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Cardiovascular Research 2003 57(3):694-703; doi:10.1016/S0008-6363(02)00720-4
© 2003 by European Society of Cardiology
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Copyright © 2003, European Society of Cardiology

New insights into β2-adrenoceptor signaling in the adult rat heart

Sabine Bartel*, Ernst-Georg Krause, Gerd Wallukat and Peter Karczewski

Max Delbrück Center for Molecular Medicine, Robert Rössle Strasse 10, D-13125 Berlin, Germany

s.bartel{at}mdc-berlin.de

* Corresponding author. Tel.: +49-30-9406-2519; fax: +49-30-9406-2110.

Objective: The role of cAMP in β2-adrenoceptor signaling and its functional relevance in adult rat heart has been the subject of considerable controversy. Therefore, we investigated the β2-adrenoceptor pathways in both adult cardiomyocytes and in the intact hearts of Wistar rats with respect to protein kinase A (at Ser16)-, the key event in shortening of relaxation time, and CaM kinase II (at Thr17)-dependent phospholamban phosphorylation. Methods: Contractile and cellular β1/β2-adrenergic responses were studied in parallel on the same perfused rat heart. (–)Isoproterenol and the β2-adrenergic agonists zinterol and procaterol were used to discriminate the β-adrenoceptor subtype-related actions. Results: β2-Adrenoceptor stimulation induces protein kinase A-dependent phospholamban phosphorylation in both adult cardiomyocytes and in adult hearts of rats. The β2-adrenoceptor-mediated shortening of relaxation time in the heart correlates with Ser16 phosphorylation. Adenosine elicited antiadrenergic action on both β1- and β2-adrenergic signaling cascades by reducing the phosphorylation status of phospholamban. Only β1-adrenoceptor stimulation produced significant CaM kinase II-related Thr17 phosphorylation, troponin I phosphorylation and activation of phosphorylase a. Conclusions: Our findings clearly show that β2-adrenoceptor signaling is coupled to phospholamban phosphorylation and shortening of relaxation time in the adult rat heart.

KEYWORDS Adrenergic (ant)agonists; Myocytes; Receptors; Signal transduction


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