Journal
HYPERTENSION
Volume 35, Issue 5, Pages 1124-1128Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/01.HYP.35.5.1124
Keywords
microdialysis; adenosine; muscle, skeletal; exercise; lactates
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Funding
- NCRR NIH HHS [RR-00095] Funding Source: Medline
- NHLBI NIH HHS [HL-56693] Funding Source: Medline
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It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise presser reflex. Furthermore, exo,exogenous adenosine induces sympathetic activation that mimics the exercise presser reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292+/-0.058 mu mol/L, n=4) by pel-fusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Muscle interstitial adenosine concentrations increased from 0.23+/-0.04 to 0.82+/-0.14 mu mol/L (n=14, P<0.001) during intermittent dynamic exercise at 50% of maximal voluntary contraction. Lactate increased from 0.8+/-0.1 to 2.3+/-0.3 mmol/L (P<0.001). Lower intensity (15% maximal voluntary contraction) intermittent dynamic exercise increased adenosine concentrations from 0.104+/-0.02 to 0.42+/-0.16 mu mol/L (n=7). The addition of ischemia to this low level of exercise produced a greater increase in adenosine (from 0.095+/-0.02 to 0.48+/-0.2 mu mol/L) compared with nonischemic exercise (0.095+/-0.02 to 0.25+/-0.12 mu mol/L). These results indicate that microdialysis is useful in estimating adenosine concentrations and in reflecting changes in muscle interstitial adenosine during dynamic exercise in humans.
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