Genetic background of resistance to cadmium-induced testicular toxicity in inbred Wistar-Imamichi rats.

We have previously reported that inbred Wistar-Imamichi (WI) rats are highly resistant to cadmium (Cd)-induced testicular toxicity compared with inbred Fischer 344 (F344) rats. The present study was to elucidate the genetic background of resistance to Cd-induced testicular toxicity in WI rats. The genetic analysis of susceptibility to Cd-induced testicular toxicity was conducted by using Cd-resistant WI and Cd-sensitive F344 strains as the parental rats and by using the testicular hemoglobin level as the indicator. In the frequency distribution of testicular hemoglobin levels in parental, first filial (F(1)) and second filial (F(2)) rats treated with Cd at a dose of 2.0 mg/kg, F(1) rats had testicular hemoglobin levels intermediate to WI and F344 rats, and F(2) rats segregated into three groups of low, intermediate, and high phenotypes at the expected ratio. Furthermore, the backcross progeny between WI and F(1) or between F344 and F(1) segregated into two groups with the expected ratio. Based on a simple Mendelian genetic analysis, these segregation patterns lead us to conclude that two codominant alleles at a gene locus are responsible for the susceptibility to Cd-induced testicular toxicity in rats. This is the first report for the genetic analysis of susceptibility to Cd-induced testicular toxicity in inbred rat strains.