31P and 23Na NMR studies of the structure and lability of the sodium shift reagent, bis(tripolyphosphate)dysprosium(III) ([Dy(P3O10)]7-) ion, and its decomposition in the presence of rat muscle.

The 31P NMR of aqueous [Dy(P3O10)2]7- demonstrates that it is in slow exchange with P3O5-10 on the NMR time scale. In the presence of tissue, [Dy(P3O10)2]7- decomposes to PO4 with an accompanying slow change of the tissue 23Na NMR of extracellular Na+ ion in several NMR distinguishable extracellular sites.