Carcinogenic action of nickel and cadmium powders in the same rat

Abstract

Powders of nickel and cadmium metals were compared for their relative carcinogenic action when injected in contra thigh muscles of legs in the same Fischer-344 rat. For negative controls, rats of both sexes were injected im with 0.2 mL of the suspending vehicle, trioctanoin, once a month for 12 m. The two positive controls were treated once a month with either a suspension of powdered nickel (10 mg/mL for 5 m) or powdered cadmium (5 mg/mL twice). These dose levels were those found previously in the authors' laboratories to yield fibrosarcomas in 50–70% of the treated animals. For the combined experiment where the animals were injected with Ni and Cd in contra legs, the doses were about one-half of that used for the positive controls. Individual vehicle controls were used for each group. The fibrosarcoma yields for the experiments with individual positive metal controls were: vehicle alone, 0%; for both nickel and cadmium injected individually, between 60 and 80% for both males and females. In the combined metal experiment, one male and one female vehicle control developed tumors at the site of injection. The yield in the nickel leg was 14% for the females and 57% for the males; in the cadmium leg, the values were 93 and 50%, respectively. Only one male and one female developed sarcomas in both legs; in each case, the cadmium-induced tumor appeared first and grew seven to eight times larger than that induced by nickel.