Lack of promoting activity of four pesticides on induction of preneoplastic liver cell foci in rats.

T Kato, T Ogiso, K Kato, M Sano, R Hasegawa, T Shirai, N Ito

Index: Teratog. Carcinog. Mutagen. 15(5) , 251-7, (1995)

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Abstract

Four pesticides were examined for hepatopromoting activity using a medium-term bioassay based upon induction of glutathione S-transferase placental form (GST-P) positive foci in the rat liver. Male F344 rats were initially injected with diethylnitrosamine (DEN; 200 mg/kg body weight) intraperitoneally and 2 weeks later were treated with O-ethyl O-4-nitrophenyl phenylphosphonothioate (EPN; 75 and 150 ppm), diazinon (500 and 1,000 ppm), phenthoate (500 and 1,000 ppm), or iprobenfos (500 and 1,000 ppm) in the diet for 6 weeks and then killed, all rats being subjected to partial hepatectomy at week 3. All of the pesticides gave negative results, the numbers and areas of GST-P positive foci not exceeding the control values for animals given DEN alone. Indeed, a significant reduction of foci development was seen for EPN (75 ppm). These findings provide experimental evidence that the presently examined four pesticides do not have hepatocarcinogenic potential in rats.