TmDOTP(5-) as a (23)Na shift reagent for the subcutaneously implanted 9L gliosarcoma in rats

The use of TmDOTP(5-) as an in vivo (23)Na NMR shift reagent (SR) for subcutaneously implanted 9L gliosarcoma was evaluated. TmDOTP(5-) produced a single sharp extracellular peak after about 50-60 min of infusion, and did not cause any changes in the (31)P resonance areas or chemical shifts, suggesting that the SR is homogeneously distributed in the extracellular space and does not alter tumor bioenergetic status. TmDOTP(5-) and CoEDTA(-) as extracellular space markers gave identical results for relative extracellular space (0.25 +/- 0.03 and 0.25 +/- 0.04, respectively) and intracellular Na(+) concentration (19.3 +/- 4.0 mM and 18.6 +/- 3.9 mM, respectively), indicating that the biodistribution of the SR is the same as the well-accepted extracellular space marker. The in vivo T(1) and T(2) relaxation times of intra- and extracellular Na(+) were also measured. Our results indicate that TmDOTP(5-) promises to be an effective shift reagent and extracellular space marker in the 9L gliosarcoma and perhaps other tumors. Magn Reson Med 45:436-442, 2001.