Chemical instability and methods for measurement of cisplatin adducts formed by interactions with cysteine and glutathione

Reactions between cisplatin or its aquated species and L-cysteine (L-cys) o r glutathione (GSH) were studied in vitro using liquid chromatography on-li ne with inductively coupled plasma mass spectrometry (LC-ICPMS) and/or elec trospray ionization mass spectrometry (LC-MS) in order to obtain informatio n on the mechanisms occurring in treated patients. Reaction between cisplat in and L-cys yielded initially 4 adducts of which only 2 were stable and de tectable after 24 hours incubation; their structures corresponded to bis-pl atinum cysteinyl adducts. Reaction of cisplatin with GSH proceeded via the formation of at least I I glutathione-platinum adducts (G1 - G11) which und erwent parallel reactions within 24 hours of incubation, probably to form h igher molecular weight species. Of the I I adducts, only 2, G3 and G7, whos e structures correspond to [Pt(NH3)(2)Cl](2)(SG) and [Pt(NH3)(2)OH](2)(SG) were still present in the reaction mixture after 24 hours incubation. This study shows that GSH, and to a lesser extent L-cys, incubated with cisplati n in vitro forms unstable and reactive platinum compounds and that LC-ICPMS and LC-MS are 2 complementary techniques suitable for the study of organom etallic compounds.