The Rates of the Exchange Reactions between [Gd(DTPA)] and the Endogenous Ions Cu2+ and Zn2+: A Kinetic Model for the Prediction of the In Vivo Stability of [Gd(DTPA)], Used as a Contrast Agent in Magnetic Resonance Imaging Export

@article{citeulike:3745973, abstract = {The kinetic stability of the complex [Gd(DTPA)]2- (H5DTPA=diethylenetriamine-N,N,Nprime,NPrime,NPrime-pentaacetic acid), used as a contrast-enhancing agent in magnetic resonance imaging (MRI), is characterised by the rates of the exchange reactions that take place with the endogenous ions Cu2+ and Zn2+. The reactions predominantly occur through the direct attack of Cu2+ and Zn2+ on the complex (rate constants are 0.93±0.17 M-1 s-1 and (5.6±0.4)×10-2 M-1 s-1, respectively). The proton-assisted dissociation of [Gd(DTPA)]2- is relatively slow (k1=0.58±0.22 M-1 s-1), and under physiological conditions the release of Gd3+ predominantly occurs through the reactions of the complex with the Cu2+ and Zn2+ ions. To interpret the rate data, the rate-controlling role of a dinuclear intermediate was assumed in which a glycinate fragment of DTPA is coordinated to Cu2+ or Zn2+. In the exchange reactions between [Gd(DTPA)]2- and Eu3+, smaller amounts of Cu2+ and Zn2+ and their complexes with the amino acids glycine and cysteine have a catalytic effect. In a model of the fate of the complex in the body fluids, the excretion and the ldquodissociationrdquo of [Gd(DTPA)]2- are regarded as parallel first-order processes, and by 10 h after the intravenous administration the ratio of the amounts of ldquodissociatedrdquo and excreted [Gd(DTPA)]2- is constant. From about this time, 1.71 \% of the injected dose of [Gd(DTPA)]2- is ldquodissociatedrdquo. The results of equilibrium calculations indicate that the Gd3+ released from the complex is in the form of Gd3+-citrate.}, address = {Department of Inorganic and Analytical Chemistry lajos Kossuth University, Debrecen 4010 (Hungary) Fax: (+36) 52-489667; Current address: Institute of Inorganic and Analytical Chemistry, University of Lausanne BCH, 1015 Lausanne (Switzerland)}, author = {Sarka, L. and Burai, L. and Br\"{u}cher, E.}, citeulike-article-id = {3745973}, citeulike-linkout-0 = {http://dx.doi.org/10.1002/(SICI)1521-3765(20000218)6:4%3C719::AID-CHEM719%3E3.0.CO;2-2}, citeulike-linkout-1 = {http://www3.interscience.wiley.com/cgi-bin/abstract/70001021/ABSTRACT}, doi = {10.1002/(SICI)1521-3765(20000218)6:4%3C719::AID-CHEM719%3E3.0.CO;2-2}, journal = {Chemistry - A European Journal}, keywords = {agents, chemistry, contrast, nmr}, number = {4}, pages = {719--724}, posted-at = {2008-12-04 11:54:35}, priority = {2}, title = {The Rates of the Exchange Reactions between [Gd(DTPA)] and the Endogenous Ions Cu2+ and Zn2+: A Kinetic Model for the Prediction of the In Vivo Stability of [Gd(DTPA)], Used as a Contrast Agent in Magnetic Resonance Imaging}, url = {http://dx.doi.org/10.1002/(SICI)1521-3765(20000218)6:4%3C719::AID-CHEM719%3E3.0.CO;2-2}, volume = {6}, year = {2000} }

TY - JOUR ID - citeulike:3745973 L3 - citeulike-article-id:3745973 N2 - The kinetic stability of the complex [Gd(DTPA)]2- (H5DTPA=diethylenetriamine-N,N,Nprime,NPrime,NPrime-pentaacetic acid), used as a contrast-enhancing agent in magnetic resonance imaging (MRI), is characterised by the rates of the exchange reactions that take place with the endogenous ions Cu2+ and Zn2+. The reactions predominantly occur through the direct attack of Cu2+ and Zn2+ on the complex (rate constants are 0.93±0.17 M-1 s-1 and (5.6±0.4)×10-2 M-1 s-1, respectively). The proton-assisted dissociation of [Gd(DTPA)]2- is relatively slow (k1=0.58±0.22 M-1 s-1), and under physiological conditions the release of Gd3+ predominantly occurs through the reactions of the complex with the Cu2+ and Zn2+ ions. To interpret the rate data, the rate-controlling role of a dinuclear intermediate was assumed in which a glycinate fragment of DTPA is coordinated to Cu2+ or Zn2+. In the exchange reactions between [Gd(DTPA)]2- and Eu3+, smaller amounts of Cu2+ and Zn2+ and their complexes with the amino acids glycine and cysteine have a catalytic effect. In a model of the fate of the complex in the body fluids, the excretion and the ldquodissociationrdquo of [Gd(DTPA)]2- are regarded as parallel first-order processes, and by 10 h after the intravenous administration the ratio of the amounts of ldquodissociatedrdquo and excreted [Gd(DTPA)]2- is constant. From about this time, 1.71 % of the injected dose of [Gd(DTPA)]2- is ldquodissociatedrdquo. The results of equilibrium calculations indicate that the Gd3+ released from the complex is in the form of Gd3+-citrate. IS - 4 JF - Chemistry - A European Journal AD - Department of Inorganic and Analytical Chemistry lajos Kossuth University, Debrecen 4010 (Hungary) Fax: (+36) 52-489667; Current address: Institute of Inorganic and Analytical Chemistry, University of Lausanne BCH, 1015 Lausanne (Switzerland) EP - 724 TI - The Rates of the Exchange Reactions between [Gd(DTPA)] and the Endogenous Ions Cu2+ and Zn2+: A Kinetic Model for the Prediction of the In Vivo Stability of [Gd(DTPA)], Used as a Contrast Agent in Magnetic Resonance Imaging VL - 6 SP - 719 KW - agents KW - chemistry KW - contrast KW - nmr AU - Sarka, L AU - Burai, L AU - Brücher, E PY - 2000/// UR - http://dx.doi.org/10.1002/(SICI)1521-3765(20000218)6:4%3C719::AID-CHEM719%3E3.0.CO;2-2 ER -