title: Inhibition of metabolic cooperation in vitro and enhancement of enzyme altered foci incidence in rat liver by the pyrethroid insecticide fenvalerate.
abstract: The synthetic pyrethroids cypermethrin, delta-methrin, fenvalerate, permethrin, and the fenvalerate metabolite p-chlorophenylisovaleric acid were investigated for inhibition of gap-junctional intercellular communication in vitro in the Chinese hamster lung fibroblast (V79) metabolic cooperation assay. Fenvalerate was furthermore studied for enhancement of gamma-glutamyl transpeptidase-positive enzyme altered foci incidence in partially hepatectomized, nitrosodiethylamine-initiated male Sprague Dawley rats. The in vitro studies showed that fenvalerate and p-chlorophenylisovaleric acid were inhibitors of intercellular communication at non-cytotoxic concentrations while cypermethrin, deltamethrin, and permethrin were inactive. In the in vivo study in rat liver, fenvalerate administered p.o. (75 mg/kg/day) 5 days a week for 10 weeks induced significantly more foci per cm3 and a larger percentage of liver tissue occupied by foci tissue compared to a vehicle control group. Analysis of size distributions of foci in fenvalerate- and vehicle-treated rats showed elevated foci incidences in fenvalerate-treated rats at all foci sizes. Fenvalerate induced no hepatotoxic effects as judged by plasma transaminase activities and histopathology. The results of this study suggest fenvalerate to be a potential tumour promoter.
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity*; D008099:Liver / Q000201:enzymology / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced*; D008297:Male; D009570:Nitriles; D011230:Precancerous Conditions / Q000139:chemically induced*; D011722:Pyrethrins / Q000378:metabolism / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains; D005723:gamma-Glutamyltransferase / Q000032:analysis
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D005723:gamma-Glutamyltransferase; C017690:fenvalerate