Cardiotoxic effects of salmeterol in comparison with salbutamol on the isolated perfused Langendorff-heart of the rat.
beta 2-Adrenoceptor agonists used in the relief of bronchospasm have long been known to produce circulatory side-effects. Salmeterol (CAS 89365-50-4) is a novel long acting highly selective beta 2-agonist. We used the Langendorff-heart rat model (constant perfusion pressure) to compare the direct effects of salbutamol (CAS 18559-94-9, SAL) and salmeterol (SMT) on the cardiac performances and their toxic cardiac effects (induced by 3 mmol/l perfusate calcium). At the first step the concentration-effect curve was established for the maximal concentration (Cmax) of salbutamol leading to the maximal chronotropic effect on the heart for 20 min after a 20 min stabilization period (basal values). All hearts were consequently submitted to a 20 min Krebs-Henseleit perfusion in order to study the reversibility of the myocardial performances. The types of the myocardial and coronary beta-adrenoceptors involved in SAL (Cmax) effects were identified using a selective beta 1 (atenolol) and a beta 2 (butoxamine) antagonist. SAL induced an increase in the heart rate via a selective stimulation of the beta 1-adrenoceptors (beta 1-AR). SMT appeared to be more potent than SAL on the heart rate. Direct toxic drug effects on the heart appeared gradually with SAL whereas they appeared sharply at the highest concentration of SMT. The enzyme leakage observed during the recovery period was more pronounced with SMT than SAL. Perhaps, this phenomenon might be due to the lipophilicity of SMT. However, these direct cardiac effects of SMT have to be considered in association with its airway smooth muscle relaxant effect (therapeutic effect) which has been proven much more potent than those of SAL. Therefore SMT was less cardiotoxic than SAL at similar therapeutic concentrations.
Prévost
A
A
Département des Maladies Respiratoires, Centre Hospitalier Régional Universitaire de Reims, France.
Leperre
A
A
Moreau
F
F
Kantelip
J P
JP
Millart
H
H
D000318:Adrenergic beta-Agonists / Q000633:toxicity*; D000420:Albuterol / Q000031:analogs & derivatives* / Q000633:toxicity*; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D000068299:Salmeterol Xinafoate
D000318:Adrenergic beta-Agonists; D000068299:Salmeterol Xinafoate; D000420:Albuterol