Does chronic beta 1-adrenoceptor antagonist treatment alter right atrial beta-adrenoceptor and muscarinic M2-receptor number and functional responsiveness in patients undergoing coronary artery bypass grafting?
Chronic beta-1 blockade induces complex receptor adaptations in the human atrium, including beta-2 sensitization and M2-muscarinic desensitization, which may affect cardiac responsiveness.
In 64 patients undergoing coronary artery bypass grafting the effects of chronic beta 1-adrenoceptor antagonist (metoprolol, atenolol, bisoprolol) treatment on right atrial beta-adrenoceptor and muscarinic M2-receptor number and functional responsiveness were investigated. 2. The beta 1-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor number, did not affect beta 2-adrenoceptor number, and decreased muscarinic M2-receptor number. 3. Concomitantly, activation of right atrial adenylate cyclase by 10 microM GTP, 10 microM isoprenaline and 1 microM forskolin was enhanced and inhibition by 100 microM carbachol was diminished. 4. On isolated, electrically driven right atria the beta 1-adrenoceptor-mediated positive inotropic effect of noradrenaline was - even with beta 1-adrenoceptor number increased - not altered, while the beta 2-adrenoceptor-mediated effect of procaterol was markedly enhanced. However, the carbachol-induced negative inotropic effect was decreased. 5. It is concluded that chronic beta 1-adrenoceptor antagonist treatment increases beta 1-adrenoceptor number and concomitantly sensitizes beta 2-adrenoceptor function, but desensitizes muscarinic M2-receptor function in the human heart.
Motomura et al. (Mon,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: