QUANTITATIVE IMMUNOCYTOCHEMICAL ANALYSIS OF MN SOD IN ALVEOLAR TYPE-II CELLS OF THE HYPEROXIC RAT

We have analyzed the magnitude and uniformity of the expression of man ganese superoxide dismutase (Mn SOD) protein in alveolar type II cells of rats exposed to hyperoxia using quantitative colloidal gold immuno cytochemistry and morphometric techniques. Sprague-Dawley rats were ex posed continuously to normal air or to 85% oxygen for 7 and 14 days. T he lungs were fixed by intratracheal instillation of a paraformaldehyd e-glutaraldehyde fixative. Lung samples were dehydrated in ethanol and embedded in LR-White. Thin sections for electron microscopy were labe led with anti-rat Mn SOD rabbit antiserum followed by protein-A gold. The labeling density (gold particles/mu m(2)) over subcellular compart ments was determined, and relative organelle volumes were measured usi ng a random point overlay. The results confirm that alveolar type II c ells are a locus of Mn SOD response in the lungs of hyperoxic rats and contribute to this response through a combination of changes: an incr ease of Mn SOD concentration in the mitochondrial matrix, an increase of mitochondrial volume per cell, and type II cell hyperplasia.