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Effects of high‐altitude chronic hypoxia on platelet α 2 ‐receptors in man
Author(s) -
ZACCARIA M.,
BOREA P. A.,
OPOCHER G.,
PONCHIA A.,
VARANI K.,
FRACCAROLLO D.,
SCANDELLARI C.
Publication year - 1997
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1046/j.1365-2362.1997.1150663.x
Subject(s) - hypoxia (environmental) , effects of high altitude on humans , receptor , platelet , medicine , endocrinology , biology , chemistry , oxygen , anatomy , organic chemistry
During chronic high‐altitude (HA) exposure, basal and exercise‐induced noradrenaline (NA) increases do not parallel blood pressure (BP) changes observed; unlike β‐adrenergic receptors, to our knowledge no data are available on α‐receptors. We studied platelet α 2 ‐ and leucocyte β‐receptors and basal catecholamine levels in 11 trained climbers before and after they had spent a 15‐day period at a height of over 4400 m. In six of the climbers we also evaluated catecholamines after maximal bicycle ergometer exercise. After chronic high‐altitude exposure, a significant decrease was found in platelet α 2 ‐receptor density and affinity [ B max from 92.6 ± 6.7 to 54.6 ± 4.2 fmol mg −1 protein ( P < 0.001) and K D from 1.271 ± 0.034 to 1.724 ± 0.077 nmol L −1 ( P < 0.05)], although no changes to β‐receptors were observed. No changes were found in basal pre‐ and post‐expedition NA and adrenaline (A), and there was only a slight decrease in post‐expedition NA after maximal exercise. Our results suggest that prolonged exposure to hypoxia induces a down‐regulation of α 2 ‐receptors, which may be a contributory factor in the regulation of the physiological vascular response to acclimatization.