The release of 3H-1-methyl-4-phenylpyridinium from bovine adrenal chromaffin cells is modulated by somatostatin.
Besides cholinergic regulation, catecholamine secretion from adrenal chromaffin cells can be elicited and/or modulated by noncholinergic neurotransmitters and hormones. This study was undertaken to investigate the influence of somatostatin and octreotide on [3H]MPP+ secretion evoked by KCl or cholinergic agents, from bovine adrenal chromaffin cells. The release of [3H]MPP+ was markedly increased by excess KCl (50 mM), acetylcholine (50 microM-10 mM) and by the nicotinic agonists, nicotine (5-100 microM) and 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP, 10-100 microM), but not by the muscarinic agonist, pilocarpine (10-100 microM). Acetylcholine-evoked release of [3H]MPP+ from these cells was mainly mediated by nicotinic receptors: a) nicotine and DMPP stimulated the release of [3H]MPP+, b) a nicotinic antagonist, hexamethonium, markedly blocked the acetylcholine-evoked response and c) pilocarpine was devoid of effect on [3H]MPP+ secretion. At all concentrations tested, somatostatin and octreotide interfered neither with [3H]MPP+ basal release nor with KCl-induced release of [3H]MPP+. However, somatostatin (0.01-0.3 microM) increased the release of [3H]MPP+ induced by a high concentration of acetylcholine (10 mM). Octreotide (1-10 microM) had no effect. These results, showing that somatostatin potentiates acetylcholine-induced [3H]MPP+ release, support the hypothesis that somatostatin may increase the release of catecholamines from adrenal medullary cells.
Ribeiro
Laura
L
Department of Biochemistry (U38-FCT), Faculty of Medicine, 4200-319 Porto, Portugal. lribeiro@med.up.pt
Martel
Fátima
F
Azevedo
Isabel
I
D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism*; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism*; D066298:In Vitro Techniques; D015282:Octreotide / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism; D013004:Somatostatin / Q000494:pharmacology*
D002395:Catecholamines; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D011978:Receptors, Nicotinic; D013004:Somatostatin; D011189:Potassium Chloride; D000109:Acetylcholine; D015655:1-Methyl-4-phenylpyridinium; D015282:Octreotide