Morphologic character of transforming renal cell cultures derived from Wistar rats given dimethylnitrosamine

The morphologic character of kidney cells during serial subculture following isolation from Wistar rats treated several hours to 1 week previously with a carcinogenic dose of dimethylnitrosamine (DMN; 60 mg/kg body weight following protein deprivation) was compared with the appearance of cultures derived from normal control rats. Apart from early signs of cell toxicity, cultures from DMN-treated rats appeared similar to those from untreated rats for the first four passages. Control cells underwent senescence usually by subculture 4, whereas the test cultures survived to express morphologic transformation (usually at subculture 5) as dense macroscopic colonies of piled up cells. In 18 of the 20 test cultures, the cell populations that persisted in continuous culture following expression of morphologic transformation were exclusively mesenchymal, closely resembling DMN-induced renal mesenchymal tumor cells in continuous culture. In the remaining 2 test cultures from DMN-treated rats, a persisting population of abnormal epithelium was present in addition to morphologically transformed mesenchymal cells. The occurrence of populations of altered mesenchymal and epithelial cells characterized by prolonged survival in vitro following isolation from rats shortly after treatment with a carcinogenic dose of DMN was believed to be related to the long-term induction in the rat kidney of a high incidence of mesenchymal tumors and a lower incidence of cortical epithelial tumors by the same dose schedule.