Effects of hickory smoke condensate on gastric carcinogenesis in Wistar rats after treatment with N-methyl- N′-nitro- N-nitrosoguanidine and sodium chloride

Abstract

Short-term assays in vivo have suggested that hickory smoke condensate (HSC), a food flavouring, might have tumour-initiating and/or promoting activities in the glandular stomach of the rat. In the present study, the modifying effects of HSC on glandular stomach carcinogenesis after initiation with N-methyl- N′-nitro- N-nitrosoguanidine (MNNG) and sodium chloride (MNNG salt) were investigated in male Wistar rats. Animals were given MNNG solution (100 ppm) as drinking water and simultaneously fed the diet supplemented with 5% sodium chloride for 8 wk. Matched negative controls received neither MNNG nor sodium chloride. Rats were then fed a basal diet and given HSC solution (1 or 3%) or tap water for the following 32 wk. During the experimental period, treatment with MNNG salt and administration of HSC both brought about growth retardation although the final body weight of rats was comparable between groups. Only two rats treated with MNNG salt followed by 1% HSC developed adenocarcinoma of the stomach. HSC treatment appeared to increase the number of rats with preneoplastic hyperplasias and/or adenocarcinomas in both the fundic and pyloric mucosa, although not to a statistically significant extent. HSC administration significantly increased malondialdehyde levels in the urine and gastric mucosa, the former in a dose-dependent manner. The results suggest that HSC has little, if any, promoting effect on two-stage glandular stomach carcinogenesis in rats when given during the post-initiation phase. However, the tumour co-initiating effects of HSC require further clarification.