Induction of testicular sarcomas in Fischer rats by intratesticular injection of nickel subsulfide

Nickel subsulfide (Ni3S2) was injected in various amounts into the testis of adult Fischer rats for the study of the acute and chronic effects of Ni3S2 on testicular cells. Rats given injections of 0.6 to 10 mg of Ni3S2 developed an immediate inflammatory response at the site of injection, followed by a delayed, slowly evolving coagulation necrosis of seminiferous tubules and interstitial cells. The extent of testicular necrosis was dose dependent, but at doses of 5 or 10 mg of Ni3S2 the rats invariably developed subtotal destruction of the testis. The testis became atrophic, without regeneration of seminiferous tubules. No damage was seen in the other testis, and no systemic effects were noted. Malignant testicular neoplasms developed in 16 of 19 rats within 20 months after an injection of 10 mg of Ni3S2. These neoplasms were classified by light and electron microscopy as fibrosarcomas, malignant fibrous histiocytomas, and rhabdomyosarcomas. None of the testicular neoplasms was derived from germ cells or genital cord cells. The occurrence of rhabdomyosarcomas in the testis, an organ normally devoid of striated muscle, suggests that Ni3S2 induces malignant transformation of undifferentiated, pluripotential mesenchymal cells.

Carcinogenicity of nickel subsulfide in Fischer rats and Syrian hamsters after administration by various routes

In an endeavor to expand the variety of experimental models for study of nickel carcinogenesis, nickel subsulfide (Ni3S2) was administered to rodents by five previously untested routes. In two groups of Syrian hamsters, Ni3S2 induced multiple sarcomas at the sites of single im injections (5 or 10 mg of Ni3S2). In contrast, Ni3S2 did not induce any malignant tumors of the cheek pouches, oral cavity or gastrointestinal tract, despite multiple local applications to the cheek pouches of several groups of hamsters in total dosages as large as 1.1 g of Ni3S2. In a group of Fischer rats, single intratesticular injections of Ni3S2 (10 mg) induced many testicular sarcomas. In contrast, no malignant tumors developed in two groups of rats that received single injections into the submaxillary gland (2.5 mg of Ni3S2) or into the liver (5 mg of Ni3S2 via the portal venous system).