Tungstate Stimulates Adenylate Cyclase*

Abstract

Tungstate stimulates adenylate cyclase (E.C. 4.6.1.1) in ovarian homogenates of the rat; maximal stimulation (approximately 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 provides an additional tool by which the molecular basis of adenylate cyclase activation can be probed. (Endocrinology 108: 435, 1981)

Early hCG‐induced desensitization of rat ovarian LH/hCG receptors is associated with altered physical state of membranes

“…Adenylylcyclase activity was assayed at 30°C for 25 min with 30~0 gg plasma membrane protein [14,17]. RIA and protein binding methods were used for the determination of progesterone and cAMP concentration [8,9].…”

Functional reconstitution of rat ovarian LH/hCG receptor into proteoliposomes

“…Adenylate cyclase was assayed at 30°C for 25 min [12]. The assay system contained 25 mM Tris-HCl (pH 7.4), 5 mM MgCI2, 1 mM EDTA, 0.3 mM 3-isohutylmethylxanthine, 1 mM ATP, 20 mM phosphocreatine, 100 U/ml creatine kinase and 30-40 /~g protein of proteoliposomes or membrane preparations in a final volume of 400/A.…”

Polyoxotungstates Reduce the β-Lactam Resistance of Methicillin-Resistant Staphylococcus aureus

“…Although some prokaryotes are known to require tungsten as a cofactor of several enzymes, it is not thought that tungsten is essential for eukaryotes [90]. Some investigators have reported that WO 4 2-and molybdate (MoO 4 2-) stimulated the adenylate cyclase activity in rat brains [91,92], but the physiological significance of this is unclear.…”