Functional Selectivity of Muscarinic Receptor Antagonists for Inhibition of M3-Mediated Phosphoinositide Responses in Guinea Pig Urinary Bladder and Submandibular Salivary Gland
Binding and functional affinities of the muscarinic acetylcholine (mACh) receptor antagonists darifenacin, tolterodine, oxybutynin, and atropine were assessed in Chinese hamster ovary (CHO) cells expressing the human recombinant M 2 (CHO-m2) or M 3 (CHO-m3) receptors, and in guinea pig bladder and s...
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Published in | The Journal of pharmacology and experimental therapeutics Vol. 310; no. 3; pp. 1255 - 1265 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Pharmacology and Experimental Therapeutics
01.09.2004
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Subjects | |
Online Access | Get full text |
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Summary: | Binding and functional affinities of the muscarinic acetylcholine (mACh) receptor antagonists darifenacin, tolterodine, oxybutynin,
and atropine were assessed in Chinese hamster ovary (CHO) cells expressing the human recombinant M 2 (CHO-m2) or M 3 (CHO-m3) receptors, and in guinea pig bladder and submandibular gland. In [ N -methyl- 3 H]scopolamine methyl chloride binding studies in CHO cells, darifenacin displayed selectivity (14.8-fold) for the M 3 versus M 2 mACh receptor subtype. Oxybutynin was nonselective, whereas atropine and tolterodine were weakly M 2 -selective (5.1- and 6.6-fold, respectively). Antagonist functional affinity estimates were determined by the inhibition of
agonist-induced [ 3 H]inositol phosphate accumulation in CHO-m3 cells and antagonism of the agonist-induced inhibition of forskolin-stimulated
cyclic AMP accumulation in CHO-m2 cells. Darifenacin was the most M 3 -selective antagonist (32.4-fold), whereas oxybutynin, atropine, and tolterodine exhibited lesser selectivity. Functional
affinity estimates in guinea pig urinary bladder and submandibular salivary gland using indices of phosphoinositide turnover
revealed that oxybutynin, darifenacin, and tolterodine each displayed selectivity for the response in the bladder, relative
to that seen in the submandibular gland (9.3-, 7.9-, and 7.4-fold, respectively). In contrast, atropine displayed a similar
affinity in both tissues. These data demonstrate that in bladder, compared with submandibular gland from a single species,
the mACh receptor antagonists darifenacin, tolterodine, and oxybutynin display selectivity to inhibit agonist-mediated phosphoinositide
responses. It is proposed that both responses are mediated via M 3 mACh receptor activation and that differential functional affinities displayed by some, but not all, antagonists are indicative
of the influence of cell background upon the pharmacology of the M 3 mACh receptor. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3565 1521-0103 |
DOI: | 10.1124/jpet.104.067140 |