Comparative study on the effects of cyclophosphamide on yeast in vitro and in the host-mediated assay: DNA damage and biological response.

Cyclophosphamide (CP), whether applied in its chemically activated form as 4-hydroperoxy-cyclophosphamide (4-OOH-CP) in vitro or in the host-mediated assay (HMA) using rats, exhibits toxic and mutagenic effects on excision deficient yeast cells. The expression of these effects is examined during a prolonged postincubation in buffer and compared with the ability of activated CP to induce interstrand cross-links and DNA fragmentation. At comparable doses, we observed a close similarity of biological and biochemical effects in either test system.