Influence of thiol groups, calcium, and glucose metabolism on cholinergic-induced insulin release and on methylscopolamine binding to muscarinic receptors in pancreatic islets of the rat
Grill, V.; Fåk, K.
Acta Endocrinologica 109(3): 355-360
1985
ISSN/ISBN: 0001-5598 PMID: 2411095 Document Number: 242450
Short-term regulation of [3H]methylscopolamine binding to muscarinic receptors and acetylcholine-induced stimulation of insulin release was investigated in pancreatic islets of the rat. Binding of methylscopolamine was reversible; 47% of level was displaced 10 min and 70% 30 min after addition of unlabeled substance; 0.1 mM chlormercuribenzoic acid, when present during binding incubations, inhibited binding by 54%; acetylcholine-induced insulin release was unaffected by the presence of the thiol reactant. Preincubation for 60 min in a Ca-deprived medium or in the presence of 50 .mu.M trifluoroperazine likewise inhibited binding. Pre-incubation with 1.0 mM 3-isobutyl-1-methylxanthine or 16.7 M glucose failed to influence subsequent binding although acetylcholine-induced insulin release was 4-fold enhanced by priming with glucose. Binding to muscarinic receptors is influenced by thiol interaction. Short-term alterations in Ca fluxes influence binding; short-term changes in cAMP or glucose metabolism do not. A priming effect of glucose on insulin secretion is not mediated by changes in receptor binding.