Comparative studies on the production of stomach tumors following the intubation of several doses of N-methyl-N'-nitro-N-nitrosoguanidine in germ-free and conventional newborn rats.

The present work was undertaken to investigate the possible role of microflora in gastric tumorigenesis by the comparison of tumor production between germ-free and conventional male Wistar rats given the same amount of N-methyl-N'-nitro-N-nitrosoguanidine into the stomach by catheter during the newborn period. Only 29% of germ-free rats treated with 450 microgram/animal that were killed 300 days after the first intubation had tumors in the stomach, whereas 93% of conventional similarly treated rats had such tumors at the same period, suggesting that the microflora might exert a promoting influence upon stomach tumor production.