Development of thymic lymphomas by oral administration of N-nitroso-N-propylurea and establishment of transplantable lines of thymic lymphoma in F344 rats.

Forty-eight female F344/DuCrj rats were given a 400-ppm solution of N-nitroso-N-propylurea (CAS: 816-57-9) continuously in their drinking water. Thymic lymphomas were induced most frequently (85%) followed by duodenal tumors (48%). Sixteen tumors were examined by the immunofluorescence inhibition test for murine leukemia virus-related antigens; 15 were negative and the other was weakly positive. Twenty-six tumors were intraperitoneally and subcutaneously transplanted syngeneically; 25 (96%) were successfully transplanted intraperitoneally and 24 (92%) subcutaneously. The serial intraperitoneal transplantation was continued, and 22 lines of transplantable lymphoma in an ascites form were established. In almost all tumor lines, tumor cells took in a high percentage of recipient rats and caused the death of the recipients within 12-23 days. The thymus, liver, spleen, greater omentum, and lymph nodes were frequently invaded by transplanted tumor cells. The tumor lines were considered to be of T-cell lineage.