ACUTE ALVEOLAR HYPOXIA INCREASES BLOOD-TO-TISSUE ALBUMIN TRANSPORT - ROLE OF ATRIAL-NATRIURETIC-PEPTIDE

Plasma immunoreactive atrial natriuretic peptide (irANP) and blood-to- tissue clearance of I-131-labeled rat serum albumin (C-RSA) were exami ned in anesthetized rats during hypoxic ventilation (n = 5-7/group). H ypoxia (10 min) increased irANP from 211 +/- 29 (room air) to 229 +/- 28 (15% O-2, not significant), 911 +/- 205 (10% O-2), and 4,374 +/- 96 1 pg/ml (8% O-2), respectively. Graded increases in C-RSA were signifi cant at 8% O-2 in fat (3.6-fold), ileum (2.2-fold), abdominal muscles (2.0-fold), kidney (1.8-fold), and jejunum (1.4-fold). C-RSA was decre ased in back skin and testes; heart, brain, and lungs were unaffected. The increases in C-RSA were related to irANP and not to arterial PO2. Circulating plasma volume was negatively correlated with whole body C -RSA. Graded increases in extravascular water content (EVW) were found in the kidney, left heart, and cerebrum and were positively related t o C-RSA in the kidney. EVW decreased in gastrointestinal tissues; the magnitude was inversely related to C-RSA. We conclude that ANP-induced protein extravasation contributes to plasma volume contraction during acute hypoxia.