Beta2-adrenergic activation via administration of atenolol/formoterol combination increases contractility and coronary blood flow in isolated rat hearts

• Published in: Hellenic journal of cardiology Vol. 54; no. 5; pp. 341 - 347
• Main Authors: Watson, Dionysios C, Sargianou, Maria, Leivaditis, Vassilios, Anagnostopoulos, Constantinos
• Format: Journal Article
• Language: English
• Published: Netherlands 01.09.2013
• Subjects: Adrenergic beta-1 Receptor Antagonists - administration & dosage; Adrenergic beta-2 Receptor Agonists - administration & dosage; Animals; Atenolol - administration & dosage; Coronary Circulation - drug effects; Coronary Circulation - physiology; Drug Therapy, Combination; Ethanolamines - administration & dosage; Female; Formoterol Fumarate; Heart - drug effects; Heart Rate - drug effects; In Vitro Techniques; Myocardial Contraction - drug effects; Myocardial Contraction - physiology; Rats; Rats, Wistar; Receptors, Adrenergic, beta-2 - metabolism
• ISSN: 2241-5955

Commonly used adrenergic agonists in low cardiac output scenarios rely primarily on beta1adrenergic activation to stimulate cardiac function. Little is known about the use of beta2-adrenergic agonist administration for this purpose, although the associated vasodilation may be beneficial. This study was conducted in order to assess the efficacy of one such beta2-adrenergic agonist, formoterol, in augmenting cardiac function. The hearts of 8 anesthetized female Wistar rats were excised, and subsequently kept functional in an isolated heart preparation (Langendorff apparatus). After placement on the apparatus, hearts were subjected to the beta1-blocker, atenolol, and then to a combination of formoterol/atenolol. Left ventricular developed pressure (LVDP), heart rate (HR), and coronary flow (CF) were monitored. CF showed a median increase of 16% (p<0.05) after formoterol/atenolol administration, with this effect lasting 20 min post-administration. Furthermore, statistically significant differences included an early 26% increase in LVDP and a late 21% increase in HR. The CF increase was independent of HR and LVDP changes. Our results indicate that the beta2-agonist formoterol not only successfully increases heart rate and contractility, but also increases coronary flow, most likely by means of beta2-mediated coronary vasodilation. This pharmacological profile may prove to be especially beneficial in situations where cardiac output must be increased, while adequate myocardial oxygen delivery needs to be maintained.