Multiple carcinogenic effects of the ethylnitrosourea precursors ethylurea and sodium nitrite in hamsters.

SUMMARY The simultaneous p.o. administration of ethylnitrosourea precursors ethylurea and sodium nitrite (NaNO2) to adult hamsters at daily dosages of 100 and 50 mg/kg for a total of 40 dosages during the first 6 weeks of the experiment resulted in the induction of multiple types of neoplasms. Eighty-five % of the treated animals developed an average of over three tumors per tumor-bearing animal. However, only 14% of the animals treated with ethylurea alone for the same duration at doses of 100 mg/kg had single tumors, while 16% of the untreated controls also developed single neoplasms. The incidence of vascular tumors in the spleen and liver, papillomas of the forestomach and vagina, ovarian tumors, and neurogenic tumors in the peripheral nervous system was significant. However, lower frequencies were noted for some neoplasms that rarely occur in this species. The findings demonstrated that, under present experimental conditions, adult hamsters develop a broader spectrum of neoplasms than do prenatally exposed animals to identical precursors. The functional and developmental state of the organ at the time of exposure to carcinogenic stimuli and certain other factors were considered possible determinants influencing the development of some tumors.