Mixed nicotinic and muscarinic features of cholinergic receptor coupled to secretion in bovine chromaffin cells

M. H. Shirvan, H. B. Pollard, E. Heldman

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24 Scopus citations

Abstract

Acetylcholine evokes release from cultured bovine chromaffin cells by a mechanism that is believed to be classically nicotinic. However, we found that the full muscarinic agonist oxotremorine-M (Oxo-M) induced a robust catecholamine (CA) secretion. By contrast, muscarine, pilocarpine, bethanechol, and McN-A-343 did not elicit any secretory response. Desensitization of the response to nicotine by Oxo-M and desensitization of the response to Oxo-M by nicotine suggest that both nicotine and Oxo-M were acting at the same receptor. Additional experiments supporting this conclusion show that nicotine-induced secretion and Oxo-M-induced secretion were similarly blocked by various muscarinic and nicotinic antagonists. Moreover, secretion induced by nicotine and Oxo-M were Ca2+ dependent, and both agonists induced 45Ca2+ uptake. Equilibrium binding studies showed that [3H]Oxo-M bound to chromaffin cell membranes with a K(d) value of 3.08 x 10-8 M and a Hill coefficient of 1.00, suggesting one binding site for this ligand. Nicotine inhibited Oxo-M binding in a noncompetitive manner, suggesting that both ligands bind at two different sites on the same receptor. We propose that the receptor on bovine chromaffin cells that is coupled to secretion represents an unusual cholinergic receptor that has both nicotinic and muscarinic features.

Original languageEnglish
Pages (from-to)4860-4864
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume88
Issue number11
DOIs
StatePublished - 1 Jan 1991
Externally publishedYes

ASJC Scopus subject areas

  • General

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