The effect of the long-term feeding of raw soy flour on the pancreas of the mouse and hamster.

The effects of the long-term feeding of mice and hamsters with raw (RSF) or heated (HSF) soy flours were investigated both in the presence and absence of chemical carcinogens. Mice which had been fed RSF for 18 months had enlarged pancreas but only a relatively low incidence of atypical acinar cell nodules (AACN). Mice on either RSF or HSF were also relatively resistant to the carcinogenic effects of azaserine which is known to produce a high incidence of AACN in rats. Hamsters which had been fed RSF for 15 months did not exhibit pancreatic enlargement and had a very low incidence of pancreatic tumors. Although the incidence of tumors in hamsters which had been injected with N-nitrosobis (2-oxopropyl)amine and maintained on HSF was very high (88%), those on RSF had a tumor incidence of less than 10%. Thus, there appears to be a marked difference in the response of the pancreas in different species of animals to the long-term effects of feeding RSF. This should be taken into consideration in evaluating the potential carcinogenicity of the trypsin inhibitors.