Adenosine contributes to hypoxia-induced forearm vasodilation in humans

Urs Leuenberger, Kris Gray, Michael D. Herr

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

In humans, hypoxia leads to increased sympathetic neural outflow to skeletal muscle. However, blood flow increases in the forearm. The mechanism of hypoxia-induced vasodilation is unknown. To test whether hypoxia-induced vasodilation is cholinergically mediated or is due to local release of adenosine, normal subjects were studied before and during acute hypoxia (inspired O2 10.5%; ~20 min). In experiment I, aminophylline (50-200 μg·min-1·100 ml forearm tissue-1) was infused into the brachial artery to block adenosine receptors (n = 9). In experiment H, cholinergic vasodilation was blocked by atropine (0.4 mg over 4 min) infused into the brachial artery (n = 8). The responses of forearm blood flow (plethysmography) and forearm vascular resistance to hypoxia in the infused and opposite (control) forearms were compared. During hypoxia (arterial O2 saturation 77 ± 2%), minute ventilation and heart rate increased while arterial pressure remained unchanged; forearm blood flow rose by 35 ± 6% in the control forearm but only by 5 ± 8% in the aminophylline-treated forearm (P < 0.02). Accordingly, forearm vascular resistance decreased by 29 ± 5% in the control forearm but only by 9 ± 6% in the aminophylline-treated forearm (P < 0.02). Atropine did not attenuate forearm vasodilation during hypoxia. These data suggest that adenosine contributes to hypoxia-induced vasodilation, whereas cholinergic vasodilation does not play a role.

Original languageEnglish (US)
Pages (from-to)2218-2224
Number of pages7
JournalJournal of Applied Physiology
Volume87
Issue number6
StatePublished - Jan 1 1999

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Forearm
Vasodilation
Adenosine
Aminophylline
Brachial Artery
Atropine
Vascular Resistance
Cholinergic Agents
Hypoxia
Purinergic P1 Receptors
Plethysmography
Ventilation
Arterial Pressure
Skeletal Muscle
Heart Rate

All Science Journal Classification (ASJC) codes

  • Physiology
  • Physiology (medical)

Cite this

Leuenberger, Urs ; Gray, Kris ; Herr, Michael D. / Adenosine contributes to hypoxia-induced forearm vasodilation in humans. In: Journal of Applied Physiology. 1999 ; Vol. 87, No. 6. pp. 2218-2224.
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Adenosine contributes to hypoxia-induced forearm vasodilation in humans. / Leuenberger, Urs; Gray, Kris; Herr, Michael D.

In: Journal of Applied Physiology, Vol. 87, No. 6, 01.01.1999, p. 2218-2224.

Research output: Contribution to journalArticle

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N2 - In humans, hypoxia leads to increased sympathetic neural outflow to skeletal muscle. However, blood flow increases in the forearm. The mechanism of hypoxia-induced vasodilation is unknown. To test whether hypoxia-induced vasodilation is cholinergically mediated or is due to local release of adenosine, normal subjects were studied before and during acute hypoxia (inspired O2 10.5%; ~20 min). In experiment I, aminophylline (50-200 μg·min-1·100 ml forearm tissue-1) was infused into the brachial artery to block adenosine receptors (n = 9). In experiment H, cholinergic vasodilation was blocked by atropine (0.4 mg over 4 min) infused into the brachial artery (n = 8). The responses of forearm blood flow (plethysmography) and forearm vascular resistance to hypoxia in the infused and opposite (control) forearms were compared. During hypoxia (arterial O2 saturation 77 ± 2%), minute ventilation and heart rate increased while arterial pressure remained unchanged; forearm blood flow rose by 35 ± 6% in the control forearm but only by 5 ± 8% in the aminophylline-treated forearm (P < 0.02). Accordingly, forearm vascular resistance decreased by 29 ± 5% in the control forearm but only by 9 ± 6% in the aminophylline-treated forearm (P < 0.02). Atropine did not attenuate forearm vasodilation during hypoxia. These data suggest that adenosine contributes to hypoxia-induced vasodilation, whereas cholinergic vasodilation does not play a role.

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