Age-associated changes in elastin and collagen content and the proportion of types I and III collagen in the lungs of mice.

We investigated the effect of aging on the extracellular matrix of the lungs by examining age-associated changes in the elastin and collagen content, and the proportion of types I and III collagen, in the whole lungs of BALB/c and SAMR1 male mice between the ages of 3 and 24 months. The elastin content was determined by the hot alkali method. The hydroxyproline content was measured and assessed to be the collagen content. The relative proportion of types I and III collagen was assessed by cyanogen bromide digestion, followed by separation of the resultant peptides by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The elastin content did not change significantly with age in either strain of mice. The total collagen content of the whole lung was significantly higher at 24 months of age, although there were no significant changes with aging in the hydroxyproline content per dry lung weight nor in the proportion of type III to type I collagen. We conclude that in terms of the extracellular matrix, the lungs of aged mice are not very different in feature from the lungs of younger mice, and this is probably the simple consequence of growth of the lungs of young mice.