Interaction of vanadate with isolated rat parotid acini.

1. In rat parotid acini, vanadate affects amylase secretion and intracellular messengers according to its concentration. 2. Low concentrations (in the micromolar range) concentrations of vanadate stimulate amylase secretion and potentiate the secretory effect of carbamylcholine, but inhibit the amylase release in response to isoproterenol. 3. Vanadate increases inositol phosphates (mono-, bis- and trisphosphate) and potentiate the stimulatory effect of carbachol on inositol bis- and trisphosphate. 4. Vanadate also decreases the intracellular cyclic AMP concentration and the increase in response to isoproterenol or forskolin. 5. High concentrations (in the millimolar range) of vanadate inhibit the increase in inositol phosphate induced by carbachol. 6. It is concluded that low concentrations of vanadate activate regulatory proteins coupled to phospholipase C and adenylate cyclase while high concentrations of vanadate inhibit inositol bisphosphatase.