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Increase of brain ammonia after microwave irradiation and its mechanism
K Kobayashi1, M Horiuchi, S Hagihara
1Department of Biochemistry, Faculty of Medicine, Kagoshima University, Japan.
Abstract:
Microwave irradiation at 4kW for 0.4 sec applied to the heads of mice produced an increase in brain ammonia. This increase resulted from stimulated breakdown of glutamine initiated by microwave irradiation and proceeded until freezing of the brain. Two glutamine-related enzymes, in the brain, phosphate-dependent glutaminase (assayed in the presence of 200mM phosphate) and glutamine synthetase, were inactivated by microwave irradiation in a similar fashion. On the other hand, glutaminase activity in the presence of 10mM phosphate increased. This is considered to be a probable cause of the increase in brain ammonia. The increased 10mM-phosphate glutaminase activity remained stable in the precipitate fraction even after 5% Triton X-100 treatment.
Insights
Microwave irradiation significantly increased brain ammonia in mice by affecting glutamine metabolism. Specific enzyme changes, particularly increased glutaminase activity, were identified as the likely cause.
Area of Science:
- Neuroscience
- Biochemistry
- Biophysics
Background:
- Microwave irradiation is increasingly used in biological research.
- Understanding its biochemical effects on the brain is crucial.
- Ammonia plays a key role in brain function and dysfunction.
Purpose of the Study:
- To investigate the impact of microwave irradiation on brain ammonia levels.
- To identify the specific enzymatic mechanisms underlying ammonia changes.
- To characterize the stability of affected enzymes post-irradiation.
Main Methods:
- Exposure of mouse heads to 4kW microwave irradiation for 0.4 seconds.
- Assay of brain ammonia levels.
- Enzymatic assays for phosphate-dependent glutaminase and glutamine synthetase activity.
- Fractionation and detergent treatment to assess enzyme stability.
Main Results:
- Microwave irradiation elevated brain ammonia levels in mice.
- Glutamine breakdown was stimulated, leading to increased ammonia.
- Phosphate-dependent glutaminase (200mM phosphate) and glutamine synthetase were inactivated.
- Glutaminase activity significantly increased at 10mM phosphate.
- This elevated 10mM-phosphate glutaminase activity was stable in precipitate fractions.
Conclusions:
- Microwave irradiation induces significant changes in brain ammonia metabolism.
- The observed increase in brain ammonia is likely due to enhanced glutaminase activity at low phosphate concentrations.
- Specific glutamine-metabolizing enzymes exhibit differential sensitivity to microwave irradiation.
- The stability of the activated glutaminase suggests potential for targeted biochemical effects.