Beta-adrenergic receptor desensitization in man: insight into post-exercise attenuation of cardiac function

Emma Hart, Ellen Dawson, Peter Rasmussen, Keith George, Niels H Secher, Greg Whyte, Rob Shave

Research output: Contribution to journalArticle (Academic Journal)peer-review

59 Citations (Scopus)

Abstract

Desensitization of the beta-adrenoreceptors (beta-AR) may contribute to a post-exercise reduction in left ventricular (LV) function. However, attenuation of the chronotropic and inotropic responses to a beta-AR agonist may depend upon alterations in parasympathetic tone. Furthermore, changes in cardiac output and LV diastolic function in response to a beta-AR agonist, pre- to post-prolonged exercise, remain unclear. Seven trained males (mean+/-s.d., age 27+/-6 years) performed 4 h of ergometer rowing. Peak heart rate (HR) and LV systolic and diastolic functional responses to incremental isoproterenol (isoprenaline) infusion (2, 4 and 6 microg kg min-1) were assessed after vagal blockade (glycopyrrolate, 1.2 mg). LV systolic function was assessed by the pressure/volume ratio (systolic blood pressure/end systolic volume) and , whilst diastolic function was evaluated as peak early and late transmitral filling velocities. Following exercise, the pressure/volume ratio decreased by 25% (P<0.05), whereas was unchanged (P>0.05). The early/late filling ratio was reduced by 36% after exercise, due to an elevation in late LV filling (P<0.01). The increase in HR response to isoproterenol infusion was blunted post-exercise at both 4 and 6 microg kg min-1 (127+/-7 and 132+/-6 beats min-1) compared with pre-exercise (138+/-8 and 141+/-12 beats min-1, P<0.05). Additionally, the pressure/volume ratio and were blunted post-exercise in response to isoproterenol (P<0.05). In contrast, diastolic function was similar before and after exercise during isoproterenol infusion (P>0.05). Desensitization of the beta-AR contributes to an attenuated left ventricular systolic but not diastolic function following prolonged exercise.

Original languageEnglish
Pages (from-to)717-25
Number of pages9
JournalJournal of Physiology
Volume577
Issue numberPt 2
DOIs
Publication statusPublished - 1 Dec 2006

Keywords

  • Adrenergic beta-Agonists
  • Adult
  • Cardiovascular Physiological Phenomena
  • Diastole
  • Exercise
  • Exercise Test
  • Glycopyrrolate
  • Heart Rate
  • Humans
  • Isoproterenol
  • Male
  • Muscarinic Antagonists
  • Myocardial Contraction
  • Receptors, Adrenergic, beta
  • Reference Values
  • Systole
  • Time Factors
  • Vagus Nerve
  • Ventricular Function, Left

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