Plasma volume contraction reduces atrial natriuretic peptide after four days of hypobaric hypoxia exposure

We investigated whether low arterial oxygen tension ([Formula: see text]) or hypoxia-induced plasma volume (PV) contraction, which reduces central blood (BV) and atrial distension, explain reduction in circulating natriuretic peptide (ANP) after prolonged hypoxic exposure. Ten healthy males were exposed for 4 days to hypobaric hypoxia corresponding an altitude of 3,500 m. PV changes determined by carbon monoxide rebreathing. Venous concentrations midregional proANP (MR-proANP) measured before at the end At latter time point, measurement was repeated 1) restoration [Formula: text] breathing a hyperoxic gas mixture 30 min 2) BV fluid infusion. Correspondingly, left ventricular end-diastolic (LVEDV), area (LAA), right (RAA) ultrasound exposure both infusion Hypoxic reduced MR-proANP from 37.9 ± 18.5 24.5 10.3 pmol/L ( P = 0.034), LVEDV 107.4 33.5 91.6 26.3 mL 0.005), LAA 15.8 4.9 13.3 4.2 cm 2 0.007), RAA 16.2 3.1 14.3 3.5 0.001). Hyperoxic did not affect (24.8 12.3 pmol/L, 0.890). Conversely, restored LVEDV, LAA, near-baseline values (108.0 29.3 mL, 17.2 5.7 , respectively, > 0.05 vs. baseline) increased 29.5 0.010 preinfusion 0.182 baseline). These findings support that ANP is least partially attributed whereas does seem contribute.