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 α2- 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 α2-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 α2-receptors, which may be a contributory factor in the regulation of the physiological vascular response to acclimatization.
|Number of pages||6|
|Journal||European Journal of Clinical Investigation|
|Publication status||Published - 1997|
- High altitude
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