DEVELOPMENTAL DIFFERENCES IN CATALASE ACTIVITY AND HYPOXIC-HYPEROXIC EFFECTS ON FLUID BALANCE IN ISOLATED LAMB LUNGS

The effects of hypoxia (95% N2/5% CO2) followed by hyperoxia (95% O2/5 % CO2) were determined in isolated lungs of premature (gestational age 128 to 135 d) and full-term (postnatal age 0 to 5 d) lambs perfused w ith autologous blood (100 mL . min-1 . kg body weight-1). In full-term lungs, hypoxia-hyperoxia compared with hypoxia alone decreased pulmon ary artery pressure and increased weight gain and extravascular lung w ater. In premature lungs, the increase in weight gain was greater and was associated with hemorrhage and increased pulmonary arterial and pe ak airway pressures. Papaverine eliminated reoxygenation-induced diffe rences in pulmonary artery pressure, peak airway pressure, and weight gain in both age groups. Osmotic reflection coefficients for total pro tein and albumin, measured by a modification of the filtered volume te chnique, averaged 0.591 +/- 0.054 (SEM) and 0.465 +/- 0.054 (SEM), res pectively, and were not altered by reoxygenation or age. Catalase acti vity in lung tissue and erythrocytes was lower in premature lambs, but there were no age-related differences in superoxide dismutase or glut athione peroxidase activities. These results demonstrate that hypoxia- hyperoxia in isolated lamb lungs increased lung weight due to edema fo rmation in full-term lamb lungs and hemorrhage in premature lamb lungs and that this increase was greater in premature lamb lungs. We specul ate that the weight gain caused by reoxygenation was due to a vasodila tion-induced increase in surface area in full-term lamb lungs and a va soconstriction-induced increase in vascular pressure in premature lamb lungs. The mediators of this developmental difference in vasomotor to ne are unknown, but lower catalase activity in premature lungs suggest s that hydrogen peroxide may have played a role.