caa a22 4500 477120806 CHVBK 20180405111636.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00408647 doi (NATIONALLICENCE)springer-10.1007/BF00408647 β2-Adrenoceptor activation by zinterol causes protein phosphorylation, contractile effects and relaxant effects through a cAMP pathway in human atrium [Elektronische Daten] [Alberto Kaumann, Louise Sanders, James Lynham, Sabine Bartel, Meike Kuschel, Peter Karczewski, Ernst-Georg Krause] Evidence from ventricular preparations of cat, sheep, rat and dog suggests that both β1-adrenoceptors (β1AR) and β2-adrenoceptors (β2AR) mediate positive inotropic effects but that only β1AR do it through activation of a cAMP pathway. On the other hand, our evidence has shown that both β1 AR and β2 AR hasten relaxation of isolated human myocardium consistent with a common cAMP pathway. We have now investigated in the isolated human right atrial appendage, a tissue whose β-AR comprise around 2/3 of β1AR and 1/3 of β2AR, whether or not β2AR-mediated effects occur via activation of a cAMP pathway. We carried out experiments on atria obtained from patients without advanced heart failure undergoing open heart surgery. To activate β2AR, we used the β2AR-selective ligand zinterol. Experiments were carried out on paced atrial strips (1 Hz) and tissue homogenates and membrane particles. Zinterol caused positive inotropic and lusitropic (i.e. reduction of t1:2 of relaxation) effects with EC50 values of 3 and 2 nM, respectively. The zinterol-evoked effects were unaffected by the β AR-selective antagonist CGP 20712A (300 nM) but blocked surmountably by the β2AR-selective antagonist ICI 118551 (50 nM) which reduced both EC50 values to 1 μM. Zinterol stimulated adenylyl cyclase activity with an EC50 of 30 nM and intrinsic activity of 0.75 with respect to (−)-isoprenaline (600 μM); the effects were resistant to blockade by CGP 20712A (300 nM) but antagonised surmountably by ICI 118551 (50 nM). Zinterol bound to membrane PAR labelled with (−)-[125I] cyanopindolol with higher affinity for β2AR than for β- 1 AR; the binding to β2AR but not to β- BAR was reduced by GTPyS (10 μM). In the presence of CGP 20712A (300 nM) (−)-isoprenaline (400 μM); (to activate both β1AR and β2AR maximally) and zinterol (10 μM); increased contractile force 3.4-fold and 2.5-fold respectively and reduced relaxation tut by 32% and 18% respectively. These effects of (−)-isoprenaline and zinterol were associated (5 min incubation) with phosphorylation (pmol P/mg supernatant protein) of troponin I and C-protein to values of 8.4 ± 2.0 vs 12.4 ± 2.3 and 10.1 ± 2.5 vs 8.6 ± 1.6 respectively. (−)-Isoprenaline and zinterol also caused phosphorylation of phospholamban (1.8 ± 0.3 vs 0.4 ± 0.1 pmol P/mg respectively) specifically at serine residues. We conclude that in human atrial myocardium activation of both β1AR and β2AR leads to cAMP-dependent phosphorylation of proteins involved in augmenting both contractility and relaxation. Kluwer Academic Publishers, 1996 human atrium nationallicence β2-adrenoceptors nationallicence receptor binding nationallicence zinterol nationallicence adenylyl cyclase stimulation nationallicence atrial relaxation and contraction nationallicence protein phosphorylation nationallicence troponin I nationallicence C-protein nationallicence phospholamban nationallicence Kaumann Alberto Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut Sanders Louise Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut Lynham James Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut Bartel Sabine Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut Kuschel Meike Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut Karczewski Peter Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut Krause Ernst-Georg Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 163-164/1(1996-03-01), 113-123 0300-8177 163-164:1<113 1996 163-164 11010 https://doi.org/10.1007/BF00408647 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00408647 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kaumann Alberto Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut NATIONALLICENCE 700 1- Sanders Louise Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut NATIONALLICENCE 700 1- Lynham James Human Pharmacology Laboratory, The Babraham Institute, CB2 4AT, Cambridge, UK aut NATIONALLICENCE 700 1- Bartel Sabine Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut NATIONALLICENCE 700 1- Kuschel Meike Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut NATIONALLICENCE 700 1- Karczewski Peter Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut NATIONALLICENCE 700 1- Krause Ernst-Georg Max-Delbrück-Centrum für Molekulare Medizin, Forschungsschwerpunkt Kardiologie, Robert-Rössle-Straßie 10, 13122, Berlin, Germany aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www.wkap.nl 163-164/1(1996-03-01), 113-123 0300-8177 163-164:1<113 1996 163-164 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer