Development of biliary and hepatic neoplasms in guinea pigs treated with N-nitrosobis(2-oxopropyl)amine.

N-Nitrosobis(2-oxopropyl)amine (BOP) was administered subcutaneously to 29 male inbred strain 13 guinea pigs at weekly intervals for 4 weeks. The guinea pigs were observed until their death or termination of the experiment at the end of 55 weeks. Of 14 guinea pigs that survived more than 30 weeks, 7 animals developed cholangiocarcinomas and 2 developed hepatocellular carcinomas. Tumors of other sites were not found.