title: Reduced density and altered regulation of rat atrial L-type Ca2+current in heart failure.
abstract: Constitutive regulation by PKA has recently been shown to contribute to L-type Ca2+current (ICaL) at the ventricular t-tubule in heart failure. Conversely, reduction in constitutive regulation by PKA has been proposed to underlie the downregulation of atrialICaLin heart failure. The hypothesis that downregulation of atrialICaLin heart failure involves reduced channel phosphorylation was examined. Anesthetized adult male Wistar rats underwent surgical coronary artery ligation (CAL,N=10) or equivalent sham-operation (Sham,N=12). Left atrial myocytes were isolated ~18 wk postsurgery and whole cell currents recorded (holding potential=-80 mV).ICaLactivated by depolarizing pulses to voltages from -40 to +50 mV were normalized to cell capacitance and current density-voltage relations plotted. CAL cell capacitances were ~1.67-fold greater than Sham (P≤ 0.0001). MaximalICaLconductance (Gmax) was downregulated more than 2-fold in CAL vs. Sham myocytes (P< 0.0001). Norepinephrine (1 μmol/l) increasedGmax>50% more effectively in CAL than in Sham so that differences inICaLdensity were abolished. Differences between CAL and ShamGmaxwere not abolished by calyculin A (100 nmol/l), suggesting that increased protein dephosphorylation did not account forICaLdownregulation. Treatment with either H-89 (10 μmol/l) or AIP (5 μmol/l) had no effect on basal currents in Sham or CAL myocytes, indicating that, in contrast to ventricular myocytes, neither PKA nor CaMKII regulated basalICaLExpression of the L-type α1C-subunit, protein phosphatases 1 and 2A, and inhibitor-1 proteins was unchanged. In conclusion, reduction in PKA-dependent regulation did not contribute to downregulation of atrialICaLin heart failure.NEW & NOTEWORTHYWhole cell recording of L-type Ca2+currents in atrial myocytes from rat hearts subjected to coronary artery ligation compared with those from sham-operated controls reveals marked reduction in current density in heart failure without change in channel subunit expression and associated with altered phosphorylation independent of protein kinase A.
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Bond
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Bryant
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
authors.forename: Judy J
authors.initials: JJ
authors.lastname: Watson
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
authors.forename: Jules C
authors.initials: JC
authors.lastname: Hancox
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom.
authors.forename: Clive H
authors.initials: CH
authors.lastname: Orchard
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom a.james@bristol.ac.uk.
authors.forename: Andrew F
authors.identifier: http://orcid.org/0000-0002-2035-9489
authors.initials: AF
authors.lastname: James
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006325:Heart Atria / Q000378:metabolism* / Q000503:physiopathology; D006333:Heart Failure / Q000378:metabolism* / Q000503:physiopathology; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D009638:Norepinephrine / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D017868:Cyclic AMP-Dependent Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D010744:Phosphoric Monoester Hydrolases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D009638:Norepinephrine
keywords: atrial remodeling; coronary artery ligation; voltage-gated Ca2+ channel