Increase of brain ammonia after microwave irradiation and its mechanism.

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.