Effect of chronic exposure to nitrogen dioxide on collagen content in lung and skin of guinea pigs

The influence of nitrogen dioxide on the connective tissue of guinea pigs was studied after 180 days (8 hours per day) of exposure at a concentration of 2 mg/m³. The long-term exposure induced a decrease of total collagen content in lung tissue, and an increase in skin as well as an increase of collagen catabolite levels in blood serum and urine. The increase of soluble fractions of collagen and the decrease of insoluble ones was found in skin of the exposed animals. Morphological studies showed nitrogen dioxide-induced emphysema and damage in bronchioli of the lungs and some degenerative skin changes. The results obtained suggest the inhibition of collagen maturation and/or activation of its catabolism as the main mechanism of nitrogen dioxide-induced connective tissue damage.