The presence of collagen in lung is fundamental in normal structure and function. Methods were developed to examine human fetal and adult lung collagen with respect to its composition and synthesis. The second trimester fetal lung has a large number of cells per unit lung mass (36.6±2.7 μg DNA/mg dry wt), and relatively small amounts of collagen (17.0±5.3 μg collagen/mg dry wt). The number of cells per unit lung mass in the adult lung (11.1±3.4 μg DNA/mg dry wt) is 30% of the number of cells in the fetal lung, but the adult has 11 times more collagen (196±25 μg collagen/mg dry wt). The composition of fetal lung collagen can be partially characterized by extraction with salt at neutral pH, acetic acid, or guanidine. The extracted chains, representing 10% of the total lung collagen, chromatograph as α1 and α2 chains, each with a mol wt of 100,000 and an amino acid composition characteristic for collagen but not specific for lung. Short term explant cultures of fetal and adult lung synthesize α chains which can be isolated by ion exchange chromatography. These chains, representing 30 to 40% of the total collagen synthesized by the explants, coelectrophorese with extracted collagen chains on acrylamide gels; they are destroyed by clostridial collagenase and they have a mol wt of 100,000. Although the composition of the collagen synthesized by these explants can be only partially characterized, the rate of synthesis of both collagen and noncollagen protein can be quantified. In fetal lung, 4.0±1.2% of the amino acids incorporated into protein per hr are incorporated into collagen. In normal adult lung, this percentage (4.2±0.9%) is remarkably similar. These values are almost identical to the relative rate of collagen synthesis in rabbit lung in the same age range. This technology should be applicable to answer specific questions regarding collagen synthesis and degradation in human lung disease.
ASJC Scopus subject areas