Lack of significant promoting activity by benzene in the rat liver model of carcinogenesis

Abstract

The promoting activity of benzene on rat liver carcinogenesis was investigated. The chemical was tested for its ability to enhance the growth of preneoplastic foci, as detected by gamma-glutamyl transpeptidase (GGT) staining in diethylnitrosamine (DENA) initiated hepatocytes. Two weeks after receiving a single ip dose of 200 mg/kg DENA, F344 rats were given daily oral doses of 400 mg/kg benzene (5 d/wk) for 6 wk. At wk 3 after the experiment began, all animals underwent partial hepatectomy, and at wk 8 were sacrificed. Following benzene treatment, no variation in the liver/body weight ratio was observed. After scoring of foci in liver slides, no significant difference in foci number and area could be observed between rats treated with DENA plus benzene and rats treated with DENA alone. Practically no foci were observed in the liver of rats treated only with benzene. The lack of benzene promoting activity in the liver model is discussed.

ATSDR evaluation of health effects of benzene and relevance to public health

“…A slight increase in the incidence of altered hepatic foci was observed after initiation and promotion. Few hepatic foci were observed in the livers of male Fischer 344 rats treated by gavage with 400 mg/kg/day benzene in corn oil for 5 days/week for 6 weeks (Taningher, et al, 1995). No histopathological non-neoplastic lesions were observed in hepatic tissue from male and female Fischer 344 rats given oral doses of 0, 25, 50, 100, 200, 400, or 600 mg/kg/day benzene in corn oil for 120 days or in male rats exposed to 50-200 mg/kg/day and female rats exposed to 25-100 mg/kg/day for 2 years (NTP, 1986).…”

“…No significant change in body weight was observed in male Fischer 344 rats treated by gavage with 400 mg/kg/day benzene in corn oil for 5 days/week for 6 weeks (Taningher, et al, 1995). Body weight was unaffected in male and female Fischer 344 rats given oral doses of 0, 25, 50, or 100 mg/kg/day benzene in corn oil for 120 days (NTP, 1986).…”