Low susceptibility of specific inbred colonies of rats to nickel tumorigenesis in soft tissue

Nickel sarcomatogenesis induced by a single intramuscular injection of 10 mg of nickel subsulfide (NiSS) into the soft tissue of two different colonies of Wistar rats was studied. In spontaneously hypertensive rats (SHR), a specific inbred colony of rats derived from a certain Wistar strain, the sarcoma induction rate was lower than that in common closed colony rats of the same strain (CWR). Sarcomas were induced in only 7 of the 30 rats (23.3%) in the SHR group (15 female and 15 male) but in 21 of the 31 rats (67.7%) in the CWR group (15 female and 16 male) (P<0.005). The incidence of sarcoma induction was lower in female rats than in male rats in both the SHR (female 13.3%<male 33.3%) and CWR (female 53.3%<male 81.4%) groups. Primary tumors in the SHR group exhibited a lower grade of metastasis to lymph nodes (P<0.001) and lungs (P<0.05) than in the CWR group. Our study demonstrated that rats in a certain specific inbred colony are less susceptible to nickel tumorigenesis in soft tissue than rats in a common closed colony.