The Corrected Collagen Content in Paraquat Lungs

Biochemical analysis of collagen in a fibrosing lung often betrays its collagen-rich appearance in histopathology. This is due to the liability of lung tissue to extreme change in weight or volume in the presence of edema, hemorrhage, or other lesions, producing a great error in the biochemical data obtained from it. On morphometry of arterial density in lung section, we established a method for calculating the degree to which a given lung is transformed from a standard state of expansion, according to which we may correct for the content of collagen per lung volume. This method was applied to 14 autopsy paraquat lungs with various grades of fibrosis. Increase in collagen was shown to begin at about the 20th day of intoxication and advance thereafter, a finding in good accordance with lung morphology. The longer the survival, the less uniform the intrapulmonary distribution of collagen; even a severely fibrosing lung retained nonfibrotic areas.