There was no significant difference in the incidence of tumors between newborn and adult hamsters receiving a single administration of cycasin and between adult hamsters

Three groups of newborn hamsters received a single s.c. injection of 0.2, 0.4, and 0.6 rug cycasin/g body weight within 24 hr after birth. Two groups of adult hamsters each received one dose of 0.1 or 0.15 rug cycasin/g body weight by stomach tube. Another three groups of adult hamsters received two to four doses of 0.1 rug cycasin/g body weight by stomach tube at intervals of 1 month. There was no significant difference in the incidence of tumors between newborn and adult hamsters receiving a single administration of cycasin and between adult hamsters receiving single and repeated administrations. However, adult hamsters receiving the larger single dose of cycasin showed a higher incidence of tumors than those receiving the smaller single dose. The most important changes induced in hamsters with cycasin were seen in the liver and consisted of proliferative changes of the intrahepatic bile ducts. Bile duct carcinomas were produced both in newborn and adult hamsters. Although hepatocellular carcinomas are as readily induced as bile duct carcinomas in newborn hamsters, hepatocellular carcinomas were not found among adult animals. Eight liver tumors induced by bycasin were transplanted, and five transplantable tumor lines were successfully established. Four lines originated in intrahepatic bile duct carcinomas, and the fifth originated in an anaplastic carcinoma, presumably of liver cell origin. Kidney and intestinal tumors, which were frequently induced in rats by cycasin, were observed in a much lower incidence in hamsters.