In chronic carcinogenic bioassays, chemicals being tested with low water solubility have been administered via
corn oil gavage. The present study examined the effect of chronic
corn oil gavage on hepatic
tumor formation in the B6C3F1 male mouse. Mice were initiated with
diethylnitrosamine (DENA) either at 15 days of age with a single i.p. injection (5 micrograms/gbw) (protocol 1) or at 4 weeks of age via the
drinking water (15 mg/l) for a duration of 3 weeks (protocol 2). At weaning (protocol 1) or 8 weeks of age (protocol 2) initiated and untreated mice were administered either
corn oil at a dose of 0.15 ml via gavage (once a day, 5 days/wk) or saline (0.15 ml via gavage, once a day 5 days/wk). All mice were killed at 28 weeks of age and hepatic lesions were quantitated. Only mice exposed to DENA demonstrated hepatic
tumors. Mice treated with DENA (at 15 days of age) and
corn oil gavage exhibited a significant decrease in the number of hepatic
adenomas compared with DENA (at 15 days of age) only treated mice. No difference was noted in the number of hepatic
adenomas between mice treated with DENA (at 4 wks of age) and
corn oil gavage and mice exposed to DENA (at 4 wks of age) only.