Related Experiment Videos
Action of gadolinium complexes on different enzyme systems.
M Allard1, J M Caillé, B Bonnemain
1Department of Neuroradiology, Groupe Hospitalier Pellegrin-Tripode, Bordeaux, France.
Acta Radiologica. Supplementum
|January 1, 1986
Summary
Gadolinium contrast agents for MRI show low toxicity and good signal properties. This study found that while ionic gadolinium and chelators inhibit glutamate decarboxylase (GAD), gadolinium complexes do not affect GAD or cholineacetyl transferase (ChAT) activity.
Area of Science:
- Neuroscience
- Radiology
- Biochemistry
Background:
- Gadolinium complexes are vital MRI contrast agents due to low toxicity and adequate paramagnetic properties.
- Investigating the impact of MRI contrast media on brain enzyme activity is crucial for understanding potential neurotoxicity.
- Glutamate decarboxylase (GAD) and cholineacetyl transferase (ChAT) are key enzymes in neurotransmitter synthesis within the brain.
Purpose of the Study:
- To evaluate the effects of various gadolinium-based contrast agents and their components on the activity of GAD and ChAT in rat striatum homogenates.
- To determine if gadolinium complexes exhibit differential effects on calcium-dependent (GAD) versus calcium-independent (ChAT) enzymes.
- To assess the safety profile of gadolinium complexes as MRI contrast media concerning specific enzymatic activities.
Main Methods:
- Enzyme activity assays were performed on rat striatum homogenates.
- Variable concentrations (10⁻² to 10⁻⁹ mol/l) of gadolinium sulphate, EDTA, DTPA, DOTA, Gd-EDTA, Gd-DTPA, and Gd-DOTA were used.
- The activity of glutamate decarboxylase (GAD) and cholineacetyl transferase (ChAT) was measured in the presence of these agents.
Main Results:
- Ionic gadolinium and chelating agents (EDTA, DTPA, DOTA) inhibited glutamate decarboxylase (GAD) activity.
- Gadolinium complexes (Gd-EDTA, Gd-DTPA, Gd-DOTA) showed a mild inhibition (approx. 15%) of GAD activity.
- Neither ionic gadolinium, chelators, nor gadolinium complexes affected the activity of cholineacetyl transferase (ChAT).
Conclusions:
- Gadolinium complexes demonstrate a reduced inhibitory effect on GAD compared to ionic gadolinium and chelators.
- Cholineacetyl transferase (ChAT) activity remains unaffected by all tested gadolinium compounds, suggesting enzyme-specific interactions.
- Gadolinium complexes maintain paramagnetic properties for MRI while exhibiting a more favorable enzymatic safety profile than their ionic or chelator forms.