- 作者: Laura Ribeiro; Fatima Martel; Isabel Azevedo
- 作者服務機構: Department of Biochemistry (U38-FCT), Faculty of Medicine, University of Porto, 4200-319, Porto, Portugal
- 中文摘要: --
- 英文摘要: The aim of this work was to investigate the effect of a short-term exposure to somatostatin (SS), its receptors (SSTR) selective agonists as well as muscarinic; receptors agonists upon acetylcholine-induced release of 3H-MPP+ from bovine adrenal medullary cells. Acetylcholine (ACH, 100, 500 μΜ) was found to increase the release of 3H-MPP+ by these cells (to 175 and 171% of basal release, respectively). ACH-elicited 3H-MPP+ release was significantly reduced by hexamethonium (100 μΜ) and atropine (100 μΜ), selective nicotinic and muscarinic antagonists, respectively. Previous exposure to any of two muscarinic agonists, oxotremorine or pilocarpine, led to a significant reduction of 3H-MPP+ release in response to 100 μΜ ACH, to about a maximum of 51% and 78% of control, respectively. Somatostatin (SS, 0.010.1 μΜ), previously applied to the preparation, depressed ACH-elicited 3H-MPP+ release by 25-27%, but only when a 500 μΜ ACH concentration was used. The inhibition exerted by SS upon ACH-evoked 3H-MPP+ release appeared to be mediated by its SSTR: (1) SSTR2, 3 and 4 subtype agonists mimicked the effects seen with SS, and (2) the SSTR non-selective antagonist, cyclo-SS, counteracted the SS inhibitory effect. When SS was tested in the presence of any of the muscarinic agonists, oxotremorine or pilocarpine, its inhibitory effect on 500 μΜ ACH-induced 3H-MPP+ release was no longer detectable. These results, showing a somewhat similar effect of short-term exposure to SS and muscarinic agonists over ACH-induced release of 3H-MPP+ , as well as the loss of effect of SS by the presence of the muscarinic agonists, suggest that these compounds may share signalling pathways.
- 中文關鍵字: --
- 英文關鍵字: adrenal medulla, MPP+ release, muscarinic receptors, somatostatin receptors