Chelating Agents, Barbiturates, and Stimulation of Rat Brain Adenosinetriphosphatase

Abstract

The order of activity of barbiturates in stimulating the adenosinetriphosphatase activity (ATPase) of rat liver homogenates was thiopental >thiamylal >pentobarbital> phenobarbital >barbital. The ATPase of brain homogenates was not affected under the same conditions by the barbiturates, 2,4-dinitrophenol, chlortetracycline, or chloramphenicol. When ethylenediamine-tetra acetic acid (EDTA) was added either before or after homogenization, so that the final concentration of EDTA in the assay system was 10-4 [image], the ATPase of brain homogenates was considerably reduced and susceptible to stimulation by the above agents. The order of activity of the barbiturates in stimulating brain ATPase was pentobarbital > amytal > thiamylal >phenobarbital > barbital. Besides EDTA, ammoniatriacetic acid and 1,2-diaminocyclohexane-N,N'' -tetra acetic acid were effective in reducing brain ATPase and allowing subsequent stimulation.