Chronic carcinogenic and toxic effects of a single subcutaneous dose of cadmium in the male Fischer rat.

The carcinogenic effects of cadmium have not been thoroughly assessed in the commonly used Fischer (F344) rat. This study determined tumor incidence in various tissues of male F344/NCr rats after a single dose of cadmium. Cadmium (as CdCl2) was given sc in the dorsal thoracic midline at 30 mumole/kg to 70 8-week old male F344 rats while controls (n = 50) received saline. Rats were observed during the next 90 weeks. Early deaths (less than or equal to 32 weeks), due mostly to acute cadmium-induced hepatotoxicity, accounted for 37 of the cadmium-treated rats while no control rats died in the same period. A high incidence of injection site sarcomas (ISS) occurred in the cadmium-treated group (21 ISS/32 rats at risk; 66%) while only 1/50 occurred in controls (2%). In fact, ISS were the major cause of morbidity after 35 weeks in cadmium-treated rats. These tumors were mostly fibrosarcomas, although histiocytic and osteogenic sarcomas also occurred. Testicular interstitial cell tumors, which show a very high spontaneous incidence in this strain (41/49; 84%), were not markedly affected by cadmium (30/31; 97%). This is in sharp contrast to other strains, such as the Wistar, in which cadmium treatment is reported to cause as much as an eightfold increase in interstitial cell (Leydig cell) tumor incidence. The incidence of large granular lymphocyte (LGL) leukemia, which also occurred frequently in control F344 rats (12/47; 26%) was markedly decreased (2/31; 7%) by cadmium. Our recent studies indicate acute lymphonecrotic effects occur with cadmium in lymphoid tissues of rats, and this may be related to the suppression of the leukemia. These results indicate that cadmium is very effective in inducing ISS in F344 rats, as is the case with other strains thus far tested, and also markedly reduces spontaneous leukemia incidence.