OXAZOLIDONYLETHYL ADDUCTS TO HEMOGLOBIN AND DNA FOLLOWING NORNITROGENMUSTARD EXPOSURE

Formation of adducts to hemoglobin (Hb) and DNA of nornitrogen mustard (NNM) was studied with the aim of developing a method for monitoring exposure to NNM. Adducts to N-terminal valines in Hb were studied by t he N-alkyl Edman method using pentafluorophenyl isothiocyanate (PFPITC ) as the derivatizing reagent. In preliminary studies five major Hb ad ducts were shown to be formed in reaction of NNM with red cell hemolys ate in vitro. Following treatment with PFPITC three of these were foun d to be pentafluorophenylthiohydantoins (PFPTHs) of N-alkylated valine s and the fourth probably originates from NNM esters in which PFPITC h ad reacted with the nitrogen of N-chloroethylaminoethyl. A PFPTH was f ound to originate from N-2-(3-oxazolidonyl)ethylvaline, Val-OZ. Val-OZ is formed in reaction, with ring closure to oxazolidone, of CO2 with the 2-chloroethylamino group in the primary valine-N adduct. Besides a few other adducts, Val-OZ was also observed in mouse Hb following inj ection of NNM, and also after injection of cyclophosphamide. Following reaction in vitro of NNM with DNA, three major adducts to guanine-N-7 were observed; one of them, 7-[N'-(2-chloroethyl)-2-aminoethyl]-guani ne (NNMCI), was converted by carbonate to 7-[2-(3-oxazolidonyl)ethyl]g uanine (Gua-OZ). In mice treated with NNM, Gua-OZ was the only DNA add uct observed. Val-OZ is a chemically stable Hb adduct, potentially use ful for monitoring exposures to NNM and cyclophosphamide.