Tumor Induction by Repeated Injections of Urethan in Newborn and Adult Hamsters: Age Influence. II

Summary

Ten subcutaneous injections of 1 mg urethan per g body weight were administered weekly to Syrian golden hamsters at birth and adult age. Significantly higher numbers of forestomach papillomas developed in animals that began to receive urethan at adulthood than at birth, even though there were similar incidences in animals having this lesion in both age groups. On the other hand, appreciably more intestinal tumors were found in those hamsters starting to receive the treatment as newborns than as adults. In addition, dermal melanocytomas and thyroid, lung, and some other tissue tumors were induced without any apparent difference in incidences in the two age groups. In contrast to the effect of a single carcinogenic dose to which only two tissues responded, several additional tissues developed tumors when challenged by repeated injections of urethan. Either their tumorigenic threshold dose was higher and they needed periodic stimuli, or morphologic and functional development was not at an appropriate stage for tumor induction at the time of the single injection. The possible effect that the age of the host has on tumorigenesis is discussed in light of the results obtained.