Mechanisms of beta 3-adrenoceptor-induced eNOS activation in right atrial and left ventricular human myocardium.
beta-Adrenoceptors are important modulators of cardiac function. The present study investigated beta(3)-adrenergic eNOS activation in human myocardium. We measured nitric oxide (NO) liberation (diaminofluorescence) and signal transduction (immunohistochemistry, phosphorylation of eNOS(Ser1177), eNOS(Thr495), eNOS(Ser114), Akt/protein kinase B (Akt/PKB), and eNOS translocation) in human right atrial (RA, aortocoronary-bypass OP) and left ventricular nonfailing (LV, rejected donor hearts) myocardium after application of BRL 37344 (BRL), a preferential beta(3)-adrenoceptor agonist. In both RA and LV, BRL (10 microl) induced a liberation of NO. An eNOS activation via translocation was only observed in RA after application of BRL (10 microM). Yet, the NO liberation in both LV and RA was accompanied by phosphorylation of eNOS(Ser1177) and Akt/PKB. BRL-induced eNOS phosphorylation was abolished by LY292004, a blocker of PI-3 kinase. eNOS-Ser(114) phosphorylation was unchanged in RA, but decreased in LV after beta(3)-adrenergic stimulation. BRL did not alter phosphorylation of eNOS(Thr495). In conclusion, receptor-dependent eNOS activation is differentially regulated in the human heart. In the left ventricle, eNOS activation via phosphorylation seems to be of major importance, whereas in human atrial myocardium eNOS translocation is the predominant mechanism induced by beta(3)-adrenergic activation.
Laboratory of Muscle Research and Molecular Cardiology, Dept. of Internal Medicine III, University of Cologne, Joseph-Stelzmann-Str. 9, 50924 Cologne, Germany.
Klara
K
Brixius
Wilhelm
W
Bloch
Christian
C
Pott
Andreas
A
Napp
Andreas
A
Krahwinkel
Christoph
C
Ziskoven
Marco
M
Koriller
Uwe
U
Mehlhorn
J
J
Hescheler
Bernd
B
Fleischmann
Robert H G
RH
Schwinger
D058667:Adrenergic beta-3 Receptor Agonists; D000328:Adult; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D006325:Heart Atria / Q000187:drug effects / Q000201:enzymology; D006352:Heart Ventricles / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism*
D058667:Adrenergic beta-3 Receptor Agonists; D004983:Ethanolamines; D022702:Receptors, Adrenergic, beta-3; C057368:BRL 37344; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III