1987 Fiscal Year Final Research Report Summary
Subtypes of muscarinic acetylcholine receptor and their receptor responses
| Project/Area Number |
61570102
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General pharmacology
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| Research Institution | Osaka University |
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Principal Investigator |
UCHIDA Shuji Associate Prof. Osaka Univ., 医学部, 助教授 (90028639)
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| Co-Investigator(Kenkyū-buntansha) |
OSUGI Takeshi Assistant Osaka Univ., 医学部, 助手 (50176880)
WATANABE Yasuhiro Assistant Prof. Osaka Univ., 医学部, 講師 (90127324)
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| Project Period (FY) |
1986 – 1987
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| Keywords | muscarinic acetylcholine receptor / adenylate cyclase |
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| Research Abstract |
M2 subtype of mubtype of muscarinic acetylcholine receptors (m-AChR) consists of beterogeneous states and/or subclasses which have different affinities for an agonist but single affinity for an antagonist. We characterized the heterogeniety of agonist bindings and their relationship to receptor-mediated responses in guinea pig hearts.
M2 m-AChR had three types of binding sites with different affinities for carbachol and ACh (super-high (SH), high (H) and low (L) sites). Distribution of those sites were changed by guanine nucleotide and sulfhydryl reagent. Similar results were obtained when oxtremorine and pilocarpine were used as agonists, though affinities of H and L sites for these agonists were too similar to allow their differentiation.
Alkylation of m-AChR by propylbenzilylcholine mustard (PrBCM) under the protection of SH site by carbachol eliminated L site only. Residual SH and H sites were interconvertible by the treatment of fuanine nucleotide and sulfhydryl reagent. These results suggest that M2 could be divided into two classes, one is SH-H interconvertible class and the other is H-L interconvertible class.
ED_<50> of negative inotropic action and inhibition of adenylate cyclase corresponded with the affinity of H site after alkylation of spare receptor by PrBCM. M-AChR-mediated inhibition of adenylate cyclase remained after alkylation of H-L class by PrBCM-treatment under the protection of SH-H class with carbachol. On the other hand, ED_<50> of m-AChR-mediated activation of PI turnover measured by IP_3 formation corresponded with the affinity of L site.
These results indicate that H state of SH-H class is responsible for the inhibition of adenylate cyclase and L state of H-L class for PI turnover.
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