Hormonal changes in normal and polycythemic high altitude
natives.
Antezana, Ana Maria, Jean Paul Richalet, Irma Noriega, Mario Galarza,
and Gerardo Antezana.
Association pour la Recherche en Physiologie de l'Environnement
(A.R.P.E), Bobigny France and Instituto Boliviano de Biologia de
Altura (I.B.B.A) La Paz Bolivia
APStracts 2:0249A, 1995.
Acute and chronic exposure to high altitude (HA) hypoxia inhibits the
renin angiotensin aldosterone system and may modify the release of
atrial natriuretic peptide in sea level natives. In HA natives the
release of these hormones could be influenced by changes in blood
volume or pulmonary arterial pressure. Twenty four men residing in La
Paz at 3,600m were separated either into two groups: one
normocythemic (HAN, with hematocrit <57%, n=13), and the other
polycythemic (HAP, with hematocrit >57%, n=11). A control group
of 9 sea level (SL) residents was studied in normoxia (SLN), as well
as after 4 days spent at 4,350m (SLH). The groups were tested for
plasma active renin (PAR), plasma aldosterone concentration (PAC),
atrial natriuretic peptide (ANP), potassium and norepineprine
concentrations at rest and after a maximal exercise. Pulmonary
arterial systolic pressure was assessed by a Doppler technique. It
was observed that PAR and PAC at rest and after exercise were lower
in the SLH than in the SLN. PAR and norepineprine concentration were
higher among highlanders, than in SLN. Renin response to exercise was
normal among HAN, slightly decreased among HAP, and exercise-induced
increase in aldosterone was attenuated in both HA groups. Aldosterone
response to renin was maintained among the SLH, but was attenuated in
HA groups possibly owing to a protective mechanism against salt and
water retention. Resting and exercise ANP was lower in high altitude
groups than in SLN. In HAP, a positive relationship was found between
ANP and pulmonary arterial pressure at rest. Evidence of lower plasma
ANP in HA natives in spite of higher pulmonary pressure could be
explained by an adaptation to chronic distension of atrial stretch
receptors involved in central blood volume regulation.
Received 3 January 1995; accepted in final form 8 May 1995.
APS Manuscript Number A3-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.