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Human monoamine oxidase. Lack of brain and platelet correlation
Abstract:
Monoamine oxidase (MAO) exists in two forms, MAO A and MAO B. Both are present in human brain, but the human platelet contains only MAO B. We studied whether individual variations in the activity of human platelet MAO B reflect individual variations in cerebral cortical MAO activities. Optimal conditions were determined for the measurement of MAO activities in both the platelet and cerebral cortex, obtained from 14 patients with epilepsy during clinically indicated neurosurgery. There was no significant correlation between the activities of MAO B in the cerebral cortex and platelets of these patients. Platelet MAO B activities also failed to correlate significantly with cerebral cortical MAO A activities. However, there was a significant positive correlation between cerebral cortical MAO A and MAO B activities. Individual variations in platelet MAO B activities do not reflect individual variations in either cerebral cortical MAO B or MAO A activities in patients with epilepsy who undergo neurosurgery.
Insights
Individual differences in human platelet monoamine oxidase B (MAO B) activity do not reflect MAO B or MAO A levels in the brain. Cerebral cortical MAO A and MAO B activities, however, were correlated.
Area of Science:
- Neuroscience
- Biochemistry
- Enzymology
Background:
- Monoamine oxidase (MAO) enzymes, MAO A and MAO B, are crucial in neurotransmitter metabolism.
- While both MAO isoforms are found in the human brain, only MAO B is present in platelets.
Purpose of the Study:
- To investigate if platelet MAO B activity variations correlate with cerebral cortical MAO A and MAO B activities.
- To determine the relationship between MAO A and MAO B activities within the human cerebral cortex.
Main Methods:
- Assessed MAO A and MAO B activities in platelets and cerebral cortex samples from 14 epilepsy patients undergoing neurosurgery.
- Optimized assay conditions for accurate measurement of enzyme activities in both tissue types.
Main Results:
- No significant correlation was found between platelet MAO B activity and cerebral cortical MAO B activity.
- Platelet MAO B activity did not correlate with cerebral cortical MAO A activity.
- A significant positive correlation was observed between cerebral cortical MAO A and MAO B activities.
Conclusions:
- Platelet MAO B activity is not a reliable indicator of MAO B or MAO A levels in the human cerebral cortex.
- Cerebral cortical MAO A and MAO B activities exhibit inter-individual variability and are positively correlated.