Effects of (+/-)- (+)- and (-)-metoprolol, (+/-)- (+)- and (-)-pindolol, (+/-)-mepindolol and (+/-)-bopindolol on the rat left atria and portal vein.
1. The effects of (+/-)- (+)- and (-)-metoprolol, (+/-)- (+)- and (-)-pindolol, (+/-)-mepindolol and (+/-)-bopindolol on the beta 1-adrenoceptor mediated responses of the rat left atria and the beta 2-adrenoceptor mediated responses of the rat portal vein to isoprenaline have been determined. 2. Racemic and (-)-metoprolol were selective beta 1-adrenoceptor antagonists. (+)-Metoprolol was devoid of beta-adrenoceptor antagonistic activity. 3. Racemic and (-)-pindolol were potent and (+)-pindolol was a modest beta-adrenoceptor antagonist. 4. (+/-)-Mepindolol and (+/-)-bopindolol were apparently competitive antagonists of the isoprenaline beta 1-adrenoceptor mediated responses of the rat left atria but non-competitive antagonists of the isoprenaline beta 2-adrenoceptor mediated responses of the rat portal vein. 5. It is suggested that (+/-)-mepindolol and (+/-)-bopindolol are slowly dissociating beta-adrenoceptor antagonists and the non-competitive antagonism can only be detected on tissues with modest receptor reserves for maximum responses to isoprenaline.
Department of Pharmacology, School of Medicine, University of Auckland, New Zealand.
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Doggrell
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D016279:Atrial Function, Left / Q000187:drug effects; D004558:Electric Stimulation; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects; D010869:Pindolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011169:Portal Vein / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
D000319:Adrenergic beta-Antagonists; C015340:mepindolol; D010869:Pindolol; D008790:Metoprolol; C036007:bopindolol; D007545:Isoproterenol