This study examined the effects of lung collapse, a condition that causes relative hypoxia in lung tissues, on superoxide dismutase (SOD), cytochrome oxidase (cyt ox), and pyruvate kinase (py ki) activities in rabbits. Cyanide-insensitive respiration measurements were done in collapsed and contralateral lungs as an index of intracellular free radical production. Rabbits' right lungs were collapsed for 7 days after which the animals were killed. We found that control rabbit lungs contained ~25 SOD units/mg DNA measured with 10-5 M KCN (total SOD) and ~11 SOD units/mg DNA measured with 10-3 M KCN (mitochondrial or MnSOD). Right lung collapse caused a 25% decrease in mitochondrial SOD activity after 7 days (P < 0.05), whereas no significant changes occurred in right or left lungs' total SOD activity. In control rabbits cyt ox activity averaged ~0.009 μmol ferrocytochrome c · min-1 · mg DNA-1. Right lung collapse caused a >40% decrease in cyt ox activity after 7 days of collapse (P < 0.05), whereas cyt ox activity in contralateral left lungs did not change. Pyruvate kinase activity, a marker for anaerobic glycolysis resulting from tissue hypoxia, increased 49% in collapsed right lungs (P < 0.01). Cyanide-insensitive respiration was 83% higher in 7 day-collapsed lungs (2.28 ± 0.66 μl O2 · min-1 · g-1) compared with contralateral lungs (1.24 ± 0.34, P < 0.05), indicating increased superoxide and H2O2 production in this tissue after homogenization at normoxic PO2 (~150 Torr). These data indicate that collapsed lung tissue has decreased mitochondrial SOD and cytochrome oxidase, changes that could enhance O2 free radical production during the reoxygenation that accompanies reexpansion.
ASJC Scopus subject areas
- Physiology (medical)