The effect of magnesium and calcium ions on adenosine triphosphatase in the nervous and vascular tissues of the brain

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Abstract
Two tissue fractions were separated from rat brain, one fraction consisting mainly of tissue of mesodermal origin and the other mainly of tissue of ectodermal origin. Adenosine triphosphatase (ATP) activity was studied quantitatively in saline suspensions prepared from these fractions and qualitatively by histological staining of enzymically active sites in frozen-dried sections from rat brain. The ATP activity of both fractions is of a similar order in the absence of added bivalent cations. The activity of the "meso-dermal" fraction is increased more than 15-fold by the presence of 10 m[image] calcium ions, and to a lesser extent by 3 m[image] Mg ions. The ATP of the "ectodermal" fraction is more sensitive to Mg ions, an activation of about 200% being obtained at 8 m[image] con-centration, than to Ca ions, which activate only about 60% at 3 m[image] concentration. The staining of brain vessels was accelerated much more by Ca ions than by Mg ions. The staining of neuronal and glial nuclei was accelerated by Mg ions but not by Ca ions. A lead-salt concentration of 4 m[image] preferentially inhibited the staining of nervous-tissue elements. The significance of these results is discussed in relation to the preparation, properties and function of brain ATP.