Enhancement of altered hepatic foci in rat liver and inhibition of intercellular communication in vitro by the pyrethroid insecticides fenvalerate, flucythrinate and cypermethrin.
Male Sprague-Dawley rats dosed with N-nitrosodiethylamine (NDEA) 24 h after two-thirds partial hepatectomy were treated with the pyrethroid insecticides fenvalerate, flucythrinate or cypermethrin in the diet for 20 weeks. Altered hepatic foci were analyzed by quantitative stereology from paraffin-embedded sections stained for gamma-glutamyltranspeptidase (GGT) or glutathione S-transferase P (GST-P). The present results demonstrate that the pyrethroids tested all enhance the development of NDEA-initiated, GGT-positive foci in rat liver at non-hepatotoxic doses. On the contrary, the volume fractions of GST-P-positive foci were not elevated as compared to the control group. The three pyrethroids tested all inhibited the transfer of Lucifer Yellow CH between WB-F344 rat liver epithelial cells in culture, supporting the increase of GGT-positive foci and suggesting that these substances can act as tumour promoters. The discrepancy between the results from analyses using GGT or GST-P as markers emphasizes the importance of understanding the mechanism underlying the expression of different markers for preneoplastic lesions and the importance of such effects in tumour promotion.[1]References
- Enhancement of altered hepatic foci in rat liver and inhibition of intercellular communication in vitro by the pyrethroid insecticides fenvalerate, flucythrinate and cypermethrin. Hemming, H., Flodström, S., Wärngård, L. Carcinogenesis (1993) [Pubmed]
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