Electrophysiological evaluation of the beta-blocking properties and direct membrane effects of l-moprolol and its enantiomer d-moprolol.
The electrophysiological and beta-blocking properties of l- and d-moprolol have been studied in sheep cardiac Purkinje fibers. l-Moprolol (0.3-100 nM) dose-dependently antagonized the inotropic (ED50 = 1.2 +/- 0.4 nM) and chronotropic (ED50 = 5.8 +/- 0.6 nM) effects of isoprenaline. d-Moprolol (0.3-100 nM) was fully devoid of beta-blocking properties under the same experimental conditions. Both isomers had the same electrophysiological profile: they did not influence action potential characteristics, contractility and normal automaticity up to 1 microM. On the whole, l-moprolol appears to be a potent beta-blocker, exerting membrane depressant effects only at a concentration 2000 times higher than those exerting effective beta-blockade.
Porciatti
F
F
Department of Clinical and Preclinical Pharmacology, University of Florence, Italy.
Cerbai
E
E
Masini
I
I
Mugelli
A
A
D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects / Q000294:innervation; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D050198:Phenoxypropanolamines; D011189:Potassium Chloride / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology*; D011690:Purkinje Fibers / Q000187:drug effects; D012756:Sheep; D013237:Stereoisomerism
D000319:Adrenergic beta-Antagonists; D050198:Phenoxypropanolamines; D011412:Propanolamines; D011189:Potassium Chloride; C009976:moprolol