Calcium binding by gadolinium-based MR contrast agents

PURPOSE: This study was conducted to characterize the alterations in ionic sodium, potassium, and calcium by gadolinium-based MR contrast agents. MATERIALS AND METHODS: An electrolyte solution (ES) containing 1.2 mM/L calcium ions,120 mM/L sodium, and 4.0 mM/L potassium were diluted with various gadolinium compounds and alterations in ionized electrolytes were measured using an ion-specific electrometer. Gadolinium compounds including Gd-DTPA, Gd-DOTA, gadoteridol, gadodiamide, meglumine/sodium diatrizoate (76% Urografin), and isotonic saline as a control were investigated. The dilution ranged from 5% (ES/test solution = 100/5) to 100%. Alterations of ionic electrolytes were measured. Calcium-binding capacities caused by each gadolinium compound also were measured. RESULTS: The alterations of ionic sodium and potassium by gadolinium compound were similar to those of isotonic saline. A significant reduction in ionized calcium was observed with Gd-DTPA and Gd-DOTA in comparison with gadoteridol and gadodiamide. CONCLUSION: Ionic gadolinium compounds induced significant reductions of calcium ions in vitro compared with non-ionic gadolinium compounds.