ENHANCEMENT OF GST-P POSITIVE LIVER-CELL FOCI DEVELOPMENT BY A MEDIUM-TERM CARCINOGENICITY BIOASSAY USING REPEATED ADMINISTRATION OF D-GALACTOSAMINE

This study was performed for developing a new medium-term carcinogenic ity bioassay treated with D-galactosamine (DGA) as a non-surgical meth od without partial hepatectomy (PH). In male F344 rats initiated with diethylnitrosamine (DEN, 200 mg/kg i.p.), enhancing effects of DGA (30 0 mg/kg i.p.) given twice 3 weeks apart during the promotion procedure with 2-acetylaminofluorene (2-AAF, 0.01% in diet) were compared along with those of PH by analyzing preneoplastic glutathione S-transferase placental form positive (GST-P+) hepatocyte foci as endpoint marker l esions. The DGA treatment did not affect the body weight gain whereas the PH treatment caused a transient body weight loss. Although both bi oassay protocols were effective to detect the potential hepatocarcinog enicity of 2-AAF the number and area of GST-P positive foci per cm(2) were larger in the bioassay using DGA than in that using PH, the numbe r being statistically significant (P < 0.05). Our results thus suggest that the present bioassay protocol with repeated administration of DG A instead of PH may offer a new and sensitive method to screen large n umbers of environmental carcinogens.