Collagen mRNA content and distribution in the lungs of rats exposed to ozone

cDNAs, synthesized by the polymerase chain reaction (PCR) technique, were used to quantify mRNA concentrations for the alpha 1 (I) and alpha 1 (III) chains of collagen types I and III and for beta-actin in the lungs of rats exposed to either filtered air or to 1.2 ppm of ozone. The alpha 1 (I) procollagen mRNA concentration was increased by about 30% in the lungs of rats exposed to ozone, while the concentrations of the mRNAs for alpha 1 (III) procollagen and for beta-actin were the same in the lungs of control and ozone-exposed animals. The lungs from the rats exposed to 1.2 ppm of ozone preferentially synthesized type I collagen as compared with controls. Sites of increased expression of the alpha 1 (I) procollagen mRNA were detected by in situ hybridization in lung sections embedded in paraffin prepared from rats exposed either to filtered air or to ozone. The lungs from rats treated with ozone focally expressed increased amounts of alpha 1 (I) procollagen mRNA in the lung parenchyma at the septal tips and the bronchiole-alveolar duct junctions. They also showed an apparent diffuse increase in alpha 1 (III) procollagen mRNA expression. We conclude that exposure of rats to high concentrations of ozone causes a specific increase in the lung content of mRNA for the major chain of type I collagen.