Early proliferative responses of forestomach and glandular stomach of rats treated with five different phenolic antioxidants.

The effects of 8 weeks of oral administration of five different phenolic antioxidants, e.g. catechol (CC), resorcinol, hydroquinone (HQ), 2-tert-butyl-4-methylphenol (TBMP) and propylparabene (PP), on forestomach and glandular stomach epithelium of male F344 rats were evaluated using a combined immunohistochemical and histopathological approach. Treatment with CC and TBMP induced a significant elevation of DNA synthesis in the forestomach epithelium, associated with hyperplasia. CC administration also brought about an increase of DNA synthesis in the pyloric gland mucosa, cell proliferation in this case being reflected by an increment in the crypt height. In addition to causing an increase in the pepsinogen-isozyme-1-altered pyloric glands (PAPG), which are considered to be putative preneoplastic precursor lesions in the rat glandular stomach, CC treatment was associated with submucosal growth of pyloric mucosal cells tending to decreased pepsinogen isoenzyme 1 binding. However, DNA synthesis values in these latter areas were lower than in pyloric glands of the control group. In contrast, other phenolic compounds, resorcinol, HQ and PP, did not induce any changes in the stomach mucosa. The present results demonstrated strong proliferative responses in the stomach epithelium for CC and TBMP, indicative of promoting potential in both cases, and suggest that CC and TBMP may exert detrimental effects leading to promotion of stomach carcinogenesis or cancer development via an early proliferative response.