Production of malignant tumors in rats with radioactive phosphorus.

PROCEDURE AND RESULTS Neoplasms were observed in two experimental groups of rats, i.e., (a) animals surviving a single Luso dose of P32 (4.5 /tc. per gram of body weight), and (b) those surviving repeated injections of P32 (1.5 /uà ̈. per gram of body weight every 3 weeks) for a total dose of 9 or 12 ¡ic. per gram. Adult white male rats of the C. F. Wistar strain, which weighed about 150 gin. each, obtained from Carworth Farms, were used. Spontaneous bone tumors have not been observed among normal animals of this strain (1). The rats were kept in an air-conditioned unit permitting constant temperature and hu midity. Radioactive material was injected by the intraperitoneal route. Complete autopsies were performed on all rats which died or were sacrificed. In almost all animals routine microscopic sections of femur and verte bra were taken. X-rays were taken of the entire skeleton of most animals, usually at the time of death or sacrifice. For controls, x-rays were made of the skeleton