Tungstate Stimulates Adenylate Cyclase*

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Abstract
Tungstate stimulates adenylate cyclase (E.C.4.6.1.1) in ovarian homogenates of the rat; maximal stimulation (∼3-fold) is achieved at a concentration of 1 mM. This stimulation of cAMP production cannot be explained by the inhibition of phosphodiesterase activity or of ATP hydrolysis. Activation of adenylate cyclase by tungstate is rapid and reversible. The effects of tungstate and hCG on cyclase activity are additive, but tungstate does not augment fluoride-stimulated activity. At higher concentrations (5 and 10 mM), tungstate inhibits basal as well as hCG- and fluoride-stimulated cyclase activity in an irreversible manner. After solubilization by Lubrol-PX, the cyclase enzyme is inhibited by tungstate at concentrations ranging from 0.1-10 mM. Tungstate also activates adenylate cyclase in the brain, heart, lungs, kidneys, and liver of the rat. This suggests that tungstate activation of adenylate cyclase is a general phenomenon and may be mediated by a similar mechanism in different tissues. Tungstate p ovides an additional tool by which the molecular basis of adenylate cyclase activation can be probed. (Endocrinology108: 435, 1981)