title: Selective regulation of beta 1- and beta 2-adrenoceptors in the human heart by chronic beta-adrenoceptor antagonist treatment.
abstract: 1. In 44 patients undergoing coronary artery bypass grafting, the effect of chronic administration of the beta-adrenoceptor antagonists sotalol, propranolol, pindolol, metoprolol and atenolol on beta-adrenoceptor density in right atria (containing 70% beta 1- and 30% beta 2-adrenoceptors) and in lymphocytes (having only beta 2-adrenoceptors) was studied. 2. beta-Adrenoceptor density in right atrial membranes and in intact lymphocytes was assessed by (-)-[125I]-iodocyanopindolol (ICYP) binding; the relative amount of right atrial beta 1- and beta 2-adrenoceptors was determined by inhibition of ICYP binding by the selective beta 2-adrenoceptor antagonist ICI 118,551 and analysis of the resulting competition curves by the iterative curve fitting programme LIGAND. 3. With the exception of pindolol, all beta-adrenoceptor antagonists increased right atrial beta-adrenoceptor density compared to that observed in atria from patients not treated with beta-adrenoceptor antagonists. 4. All beta-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor density; on the other hand, only sotalol and propranolol also increased right atrial beta 2-adrenoceptor density, whereas metoprolol and atenolol did not affect it and pindolol decreased it. 5. Similarly, in corresponding lymphocytes, only sotalol or propranolol increased beta 2-adrenoceptor density, while metoprolol and atenolol did not affect it and pindolol decreased it. 6. It is concluded that beta-adrenoceptor antagonists subtype-selectively regulate cardiac and lymphocyte beta-adrenoceptor subtypes. The selective increase in cardiac beta 1-adrenoceptor density evoked by metoprolol and atenolol may be one of the reasons for the beneficial effects observed in patients with end-stage congestive cardiomyopathy following intermittent treatment with low doses of selective beta 1-adrenoceptor antagonists.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D001667:Binding, Competitive; D001026:Coronary Artery Bypass; D005260:Female; D006321:Heart / Q000187:drug effects*; D006801:Humans; D008214:Lymphocytes / Q000032:analysis; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000145:classification / Q000187:drug effects*; D012984:Software
chemical_list: D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta