[Calcium and ammonia stimulate monoamine oxidase A activity in brain mitochondria].

The effect of ammonia and calcium on the activity of monoamine oxidase (MAO) was studied. The enzyme activity in non-synaptic brain mitochondria isolated from rats administered with ammonium acetate was assayed by release of H2O2 using spectrophotometry. The effect of calcium on MAO was assayed directly after addition of Ca2+ to the non-synaptic mitochondria isolated from the forebrain of the control rats. Both ammonium acetate injection in vivo and Ca2+ addition in vitro stimulated the activity of MAO A but not that of MAO B in mitochondria. This is the first evidence that ammonia and Ca2+ regulate MAO A in non-synaptic mitochondria in the forebrain and can contribute to oxidative stress in the neurons via MAO A activation.