title: 31P nuclear magnetic resonance spectroscopic observation of the intracellular transformations of oncostatic cyclophosphamide metabolites.
abstract: 31P NMR spectroscopy was used to directly monitor, for the first time, the intracellular chemistry of the ultimate active metabolite of cyclophosphamide, namely, phosphoramide mustard. These NMR studies utilized a human histiocytic lymphoma cell line (U937), embedded in agarose gel threads, and perfused with medium containing synthetically derived metabolites (4-hydroxycyclophosphamide, aldophosphamide, and phosphoramide mustard). Metabolites 2 or 3 or both readily crossed the cell membrane; in contrast, the membrane was relatively impermeable to 4. Intracellular concentrations of 4 could, therefore, be attributed primarily to the intracellular fragmentation of 3. Signals suggestive of either carboxyphosphamide or 4-ketophosphamide were not detected. Spectral data were used to calculate a rate constant of (5.4 +/- 0.3) X 10(-3) min-1 for the intracellular disappearance of 4 at 23 degrees C. The intracellular pH was determined to be 7.1 from the chemical shift of the internal inorganic phosphate signal.
mesh_terms: D001711:Biotransformation; D002460:Cell Line; D003520:Cyclophosphamide / Q000031:analogs & derivatives* / Q000378:metabolism*; D006801:Humans; D016403:Lymphoma, Large B-Cell, Diffuse; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013329:Structure-Activity Relationship
chemical_list: D003520:Cyclophosphamide