HIGH SUSCEPTIBILITY OF SPECIFIC INBRED COLONIES OF RATS TO N-2-FLUORENYLACETAMIDE-INDUCED HEPATOCARCINOGENESIS

N-2-Fluorenylacetamide (FAA)-induced hepatocarcinogenesis in three colonies of Wistar-strain rats was studied. Two specific inbred colonies of rats derived from a Wistar strain, normotensive rats of Wistar Kyoto colony (WKY) and spontaneously hypertensive rats separated from WKY(SHR), showed higher inductions of preneoplastic altered foci of basophilic cell type and hepatocellular carcinomas as compared to common closed colony rats of the same strain (CWR). After 7 weeks of 0.02% FAA-containing diet, preneoplastic foci in WKY were found 4.8 times more frequently and in SHR 2.5 times more frequently than in CWR. Most of the foci found in WKY (92.5% of the total number of foci) and in SHR (87.1%) were of basophilic cell type, whereas most of the foci in CWR (71.3%) were acidophilic. After 7 months of the diet, multiple hepatocellular carcinomas were found in most rats in WKY (87.5% of the total number of rats, 2.6/rat) and SHR (81.8%, 2.5/rat) as compared to CWR (14.3%, 0.14/rat). These data demonstrate that rats in specific inbred colonies possess even higher susceptibility to FAA than CWR, and the susceptibility is closely related to the higher incidence of basophilic foci.