Oxyntomodulin increases intrinsic heart rate through the glucagon receptor. Issue 5 (20th October 2013)

• Record Type: Journal Article
• Authors: Mukharji, Auyon; Drucker, Daniel J.; Charron, Maureen J.; Swoap, Steven J.
• Is Part Of: Physiological reports. Volume 1:Issue 5(2013:Oct.)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-10-20
• Subjects: Beta block -- GLP‐1 -- OXM -- sympathetic nervous system; Physiology -- Periodicals; 571
• DOI: 10.1002/phy2.112
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Two hormones from the gastrointestinal tract, glucagon and oxyntomodulin (OXM), vigorously elevate the intrinsic heart rate (IHR ) of mice. We have previously shown that OXM influences murine heart rate (HR) independent of the glucagon‐like peptide 1 (GLP‐1) receptor. Here, we demonstrate using radiotelemetry in mice deficient in the glucagon receptor ( Gcgr −/−) that both OXM and glucagon require the glucagon receptor for their chronotropic effects on the heart. Furthermore, we found that other hormones associated with hunger and satiety (ghrelin, leptin, and PYY3‐36 ) had no effect on IHR, while cholecystokinin moderately elevated the IHR . Finally, the resting HR of Gcgr −/− mice was higher than in control mice ( Gcgr +/+ and Gcgr +/−) at thermal neutral temperature (30°C). Using atropine, we demonstrated that Gcgr −/− mice have diminished parasympathetic (PNS) influence of the heart at this temperature. Gcgr −/− mice displayed a normal bradycardia as compared to controls in response to administration of either methacholine (to activate the muscarinic acetylcholine receptor) or methoxamine (to activate the baroreflex through agonism of the α1 adrenergic receptor agonist) suggesting that vagal pathways are intact in the Gcgr −/− mice. As OXM is an agonist of the GLP‐1 receptor and Gcgr with antidiabetic activity, we suggest OXM may be an alternative to glucagon in the treatment of overdose of beta‐blockers to elevate HR in clinical conditions. Abstract : e00112 Abstract : Oxyntomodulin (OXM), a gut‐derived peptide hormone, elicits many of its actions through the glucagon‐like peptide 1 (GLP‐1) receptor. We show here, however, that OXM vigorously increases the murine intrinsic heart rate via the glucagon receptor using Gcgr −/− mice, and further suggest that OXM be considered an alternative to glucagon in the treatment to elevate heart rate in human patients that have cardiotoxicity associated with an overdose of beta‐blockers or calcium channel blockers.