ACTIVATION OF CAMP SYNTHESIS IN RAT-BRAIN CORTICAL MEMBRANES BY RUBIDIUM AND CESIUM IONS

Rubidium and cesium chlorides accelerated cAMP synthesis in rat brain cortex membranes, while other alkali metal chlorides had no influence on the rate of this process. The effect was dose-dependent and yielded above 2-fold activation of adenylate cyclase. It has been shown that Rb+ and Cs+ influenced directly the catalytic subunit of the enzyme an d did not substitute Mg2+ in formation of the metal-ATP complex in thi s reaction. The stimulatory effect of Rb+ was additive to the activati on of adenylate cyclase by the half-maximal (0.3 mu M) as well as by t he saturating (10 mu M) forskolin concentrations, pointing to the fact that these effecters activate different isoforms of the enzyme in rat brain cortex.