title: Cationic drug analysis using matrix-assisted laser desorption/ionization mass spectrometry: application to influx kinetics, multidrug resistance, and intracellular chemical change.
abstract: Highly sensitive and convenient analysis of intracellular cationic drugs has been achieved by applying matrix-assisted laser desorption/ionization mass spectrometry (MALD-MS). Tetraphenylphosphonium cation was readily identified and quantified (using methyltriphenylphosphonium cation as an internal standard) at subpicomole levels in crude lysate from < 4 x 10(3) FaDu human hypopharyngeal carcinoma cells. A quantitative MALD-MS time course for tetraphenylphosphonium cation accumulation into FaDu cells was comparable to a time course using scintillation counting with tritiated tetraphenylphosphonium. MALD-MS was also capable of demonstrating the reduced accumulation of the cationic drug rhodamine-123 by DoxR MCF7, a multiply drug-resistant human breast adenocarcinoma cell line, relative to the nonresistant parent line MCF7. In addition, MALD-MS was used to follow a chemical reaction inside intact FaDu cells: the formation of a hydrazone (II-51) from benzaldehyde and an acylhydrazide, 5-[tris(4-dimethylaminophenyl)phosphonio]pentanoyl hydrazide (II-25). These results suggest that MALD-MS may provide a rapid and practical alternative to existing methods for the analysis of cationic drugs, toxins, and their metabolites in cells and tissues.
authors.affiliation: Department of Chemistry, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: D
authors.initials: D
authors.lastname: Rideout
authors.forename: A
authors.initials: A
authors.lastname: Bustamante
authors.forename: G
authors.initials: G
authors.lastname: Siuzdak
mesh_terms: D000230:Adenocarcinoma; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D001692:Biological Transport; D001943:Breast Neoplasms; D002294:Carcinoma, Squamous Cell; D002412:Cations; D002460:Cell Line; D004317:Doxorubicin / Q000633:toxicity; D004351:Drug Resistance / Q000502:physiology*; D005260:Female; D006801:Humans; D007012:Hypopharyngeal Neoplasms; D007700:Kinetics; D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods; D015394:Molecular Structure; D009861:Onium Compounds / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D013329:Structure-Activity Relationship; D014320:Triphenylmethyl Compounds / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D014407:Tumor Cells, Cultured
chemical_list: D001547:Benzaldehydes; D002412:Cations; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D004317:Doxorubicin; C032175:benzaldehyde; C013289:tetraphenylphosphonium