Among the phenyl analogs, hepatotoxicity was observed in rats administered PTZD, CPTD and DMPT; with ALT values of 1196.2 ± 133.6, 1622.5 ± 218.5 and 2071.9 ± 217.8, respectively (1.0 mmol kg^−1^ doses). Morphological examination revealed severe hepatic necrosis in these animals. Our results suggest that hepatotoxicity of these compounds is critically dependent on the presence of a TZD ring and also the phenyl substituents. Copyright © 2011 John Wiley & Sons, Ltd.