Norepinephrine clearance is increased during acute hypoxemia in humans

Urs Leuenberger, K. Gleeson, K. Wroblewski, S. Prophet, Robert Zelis, C. Zwillich, Lawrence Sinoway

Research output: Contribution to journalArticle

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Abstract

Acute hypoxemia leads to activation of the sympathetic nervous system (SNS), yet adrenergic vasoconstriction does not occur and venous plasma norepinephrine (NE) fails to rise as expected. To examine whether this dissociation between SNS tone and plasma NE is due to altered metabolism of NE, we measured arterial NE kinetics ([3H]NE infusion technique) and sympathetic nervous outflow to muscle (peroneal microneurography) during 25-30 min of hypoxemia (spontaneous breathing, mean O2 saturation 74%) in six healthy young men. During hypoxemia, muscle sympathetic nervous activity (MSNA) rose significantly from 12.2 ± 3.3 to 18.6 ± 3.5 bursts/min, and the total amplitude increased from 123 ± 36 to 225 ± 50 mm/min. NE spillover, an index of NE release at the sympathetic nerve terminals, rose from 1.66 ± 0.30 to 2.33 ± 0.40 nmol·min-1·m-2 (P = 0.014). However, NE clearance increased also from 0.99 ± 0.05 to 1.19 ± 0.11 l·min-1·m-2 (P = 0.014), and arterial NE rose from 281 ± 50 to 339 ± 64 pg/ml (P = 0.023). Hypoxemia resulted in a significant rise in forearm blood flow and a decrease in forearm vascular resistance. The fact that skin blood flow and vascular resistance did not change implies that forearm vasodilation was localized to skeletal muscle. Our results suggest that during acute hypoxemia in humans the SNS is activated but the rise in plasma NE is attenuated because NE clearance is increased.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume261
Issue number5 30-5
StatePublished - Dec 1 1991

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Norepinephrine
Sympathetic Nervous System
Forearm
Vascular Resistance
Hypoxia
Muscles
Vasoconstriction
Vasodilation
Adrenergic Agents
Respiration
Skeletal Muscle
Skin

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Cite this

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title = "Norepinephrine clearance is increased during acute hypoxemia in humans",
abstract = "Acute hypoxemia leads to activation of the sympathetic nervous system (SNS), yet adrenergic vasoconstriction does not occur and venous plasma norepinephrine (NE) fails to rise as expected. To examine whether this dissociation between SNS tone and plasma NE is due to altered metabolism of NE, we measured arterial NE kinetics ([3H]NE infusion technique) and sympathetic nervous outflow to muscle (peroneal microneurography) during 25-30 min of hypoxemia (spontaneous breathing, mean O2 saturation 74{\%}) in six healthy young men. During hypoxemia, muscle sympathetic nervous activity (MSNA) rose significantly from 12.2 ± 3.3 to 18.6 ± 3.5 bursts/min, and the total amplitude increased from 123 ± 36 to 225 ± 50 mm/min. NE spillover, an index of NE release at the sympathetic nerve terminals, rose from 1.66 ± 0.30 to 2.33 ± 0.40 nmol·min-1·m-2 (P = 0.014). However, NE clearance increased also from 0.99 ± 0.05 to 1.19 ± 0.11 l·min-1·m-2 (P = 0.014), and arterial NE rose from 281 ± 50 to 339 ± 64 pg/ml (P = 0.023). Hypoxemia resulted in a significant rise in forearm blood flow and a decrease in forearm vascular resistance. The fact that skin blood flow and vascular resistance did not change implies that forearm vasodilation was localized to skeletal muscle. Our results suggest that during acute hypoxemia in humans the SNS is activated but the rise in plasma NE is attenuated because NE clearance is increased.",
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Norepinephrine clearance is increased during acute hypoxemia in humans. / Leuenberger, Urs; Gleeson, K.; Wroblewski, K.; Prophet, S.; Zelis, Robert; Zwillich, C.; Sinoway, Lawrence.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 261, No. 5 30-5, 01.12.1991.

Research output: Contribution to journalArticle

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T1 - Norepinephrine clearance is increased during acute hypoxemia in humans

AU - Leuenberger, Urs

AU - Gleeson, K.

AU - Wroblewski, K.

AU - Prophet, S.

AU - Zelis, Robert

AU - Zwillich, C.

AU - Sinoway, Lawrence

PY - 1991/12/1

Y1 - 1991/12/1

N2 - Acute hypoxemia leads to activation of the sympathetic nervous system (SNS), yet adrenergic vasoconstriction does not occur and venous plasma norepinephrine (NE) fails to rise as expected. To examine whether this dissociation between SNS tone and plasma NE is due to altered metabolism of NE, we measured arterial NE kinetics ([3H]NE infusion technique) and sympathetic nervous outflow to muscle (peroneal microneurography) during 25-30 min of hypoxemia (spontaneous breathing, mean O2 saturation 74%) in six healthy young men. During hypoxemia, muscle sympathetic nervous activity (MSNA) rose significantly from 12.2 ± 3.3 to 18.6 ± 3.5 bursts/min, and the total amplitude increased from 123 ± 36 to 225 ± 50 mm/min. NE spillover, an index of NE release at the sympathetic nerve terminals, rose from 1.66 ± 0.30 to 2.33 ± 0.40 nmol·min-1·m-2 (P = 0.014). However, NE clearance increased also from 0.99 ± 0.05 to 1.19 ± 0.11 l·min-1·m-2 (P = 0.014), and arterial NE rose from 281 ± 50 to 339 ± 64 pg/ml (P = 0.023). Hypoxemia resulted in a significant rise in forearm blood flow and a decrease in forearm vascular resistance. The fact that skin blood flow and vascular resistance did not change implies that forearm vasodilation was localized to skeletal muscle. Our results suggest that during acute hypoxemia in humans the SNS is activated but the rise in plasma NE is attenuated because NE clearance is increased.

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