31p nuclear magnetic resonance of platelet dense granule adenine nucleotides

31P-NMR spectra of platelets were obtained after depletion of metabolic ATP and ADP by inhibitors. The remaining dense-granule nucleotides show prominent NMR peaks for rabbit, cow and pig, but not human, platelets. Each animal species has a unique and reproducible spectrum reflecting differences in dense-granule compositions, but in all, the dense-granule peaks are broader (by as much as 10-fold) than in spectra of solutions approximating the granule composition. Measurement of the transverse relaxation times, T2, for each resonance band yields intrinsic peak widths which generally are much narrower than observed peak widths. This result indicates that the broad dense-granule peaks are composed of intrinsically narrower peaks of slightly different chemical shifts, implying that the platelet dense granules of a given species are heterogeneous in composition. Our observations suggest that variations in divalent cation ratios and/or pH in the dense granules of a single animal can explain the spread of resonance positions.