Roles of nitric oxide and prostaglandins in the hyperemic response to a maximal metabolic stimulus: Redundancy prevails

Marcos G. Lopez, Bruno M. Silva, Michael J. Joyner, Darren P. Casey

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Vasodilatory mechanisms controlling post-exercise or post-ischemic hyperemia are thought to be under redundant control and remain incompletely understood. A maximal metabolic stimulus evoked by ischemic exercise (IE) might limit redundancy by full activation of multiple pathways. We tested whether nitric oxide (NO) and/or prostaglandins contribute to the hyperemic response to IE. 17 subjects were randomized into two groups and performed three trials of IE during control (saline), N G-monomethyl-l-arginine (l-NMMA; NOS inhibition) (protocol 1) or ketorolac (cyclooxygenase inhibition) infusion (protocol 2), and combined l-NMMA/ketorolac infusion via a brachial arterial catheter. Forearm blood flow (FBF) was measured with venous occlusion plethysmography following IE trials consisting of 5 min of ischemia and simultaneous rhythmic handgrip exercise (final 2 min). Peak and total (area under the curve) FBF and blood pressure (MAP) were measured for 3 min after each trial. Forearm vascular conductance (FVC) was calculated as FBF/MAP. Change (Δ) in peak FBF and FVC from baseline differed only between peak FBF for the saline and l-NMMA + ketorolac trials in protocol 1. Peak ΔFBF was 26.8 ± 2.5, 30.0 ± 2.8, and 33.9 ± 3.6 ml 100 ml-1 min-1 for saline, l-NMMA, and l-NMMA + ketorolac trials (P = 0.04). For protocol 1 (n = 8), total ΔFVC was 59.6 ± 4.3, 57.8 ± 6.0, and 59.9 ± 5.6 ml 100 ml-1 100 mmHg-1 for saline, l-NMMA, and l-NMMA + ketorolac trials, (P = 0.82). For protocol 2 (n = 9), total ΔFVC was 54.2 ± 5.0, 56.9 ± 4.5, and 56.5 ± 5.3 ml 100 ml-1 100 mmHg-1 for saline, ketorolac, and ketorolac + l-NMMA trials, (P = 0.69). These results suggest that NO and PGs are not obligatory for the hyperemic response to IE, and other vasodilator mechanisms predominate.

Original languageEnglish (US)
Pages (from-to)1449-1456
Number of pages8
JournalEuropean Journal of Applied Physiology
Volume113
Issue number6
DOIs
StatePublished - Jun 1 2013

Keywords

  • Hyperemia
  • Ischemia
  • Nitric oxide
  • Prostaglandins
  • Vasodilation

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)

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