Hypoxia-induced ANP secretion in subjects susceptible to high-altitude pulmonary edema

We investigated the effects of acute hypoxia (10% O2) on plasma level of atrial natriuretic peptide (ANP) and pulmonary hemodynamics in five subjects with a history of high-altitude pulmonary edema (HAPE). Plasma renin activity and plasma levels of aldosterone, epinephrine and norepinephrine were also measured. The plasma ANP levels in HAPE-susceptible subjects rose significantly in response to 10% O2 (from 34.8 +/- 5.4 to 51.4 +/- 7.3 pg.ml-1; P less than 0.05), not associated with any increase in either atrial pressure. Compared with six control subjects, the rise of ANP level was greater in HAPE-susceptible subjects (16.6 +/- 4.4 vs 3.9 +/- 1.2 pg.ml-1; P less than 0.05). There was a significant positive correlation between the rise of ANP level and the increase of pulmonary arterial pressure. No significant difference was observed in any of other hormonal responses to acute hypoxia between the two groups. We interpret these results as indicating that the ANP secretory response to acute hypoxia in HAPE-susceptible subjects, which is not mediated by an increase in atrial pressure, may be greater than that in nonsusceptible subjects in association with a greater pressor response of pulmonary circulation.