LUNG CAPILLARY ALBUMIN LEAK IN OXYGEN-TOXICITY A QUANTITATIVE IMMUNOCYTOCHEMICAL STUDY

The study is based on the hypothesis that lung endothelial cell permea bility increases in 100% oxygen and predates the appearance of microsc opically visible interstitial edema. Rats were exposed to either 100% oxygen or air in a chamber: Endogenous albumin was used as an index of permeability and measured by electron microscopic colloidal gold link ed immunocytochemistry, quantified by systematic random methods. Album in staining was expressed as relative albumin concentration (RAC), the ratio of gold particles (x100) per point counted (gp.10(2)/pt) relati ng to each component. The RAC in lung perivascular/peribronchial inter stitial ground substance after 24 h of hyperoxia was five times more t han that of rats exposed to air for the same interval. The median valu e (interquartile ranges) for the oxygen-exposed group was 92.4 (39.5, 149.6) gp.10(2)/pt compared with 14.7 (6.6, 25.9) gp.10(2)/pt for the air-exposed group. After 60 h of 100% oxygen, the RAC was 103.4(65.5, 148.9) gp.10(2)/pt (60-h air exposed RAC was 11.6(8.7, 60.4) gp.10(2)/ pt), no different from 24-h exposures. These results suggest that ther e was a significant leak of albumin to the perivascular/peribronchial interstitium by 24 h of exposure to 100% oxygen, which would indicate endothelial cell permeability to albumin increases earlier than has pr eviously been reported.