title: Conditioning of beta(1)-adrenoceptor effect via beta(2)-subtype on L-type Ca(2+) current in canine ventricular myocytes.
abstract: We investigated the roles of beta(1)- and beta(2)-receptors (beta-AR) in adrenergic enhancement of L-type Ca(2+) current (I(CaL)) in canine ventricular myocytes. Isoproterenol and l-norepinephrine produced a monophasic and a biphasic concentration-I(CaL) relationship (CR), respectively. alpha(1)-AR inhibition with prazosin and beta(2)-AR stimulation with zinterol or l-epinephrine shifted the CR of l-norepinephrine leftward. Zinterol (50 nM) and l-epinephrine (10 nM), but not prazosin, altered the biphasic CR of l-norepinephrine to a monophasic CR. Zinterol and l-epinephrine applied after l-norepinephrine had no effect on I(CaL). beta(2)-AR inhibition with ICI-118551 reduced the E(max) of isoproterenol and l-norepinephrine by 60% and abolished the augmentation of l-norepinephrine by zinterol and l-epinephrine. Carbachol (100 nM) modestly reduced the I(CaL) response to beta(1)-AR stimulation but abolished the enhancement via beta(2)-AR. Zinterol augmented the enhancement of I(CaL) by forskolin, IBMX, and theophylline, but not in the presence of CGP-20712A. We conclude that selective beta(2)-AR stimulation does not increase I(CaL) but enhances adenylyl cyclase activity when stimulated via beta(1)-AR and with forskolin. beta(2)-AR activity preconditions adenylyl cyclase for beta(1)-AR stimulation.
authors.affiliation: Section of Endocrinology, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Nagykaldi
authors.forename: D
authors.initials: D
authors.lastname: Kem
authors.forename: R
authors.initials: R
authors.lastname: Lazzara
authors.forename: B
authors.initials: B
authors.lastname: Szabo
mesh_terms: D000322:Adrenergic Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D018679:Cholinergic Agonists / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*
chemical_list: D000322:Adrenergic Agonists; D000317:Adrenergic alpha-Antagonists; D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000319:Adrenergic beta-Antagonists; D020746:Calcium Channels, L-Type; D018679:Cholinergic Agonists; D010726:Phosphodiesterase Inhibitors; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D005576:Colforsin; D009638:Norepinephrine; D004837:Epinephrine