Age-related fluorescence in rat lung collagen.

Mechanical lung properties are impaired with age. In other organs an age-related increase in collagen-linked fluorescence, attributable to advanced glycation endproducts (AGE), or other nonenzymatic reactions such as those related to lipid peroxidation derivatives has been described. Moreover, oxidative processes accelerate some of these reactions. In several tissues, these AGE products have been found to be responsible for protein cross-linking and lack of elasticity. We have evaluated the fluorescence levels of lung collagen in rats aged from 1 to 25 months at two distinct wavelengths: the standard AGE fluorescence (Exc 370 nm/Em 440 nm) and the pentosidine fluorescence (Exc 335 nm/Em 395 nm). In pulmonary tissue fluorescence at both 370/440 nm (p < 0.05) and 335/395 nm (p < 0.001) increases with age. However, a relative stabilization of values is seen in the 25 months group that could be related to the kinetics of fluorescent products in vivo. So, as observed in other tissues, AGE products may increase in pulmonary tissues with time. This may explain the age-associated decline in pulmonary compliance.