540 mg/day

Rubidium chloride accelerated cAMP synthesis in rat brain cortex membranes. The effect was dose-dependent and yielded above 2-fold activation of adenylate cyclase. It has been shown that Rb+ influenced directly the catalytic subunit of the enzyme and did not substitute Mg2+ in formation of the metal-ATP complex in this reaction. The stimulatory effect of Rb+ was additive to the activation of adenylate cyclase by the half-maximal (0.3 microM) as well as by the saturating (10 microM) forskolin concentrations, pointing to the fact that these effectors activate different isoforms of the enzyme in rat brain cortex.