© 1992 Oxford University Press
research-article |
The insecticide endosulfan and its two stereoisomers promote the growth of altered hepatic foci in rats
1Institute of Environmental Medicine, Karolinska Institutet Box 60208, S-104 01 Stockholm
2Department of Toxicology, Karolinska Institutet Box 60400, S-104 01 Stockholm, Sweden
3To whom correspondence should be addressed
The non-genotoxic, chlorinated cyclodiene insecticide endosulfan was studied for its ability to act as a tumour promoter in a two-stage, altered hepatic foci bioassay in male Sprague-Dawley rats. Two stereoisomers of endosulfan, 
-endosulfan (ENDO) and ß-endosulfan (ENDOß3) were used, as well as a commercially-occurring mixture of the -and ß-isomers (ENDOß). The animals were initiated by intraperitoneal injection of nitrosodiethylamine 24 h after a two-thirds-partial hepatectomy. Five weeks later the animals were transferred to diets containing 30, 100 and 300 p.p.m. of either ENDOß, END or ENDOß. The study was terminated 25 weeks after initiation and the development of foci of 
-glutamyltranspeptidase-positive hepatocytes was evaluated by stereological methods. The results show that endosulfan and its two stereoisomers promote the development of altered hepatic foci, suggesting that endosulfan is a tumour-promoting agent acting by clonal expansion of initiated cells.