251. Upregulation of functional beta(3)-adrenergic receptor in the failing canine myocardium.
- Author
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Cheng HJ, Zhang ZS, Onishi K, Ukai T, Sane DC, and Cheng CP
- Subjects
- Adrenergic beta-1 Receptor Antagonists, Adrenergic beta-2 Receptor Antagonists, Adrenergic beta-Agonists pharmacology, Adrenergic beta-Antagonists pharmacology, Animals, Blotting, Western, Calcium metabolism, Cardiac Pacing, Artificial adverse effects, Cell Separation, Disease Models, Animal, Disease Progression, Dogs, Dose-Response Relationship, Drug, Enzyme Inhibitors pharmacology, Ethanolamines pharmacology, Heart Failure etiology, Heart Failure pathology, Myocardial Contraction drug effects, Myocardium pathology, RNA, Messenger metabolism, Receptors, Adrenergic, beta-3 drug effects, Reverse Transcriptase Polymerase Chain Reaction, Heart Failure physiopathology, Myocardium metabolism, Receptors, Adrenergic, beta-3 genetics, Receptors, Adrenergic, beta-3 metabolism, Up-Regulation
- Abstract
Altered expression and functional responses to cardiac beta(3)-adrenergic receptors (ARs) may contribute to progressive cardiac dysfunction in heart failure (CHF). We compared myocyte beta(3)-AR mRNA and protein levels and myocyte contractile, [Ca(2+)](i) transient, and Ca(2+) current (I(Ca,L)) responses to BRL-37344 (BRL, 10(-8) mol/L), a selective beta(3)-AR agonist, in 9 instrumented dogs before and after pacing-induced CHF. Myocytes were isolated from left ventricular myocardium biopsy tissues. Using reverse transcription-polymerase chain reaction, we detected beta(3)-AR mRNA from myocyte total RNA in each animal. Using a cloned canine beta(3)-AR cDNA probe and myocyte poly A(+) RNA, we detected a single band about 3.4 kb in normal and CHF myocytes. beta(3)-AR protein was detected by Western blot. beta(3)-AR mRNA and protein levels were significantly greater in CHF myocytes than in normal myocytes. Importantly, these changes were associated with enhanced beta(3)-AR-mediated negative modulation on myocyte contractile response and [Ca(2+)](i) regulation. Compared with normal myocytes, CHF myocytes had much greater decreases in the velocity of shortening and relengthening with BRL accompanied by larger reductions in the peak systolic [Ca(2+)](i) transient and I(Ca,L). These responses were not modified by pretreating myocytes with metoprolol (a beta(1)-AR antagonist) or nadolol (a beta(1)- and beta(2)-AR antagonist), but were nearly prevented by bupranolol or L-748,337 (beta(3)-AR antagonists). We conclude that in dogs with pacing-induced CHF, beta(3)-AR gene expression and protein levels are upregulated, and the functional response to beta(3)-AR stimulation is increased. This may contribute to progression of cardiac dysfunction in CHF.
- Published
- 2001
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