STUDIES ON THE FORMATION OF REACTIVE INTERMEDIATES FROM THE ANTINEOPLASTIC AGENT N,N'-BIS(2-CHLOROETHYL)-N-NITROSOUREA (BCNU) IN-VITRO AND IN-VIVO - CHARACTERIZATION OF NOVEL GLUTATHIONE ADDUCTS BY IONSPRAY TANDEM MASS-SPECTROMETRY

In a study designed to examine the nature of short-lived, electrophili c intermediates liberated during decomposition of N,N'-bis(2-chloroeth yl)-N-nitrosourea (BCNU) in vitro and also on administration of BCNU ( 140 mu mol i.p.) to rats in who, both on-line and off-line LC/MS/MS te chniques were employed to detect and characterize the corresponding gl utathione (GSH) adducts present in incubation media and excreted into bite, respectively, In vitro, four GSH conjugates were formed and thes e were identified, on the basis of their product ion spectra, as produ cts of S- and N-carbamoylation and alkylation reactions, Although the relative proportions of these in vitro adducts were found to depend on the molar ratios of GSH and BCNU, the major adduct under all conditio ns studied proved to be S-2-chloroethytcarbamoyl)glutathione (SCG), An alysis of untreated bile samples by means of on-line LC/MS/MS with con stant neutral loss (129 u) and precursor ion (m/z 179) scanning techni ques again led to the detection of four GSH conjugates, although only one of these (SCG) was common to the group of adducts identified in vi tro. All of the GSH conjugates detected in bile represented products o f S-carbamoylation, indicating that the alkylating moiety released fro m BCNU undergoes reactions in vivo with nucleophiles other than GSH.