Related Experiment Video
Updated: Aug 11, 2026

Human In Vitro Suppression as Screening Tool for the Recognition of an Early State of Immune Imbalance
Published on: July 22, 2011
Species dependence on plasma protein binding and relaxivity of the gadolinium-based MRI contrast agent MS-325
Harriet B Eldredge1, Marga Spiller, Jaclyn M Chasse
1EPIX Pharmaceuticals, Cambridge, Massachusetts. 02142-1118, USA.
Rationale And Objectives:
We sought to determine whether there is a species dependence on plasma protein and serum album binding and/or relaxivity of the MR contrast agent MS-325.
Methods:
Equilibrium binding of MS-325 to plasma proteins or purified serum albumin was determined as a function of chelate concentration. T1 and T2 values were determined at 0.47 and 1.41 T, and NMRD profiles were measured to determine the changes in relaxivity over varying field strengths from 0.002 to 1.2 T.
Results:
The binding of MS-325 to either animal plasma or serum albumin plateaus at chelate concentrations less than 0.1 mM with human, pig, and rabbit plasmas showing maximum binding. Human and pig plasmas show the greatest observed relaxivity enhancement in the presence of MS-325.
Conclusions:
MS-325 exhibits increased relaxivity in blood plasma as the result of plasma protein binding. Binding ranged from 64% to 91% and was species dependent: human > pig approximately rabbit > dog approximately rat approximately mouse.
Related Concept Videos
Magnetic Resonance Imaging
Imaging Studies I: CT and MRI
Description of the Procedures
Computed Tomography (CT) scan:
Computed Tomography (CT) scans use X-ray technology to generate detailed images of bones, organs, and tissues. During the scan, the patient lies on a moving table...
Factors Affecting Protein-Drug Binding: Protein-Related Factors
The physicochemical properties of a drug play a significant role in its ability to bind to proteins. Lipophilic drugs, which dissolve in fats, oils, and lipids, can be bound by...
Imaging Studies for Cardiovascular System IV: CMRI
Factors Affecting Protein-Drug Binding: Drug-Related Factors
One crucial factor in drug-protein binding is the drug's lipophilicity or its affinity for fat. More lipophilic drugs tend to have higher binding extents. For example, highly lipophilic drugs like cloxacillin exhibit substantial protein binding, with as much as 95% of the drug binding to proteins. In contrast,...

