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

Nickel sarcomatogenesis induced by a single intramuscular injection of 10 m g of nickel subsulfide (NiSS) into the soft tissue of two different colonie s of Wistar rats was studied. In spontaneously hypertensive rats (SHR), a s pecific inbred colony of rats derived from a certain Wister strain, the sar coma 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%) i n the CWR group (15 female and 16 male) (P < 0.005). The incidence of sarco ma induction was lower in female rats than in male rats in both the SHR (fe male 13.3% < male 33.3%) and CWR (female 53.3% < male 81.4%) groups, Primar y tumors in the SHR group exhibited a lower grade of metastasis to lymph no des (P < 0.001) and lungs (P < 0.05) than in the CWR group. Our study demon strated that rats in a certain specific inbred colony are less susceptible to nickel tumorigenesis in soft tissue than rats in a common closed colony. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.