the anionic frequency shift reagent , dysprosium ( iii ) tripolyphosphate , which does not permeate intact cells , when added to suspensions of intact adult rat cardiac myocytes , alters the nmr frequency of extracellular sodium ions , [ na+ ] o , leaving that of intracellular ions , [ na+ ] i , unaffected .
C0003075
anionic
C0022023
ions