title: Two distinct inhibitory actions of steroids on cholinoceptor-mediated secretion of catecholamine from guinea-pig adrenal medullary cells.
abstract: We investigated the effects of dexamethasone, cortisol and aldosterone on responses to nicotine and muscarine in guinea-pig isolated adrenal medullary cells. Nicotine-induced inward currents were reversibly inhibited by these steroids in a dose-dependent and non-competitive manner. These steroids inhibited an increase in [Ca2+](i) in response to nicotine but not muscarine. Muscarine-induced catecholamine secretion was inhibited by cortisol and aldosterone but not dexamethasone. Phorbol 12-myristate 13-acetate, a protein kinase C activator, caused catecholamine secretion which was inhibited by cortisol and aldosterone but not dexamethasone. These results suggest that catecholamine secretion induced by cholinoceptor stimulation is inhibited by steroids via two distinct mechanisms; one is the inhibition of nicotinic receptors, another is the inhibition of protein kinase C activation in guinea-pig adrenal medullary cells.
authors.affiliation: Laboratory of Pharmacology, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Yonekubo
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohta
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ito
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D018680:Cholinergic Antagonists / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology*; D006168:Guinea Pigs; D006854:Hydrocortisone / Q000494:pharmacology*; D007700:Kinetics; D009116:Muscarine / Q000494:pharmacology*; D009538:Nicotine / Q000494:pharmacology*; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000502:physiology*; D013256:Steroids / Q000494:pharmacology*
chemical_list: D002395:Catecholamines; D018680:Cholinergic Antagonists; D011950:Receptors, Cholinergic; D013256:Steroids; D000450:Aldosterone; D009538:Nicotine; D003907:Dexamethasone; D009116:Muscarine; D006854:Hydrocortisone