Collagen concentration and rates of synthesis in idiopathic pulmonary fibrosis.

To define the biochemical correlates of the apparent morphologic increase in lung interstitial collagen in idiopathic pulmonary fibrosis (IPF), collagen content was quantitated, and the morphologic degree of fibrosis was assessed in 9 patients with IPF and 6 control subjects. There were no significant differences in the collagen content among patients with IPF compared with that of control subjects. In addition, there was no correlation between collagen content and the morphologic assessment of the degree of fibrosis. Analysis of the collagen content from multiple sites made from base to apex of postmortem material from 3 patients with IPF and 2 control subjects demonstrated a wide, but similar, variation in collagen content in both groups; no definite pattern of anatomic distribution was found in either the patients with IPF or the control subjects. Furthermore, the rates of collagen and noncollagen protein synthesis in explants of lung of patients with IPF demonstrated no significant differences compared with those of the control subjects. The results of this study are consistent with the concept that IPF is a disease of an alteration in quality, form, and location of collagen rather than simply a disease of increased interstitial collagen.