Women at altitude: Forearm hemodynamics during acclimatization to 4,300 m with α 1 -adrenergic blockade

Stacy Zamudio, Matthew Douglas, Robert S. Mazzeo, Eugene E. Wolfel, David A. Young, Paul Rock, Barry Braun, Stephen R. Muza, Gail E. Butterfield, Lorna G. Moore

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Abstract

We hypothesized that blockade of α 1 -adrenergic receptors would prevent the rise in peripheral vascular resistance that normally occurs during acclimatization. Sixteen eumenorrheic women were studied at sea level (SL) and at 4,300 m (days 3 and 10). Volunteers were randomly assigned to take the selective α 1 -blocker prazosin or placebo. Venous compliance, forearm vascular resistance, and blood flow were measured using plethysmography. Venous compliance fell by day 3 in all subjects (1.39 ± 0.30 vs. 1.62 ± 0.43 ml·Δ30 mmHg -1 ·100 ml tissue -1 ·min -1 at SL, means ± SD). Altitude interacted with prazosin treatment (P < 0.0001) such that compliance returned to SL values by day 10 in the prazosin-treated group (1.68 ÷± 0.19) but not in the placebo-treated group (1.20 ± 0.10, P < 0.05). By day 3 at 4,300 m, all women had significant falls in resistance (35.2 ± 13.2 vs. 54.5 ± 16.1 mmHg·ml -1 ·min -1 at SL) and rises in blood flow (2.5 ± 1.0 vs. 1.6 ± 0.5 ml·100 ml tissue -1 ·min -1 at SL). By day 10, resistance and flow returned toward SL, but this return was less in the prazosin-treated group (resistance: 39.8 ± 4.6 mmHg·ml -1 ·min -1 with prazosin vs. 58.5 ± 9.8 mmHg·ml -1 ·min -1 with placebo; flow: 1.9 ± 0.7 ml·100 ml tissue -1 ·min -1 with prazosin vs. 2.3 ± 0.3 ml·100 ml tissue -1 ·min -1 with placebo, P < 0.05). Lower resistance related to higher circulating epinephrine in both groups (r = -0.50, P < 0.0001). Higher circulating norepinephrine related to lower venous compliance in the placebo-treated group (r = -0.42, P < 0.05). We conclude that α 1 -adrenergic stimulation modulates peripheral vascular changes during acclimatization.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume281
Issue number6 50-6
StatePublished - 1 Dec 2001

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Keywords

  • Epinephrine
  • High altitude
  • Hypoxia
  • Neropinephrine
  • Peripheral blood flow
  • Prazosin
  • Vascular resistance
  • Venous compliance

Cite this

Zamudio, S., Douglas, M., Mazzeo, R. S., Wolfel, E. E., Young, D. A., Rock, P., Braun, B., Muza, S. R., Butterfield, G. E., & Moore, L. G. (2001). Women at altitude: Forearm hemodynamics during acclimatization to 4,300 m with α 1 -adrenergic blockade. American Journal of Physiology - Heart and Circulatory Physiology, 281(6 50-6).