Vol. 281, Issue 6, H2636-H2644, December 2001
Women at altitude: forearm hemodynamics during
acclimatization to 4,300 m with 
1-adrenergic
blockade
Stacy
Zamudio1,2,5,
Matthew
Douglas2,
Robert S.
Mazzeo6,
Eugene E.
Wolfel3,
David A.
Young4,
Paul B.
Rock8,
Barry
Braun7,
Stephen R.
Muza8,
Gail E.
Butterfield7,
, and
Lorna G.
Moore1,5
1 Women's Health Research Center and 2 Departments
of Anesthesiology, 3 Cardiology, and 4 Preventive
Medicine and Biometrics, University of Colorado Health Sciences Center,
Denver 80262; 5 Department of Anthropology, University of
Colorado at Denver, Denver 80217-3364; 6 Department of
Kinesiology and Applied Physiology, University of Colorado at Boulder,
Boulder, Colorado 80309; 7 Aging Study Unit, Geriatric Research
Education and Clinical Center, Veterans Affairs Palo Alto Health
Services, Palo Alto, California 94304; and 8 Thermal and
Mountain Medicine Division, United States Army Research Institute
of Environmental Medicine, Natick, Massachusetts 01760-5007
We
hypothesized that blockade of 
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
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 · 
30
mmHg
1 · 100 ml
tissue1 · min1 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 · ml1 · min1 at
SL) and rises in blood flow (2.5 ± 1.0 vs. 1.6 ± 0.5 ml · 100 ml tissue1 · min1
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 · ml1 · min1 with
prazosin vs. 58.5 ± 9.8 mmHg · ml1 · min1 with
placebo; flow: 1.9 ± 0.7 ml · 100 ml
tissue1 · min1 with prazosin vs.
2.3 ± 0.3 ml · 100 ml
tissue1 · min1 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 1-adrenergic stimulation modulates peripheral
vascular changes during acclimatization.
high altitude; hypoxia; venous compliance; peripheral blood flow; vascular resistance; prazosin; norepinephrine; epinephrine
Deceased 28 December 1999.
