Tissue culture cytotoxicity assay for cyclophosphamide metabolites in rat body fluids.

An in vitro cytotoxicity assay for cyclophosphamide metabolites in rat body fluids is described. Of the two tissue culture tumor cell lines employed, the Walker-256 rat carcinosarcoma was more sensitive to metabolite levels than the L-1210 mouse lymphocytic leukemia. The Walker-256 system detected cyclophosphamide metabolite levels two orders of magnitude lower than the commonly used 4-(p-nitrobenzyl)pyridine analytical procedure.