Reversibility of the ionomycin promoted synaptosomal hydrogen peroxide production

We previously reported on the release of hydrogen peroxide from guinea pig cerebral cortex synaptosomes (13). An important finding was that in glutathione depleted synaptosomes a linear release of hydrogen peroxide is rapidly induced on addition of the Ca ++-ionophore ionomycin (in the presence of Ca ++) or upon depolarization of the plasma membrane. We report here that the ionomycin induced hydrogen peroxide is reversed following the addition of bovine serum albumin which strongly binds the ionophore, to be reactivated by further addition of excess ionomycin, or of the depolarizing agent KCl. Similarly, the effect of ionomycin, or removed on decreasing the concentration of free Ca ++. Bovine serum albumin, which counteracts the effect of ionomycin on the release of H 2O 2, also counteracts the effect of the ionophore on the movements of Ca ++ and the release of γ-aminobutyrate. These findings support the idea that the synaptosomal production of H 2O 2 is a carefully controlled important physiological event.