Effects of oxygen toxicity on cuprolinic blue-stained proteoglycans in alveolar basement membranes

Effects of oxygen toxicity on distribution and density of proteoglycans in basement membranes of newborn rat lungs were assessed by electron microscopic analysis of tissues processed with cuprolinic blue, a cationic label that characteristically labels these anionically charged macromolecules. Newborn rats placed in greater than 95% oxygen at birth were killed at weekly intervals for 4 wk, and lung tissues fixed in 2.5% glutaraldehyde with 0.2% cuprolinic blue were processed for electron microscopy. Alveolar basement membranes from oxygen-treated and control animals were compared for differences in thickness and proteoglycan concentration and distribution. Results showed progressive thickening of alveolar basement membranes with increased duration of oxygen exposure. The normal distribution of proteoglycans, which is predominantly in the lamina rara externa of alveolar basement membranes, was frequently lost in thickened membranes found in oxygen-treated animals. Density of proteoglycans in these membranes decreased to 56% of normal by 2 wk of age and remained low with continued oxygen administration. Proteoglycan concentration in basement membranes on the interstitial side of alveolar capillaries in both control and oxygen-treated animals was low compared with proteoglycan concentration in basement membranes that opposed the alveolar air space, and administration of oxygen diminished these differences. These results demonstrate a direct alteration of proteoglycan distribution and density in the developing lung as a result of oxygen toxicity. This could result in decreased cell adhesion, influence the cellular response to lung injury, and contribute to the increased permeability seen with this disorder.