Metabolism of tirapazamine by multiple reductases in the nucleus11Abbreviations: TPZ, tirapazamine; P450 reductase, NADPH:cytochrome P450 reductase; PMSF, phenylmethylsulfonyl fluoride; DTT, dithiothreitol; DHR123, dihydrorhodamine 123; DAPI, 4′,6-diamidino-2-phenylindole, dihydrochloride; SN, supernatant from nuclei; LS, low salt; HS, high salt; and NM, nuclear matrix.