31P Nuclear Magnetic Resonanse Spectroscopic Observation of the Intracellular Transformations of Oncostatic Cyclophosphamide Metabolites

Article abstract of DOI:10.1021/jm00157a015

(31)P 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 (2), aldophosphamide (3), and phosphoramide mustard (4)).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) * 10^-3 min^-1 for the intracellular disappearance of 4 at 23 deg C.The intracellular pH was determined to be 7.1 from the chemical shift of the internal inorganic phosphate signal.