RELAXOMETRY, LUMINESCENCE MEASUREMENTS, ELECTROPHORESIS, AND ANIMAL BIODISTRIBUTION OF LANTHANIDE(III) COMPLEXES OF SOME POLYAZA MACROCYCLIC ACETATES CONTAINING PYRIDINE
Wd. Kim et al., RELAXOMETRY, LUMINESCENCE MEASUREMENTS, ELECTROPHORESIS, AND ANIMAL BIODISTRIBUTION OF LANTHANIDE(III) COMPLEXES OF SOME POLYAZA MACROCYCLIC ACETATES CONTAINING PYRIDINE, Inorganic chemistry, 34(8), 1995, pp. 2233-2243
Four Gd3+ complexes [Gd(BP2A)(+), Gd(PC2A)(+), Gd(PCTA)(0), and Gd(BPO
4A)(-)] with polyazamacrocyclic ligands that contain a pyridine moiety
were prepared and examined for possible use as MRI contrast enhanceme
nt agents. We estimated the number of inner sphere water molecules (q(
Gd)) for the Gd3+ complexes from the values of q found for the Tb3+ an
d/or Eu3+ complexes by luminescence lifetime measurements. We have est
imated that q(Gd) = 3.5, 3.3, 2.4, and 0.2 for Gd(BP2A)(+), Gd(PC2A)(), Gd(PCTP)(0), and Gd(BPO4A)(-), respectively. The inner sphere relax
ivities (r(1,inner)) of these tetraaza macrocyclic complexes were high
er than that of Gd(DOTA)(-) [i.e. 6.79 for Gd(BP2A)(+), 6.21 for Gd(PC
2A)(+), and 4.60 for Gd(PCTA)(0) mM(-1)s(-1) at 40 MHz and 25 degrees
C], but the normalized relaxivities per q(Gd) (1.94, 1.88, and 1.92 mM
(-1) s(-1), respectively) were comparable to that of Gd(DOTA)(-). A qu
antitative treatment of the NMRD profiles based on Solomon-Bloembergen
-Morgan theory, using the NMRD profile of Gd(BPO4A)(-) to correct for
an outer sphere contribution, showed that the complexes exhibit charac
teristics similar to that of GP(DOTA)(-) but with shorter electronic r
elaxation times. Tissue biodistribution results using radioactive Sm-1
53 and Gd-159 complexes in rats indicate that the cationic [Sm-153(BP2
A)(+) and Sm-153(PC2A)(+)] complexes accumulate preferably in the bone
tissue while the neutral [Sm-153(PCTA)(0)] and anionic [Sm-153(BPO4A)
-] complexes appear to have renal clearances similar to those of other
low molecular weight contrast agents [i.e. Gd(DTPA)(2-) and Gd(DOTA)(
-)].