INDUCTION OF SQUAMOUS-CELL CARCINOMAS IN THE SALIVARY-GLANDS OF RATS BY POTASSIUM-IODIDE

In a 2-year carcinogenicity study of potassium iodide (KI) in F344/DuC rj rats, squamous cell carcinomas (SCCs) were observed in the salivary glands of 4/40 males and 3/40 females receiving 1000 ppm KI in the dr inking water. Ductular proliferation with lobular atrophy was observed at high incidence in the submandibular glands of the high-dose animal s, and squamous metaplasia was frequently evident within the prolifera tive ductules and the larger interlobular ducts. A transition from met aplasia to SCC was apparent. The results suggest that squamous metapla sia in proliferative ductules, occurring secondarily to lobular impair ment induced by KI, may develop into SCCs via a non-genotoxic, prolife ration-dependent mechanism.