Intranuclear Inclusions and Neoplasms in the Kidneys of Wild Rats2

Abstract

Nuclear inclusions have been found in kidneys of nearly 100 percent of seemingly healthy, adult wild rats (Rattus norvegicus) captured on refuse dumps in the vicinity of Hanover, New Hampshire. In spite of the viral-like appearance of the inclusions, repeated attempts at isolation of virus were unsuccessful. A number of other investigations indicated that lead was the probable etiologic agent. To test this hypothesis, intranuclear inclusions were induced in the kidneys of albino rats by lead acetate and these inclusions had the same peculiarities, both histochemically and electron microscopically, as those in the wild rats. Assays of wildrat tissues revealed abnormal content of lead and suggested that these animals had chronic lead poisoning. The nuclear inclusions appeared to be associated with development of renal neoplasms ranging from circumscribed tumors to invasive, metastasizing carcinomas. The source of the lead inducing these changes has not been determined. Field observations have suggested that rat populations living and feeding on burning refuse dumps have a fairly constant exposure to leadcontaining fumes.