[Effect of vitamin A deficiency on PNUR-induced carcinogenesis in the rat upper digestive tract].

The effects of vitamin A (VA) deficiency on 1-propyl-1-nitrosourethan (PNUR)-induced tumorigenesis in the upper digestive tract were investigated in male F344 rats. Starting at 6 weeks old, animals were given PNUR in the drinking water (200 ppm) for one week, and starting 2 weeks later, were divided into 3 groups (30 rats/group) and maintained on VA-deficient diet, VA-supplemented diet (semipurified diet) or standard diet (CRF-1), respectively. An additional control group (10 rats) was fed VA-deficient diet without PNUR treatment. The experiment was terminated at 41 weeks after the beginning of PNUR administration, and development of tumors in the upper digestive tract was determined histopathologically. Squamous cell tumors were observed in the oral cavity, tongue and forestomach of all PNUR treated groups, while no tumors developed in the control group. Significantly higher incidences of forestomach papillomas were observed in the groups administered VA-deficient or VA-supplemented diets, as compared with that receiving standard diet (p less than 0.01, p less than 0.05, respectively). These results thus suggest that the higher incidences of forestomach tumors were probably due to general dietary differences (semipurified vs. standard diets) and not to the VA deficiency per se.