Genetic Controls of Susceptibility and Resistance to 4‐Nitroquinoline 1‐Oxide‐induced Tongue Carcinomas in Rats

We analyzed the incidence of infiltrative mass‐type tongue carcinomas (IMTC) induced in 550 rats by continuous oral administration of 0.001% 4‐nitroquinoline 1‐oxide solution for 180 days. The study included various crosses of susceptible Dark‐Agouti rats (DA) and resistant Wistar/Furth rats (WF). DA showed a 93.6% incidence of IMTC measuring more than 5 mm in their largest diameter, while WF showed only a 4% incidence. Reciprocal F(1) and F(2) hybrids mated by DA and WF showed 47.5% and 45.8% incidences, respectively. Meanwhile, reciprocal backcrossed hybrids to DA and WF showed 73.7%, and 24.6% incidences, respectively. Segregation of the incidences suggests that there are two autosomal dominant genes, one linked to the susceptibility of DA and the other to the resistance of WF.