Induction of 8-azaguanine- and ouabain-resistant mutants by cyclophosphamide and 1-(pyridyl-3)-3,3-dimethyltriazene in Chinese hamster cells cultured in diffusion chambers in mice.

A host-mediated assay is described for induction of 8-azaguanine-resistant (azgr) and ouabain-resistant (ouar) mutants in Chinese hamster V79 cells cultured in diffusion chambers (DC) in C3H mice. Injection of the hosts with the indirect mutagen/carcinogen cyclophosphamide (CPP) or 1-(pyridyl-3)-3,3-dimethyltriazene (PyDT) caused a dose-dependent increase in mutation frequency at the loci of azgr and ouar in the V79 target cells. Plating efficiency of V79 cells in DC in mice was decreased depending upon the dose of CPP or PyDT given to the hosts. In addition, the relationship between expression time and mutation frequency was examined and discussed. The data support the use of this system as an effective screening procedure for suspected environmental mutagens or carcinogens, especially those that need to be metabolically activated in vivo.