Abstract
In dispersed acini from guinea pig pancreas, replacing extracellular sodium by tetraethylammonium (1) abolished carbamylcholine-stimulated amylase secretion but did not alter the increase in amylase secretion caused by the C-terminal octapeptide of cholecystokinin, bombesin, ionophore A23187, vasoactive intestinal peptide or 8-bromoadenosine 3′:5′ monophosphate, (2) caused a parallel rightward shift in the dose-response curve for carbamylcholine-stimulated amylase secretion and (3) inhibited binding of N-[3H]methyl scopolamine to muscarinic cholinergic receptors. Detectable inhibition of carbamylcholine-stimulated amylase secretion and binding of N-[3H]methyl scopolamine occurred with 300 μM tetraethylammonium, and half-maximal inhibition of these functions occurred with 1–2 mM tetraethylammonium. Replacing extracellular sodium by Tris did not alter the stimulation of enzyme secretion caused by any secretagogue tested. These results indicate that the tetraethylammonium is a muscarinic cholinergic receptor antagonist and that enzyme secretion from pancreatic acini does not depend on extracellular sodium.
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