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Effect of ether, chloroform and carbon dioxide on monoamine inactivation
Abstract:
To determine if anaesthetic agents alter monoamine inactivation, we exposed tissue homogenates (liver, kidney and brain) from mice and rabbits to ether and chloroform vapors and carbon dioxide gas. These anaesthetic agents inhibited monoamine oxidase (MAO) activity against typtamine and serotonin. Concentrations of anaesthetic agents that are achieved in the plasma of man during general anaesthesia caused a 27% (ether) and 49% (chloroform) reduction in mouse liver MAO; higher concentrations caused a 95% inhibition mouse or rabbit liver MAO. Kinetic analysis with tryptamine as substrate indicate that ether and chloroform are noncompetitive, reversible MAO inhibitors that preferentially inhibit Type B MAO. Ether and chloroform cause noncompetitive inhibition of serotonin oxidation by mouse liver MAO and competitive inhibition of serotonin oxidation by mouse brain and kidney MAO. Ether or chloroform did not alter catechol-O-methyltransferase activity from tissues of mice. Isolated blood platelets (rabbit and human) were used as a model system for neuronal uptake. Ether caused an irreversible inhibition of serotonin uptake by platelets.
Insights
Anesthetics like ether and chloroform inhibit monoamine oxidase (MAO), an enzyme crucial for neurotransmitter breakdown. This study reveals their impact on MAO activity and serotonin uptake, with implications for anesthetic drug development.
Area of Science:
- Biochemistry
- Pharmacology
- Neuroscience
Background:
- Monoamine oxidase (MAO) is vital for inactivating neurotransmitters like serotonin.
- Understanding how anesthetics affect neurotransmitter metabolism is crucial for patient safety.
Purpose of the Study:
- To investigate the effects of common anesthetic agents on monoamine inactivation pathways.
- To determine if ether, chloroform, and carbon dioxide impact MAO and catechol-O-methyltransferase (COMT) activities.
Main Methods:
- Tissue homogenates (liver, kidney, brain) from mice and rabbits were exposed to anesthetic vapors.
- Enzyme kinetics and substrate inhibition assays were performed.
- Serotonin uptake in isolated platelets was assessed.
Main Results:
- Ether and chloroform significantly inhibited MAO activity in a dose-dependent manner.
- These agents acted as noncompetitive, reversible inhibitors, preferentially targeting MAO Type B.
- Ether also irreversibly inhibited serotonin uptake in platelets.
Conclusions:
- Anesthetic agents can disrupt monoamine metabolism by inhibiting MAO.
- Ether and chloroform exhibit distinct inhibitory mechanisms.
- Further research is needed to understand the clinical significance of these findings.