Effect of beta-adrenoceptor blockade on renin-aldosterone and alpha-ANF during exercise at altitude.
The renin-aldosterone system may be depressed in subjects exercising at high altitude, thereby preventing excessive angiotensin I (ANG I) and aldosterone levels, which could favor the onset of acute mountain sickness. The role of beta-adrenoceptors in hormonal responses to hypoxia was investigated in 12 subjects treated with a nonselective beta-blocker, pindolol. The subjects performed a standardized maximal bicycle ergometer exercise with (P) and without (C) acute pindolol treatment (15 mg/day) at sea level, as well as during a 5-day period at high altitude (4,350 m, barometric pressure 450 mmHg). During sea-level exercise, pindolol caused a reduction in plasma renin activity (PRA, 2.83 +/- 0.35 vs. 5.13 +/- 0.7 ng ANG I.ml-1.h-1, P less than 0.01), an increase in plasma alpha-atrial natriuretic factor (alpha-ANF) level (23.1 +/- 2.9 (P) vs. 10.4 +/- 1.5 (C) pmol/1, P less than 0.01), and no change in plasma aldosterone concentration [0.50 +/- 0.04 (P) vs. 0.53 +/- 0.03 (C) nmol/1]. Compared with sea-level values, PRA (3.45 +/- 0.7 ng ANG I.ml-1.h-1) and PA (0.39 +/- 0.03 nmol/1) were significantly lower (P less than 0.05) during exercise at high altitude. alpha-ANF was not affected by hypoxia. When beta-blockade was achieved at high altitude, exercise-induced elevation in PRA was completely abolished, but no additional decline in PA occurred. Plasma norepinephrine and epinephrine concentrations tended to be lower during maximal exercise at altitude; however, these differences were not statistically significant. Our results provide further evidence that hypoxia has a suppressive effect on the renin-aldosterone system. However, beta-adrenergic mechanisms do not appear to be responsible for inhibition of renin secretion at high altitude.
Bouissou
P
P
ARPE Faculté de Médecine Créteil, Institut National de la Santé et de la Recherche Médicale U296, Paris, France.
Richalet
J P
JP
Galen
F X
FX
Lartigue
M
M
Larmignat
P
P
Devaux
F
F
Dubray
C
C
Keromes
A
A
D000328:Adult; D000450:Aldosterone / Q000097:blood*; D000531:Altitude; D009320:Atrial Natriuretic Factor / Q000097:blood*; D004837:Epinephrine / Q000097:blood; D015444:Exercise; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010869:Pindolol / Q000494:pharmacology*; D012083:Renin / Q000097:blood*; D012084:Renin-Angiotensin System / Q000187:drug effects*
D000450:Aldosterone; D009320:Atrial Natriuretic Factor; D010869:Pindolol; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine