Increased Elastin and Collagen Content in the Lungs of Hamsters Receiving an Intratracheal Injection of Bleomycin1,2

Bleomycin was administered by intratracheal injection to hamsters. Thirty days after a single injection of 1 unit, the lungs showed patchy fibrosis that involved air spaces, terminal bronchioles, and pleura. Connective tissue stains indicated increased amounts of collagen and elastin in the fibrotic areas. Biochemical analysis of the lungs revealed that the amounts of both collagen and elastin were increased more than 2-fold above control values. The number of desmosine cross links per elastin molecule was the same in the control lungs and the lungs treated with bleomycin. Bleomycin concentrations of 2 units or more resulted in high mortality rates. This experimental model of pulmonary fibrosis is useful for studying metabolic control of the connective tissues in the lung.