title: Attenuated muscle metaboreflex-induced increases in cardiac function in hypertension.
abstract: Sympathoactivation may be excessive during exercise in subjects with hypertension, leading to increased susceptibility to adverse cardiovascular events, including arrhythmias, infarction, stroke, and sudden cardiac death. The muscle metaboreflex is a powerful cardiovascular reflex capable of eliciting marked increases in sympathetic activity during exercise. We used conscious, chronically instrumented dogs trained to run on a motor-driven treadmill to investigate the effects of hypertension on the mechanisms of the muscle metaboreflex. Experiments were performed before and 30.9 ± 4.2 days after induction of hypertension, which was induced via partial, unilateral renal artery occlusion. After induction of hypertension, resting mean arterial pressure was significantly elevated from 98.2 ± 2.6 to 141.9 ± 7.4 mmHg. The hypertension was caused by elevated total peripheral resistance. Although cardiac output was not significantly different at rest or during exercise after induction of hypertension, the rise in cardiac output with muscle metaboreflex activation was significantly reduced in hypertension. Metaboreflex-induced increases in left ventricular function were also depressed. These attenuated cardiac responses caused a smaller metaboreflex-induced rise in mean arterial pressure. We conclude that the ability of the muscle metaboreflex to elicit increases in cardiac function is impaired in hypertension, which may contribute to exercise intolerance.
authors.affiliation: Department of Physiology and The Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Sala-Mercado
authors.forename: Marty D
authors.initials: MD
authors.lastname: Spranger
authors.forename: Rania
authors.initials: R
authors.lastname: Abu-Hamdah
authors.forename: Jasdeep
authors.initials: J
authors.lastname: Kaur
authors.forename: Matthew
authors.initials: M
authors.lastname: Coutsos
authors.forename: Douglas
authors.initials: D
authors.lastname: Stayer
authors.forename: Robert A
authors.initials: RA
authors.lastname: Augustyniak
authors.forename: Donal S
authors.initials: DS
authors.lastname: O'Leary
mesh_terms: D000818:Animals; D062186:Arterial Pressure; D002302:Cardiac Output; D004195:Disease Models, Animal; D004285:Dogs; D017079:Exercise Tolerance; D005260:Female; D006321:Heart / Q000294:innervation*; D006439:Hemodynamics; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism; D009200:Myocardial Contraction; D005082:Physical Exertion; D012018:Reflex; D012420:Running; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors; D014655:Vascular Resistance; D016277:Ventricular Function, Left
keywords: arterial pressure; ergoreceptors; exercise; pressor response; vasoconstriction