PLATELET-DERIVED GROWTH-FACTOR AND GROWTH-RELATED GENES IN RAT LUNG .2. EFFECT OF EXPOSURE TO 85-PERCENT O2

The expression of platelet-derived growth factor (PDGF), its receptor, and related genes was studied in the lung tissue of rats exposed to air or 85% O2. PDGF-B chain mRNA was increased by 6 days and PDGF B-type receptor mRNA was increased by 4 and 6 days of exposure to 85% O2. Despite a continued increase of cell division, both PDGF-B chain and B-type receptor mRNAs had returned to control values by 14 days of exposure to 85% O2. PDGF-A chain mRNA was unaffected by exposure to 85% O2. Nuclear runoff transcription analysis confirmed increased transcription of PDGF-B chain mRNA, whereas Western blot analysis of lung homogenates suggested consequent increased translation of PDGF-B chain mRNA to PDGF-BB at 7 days of exposure to 85% O2. Combined immunocytochemistry and autoradiography localized PDGF-BB to the major site of cell division, the pulmonary interstitium. We speculate that the early pulmonary fibroblast hyperplasia observed following exposure to 85% O2 is mediated by increased PDGF-B chain gene expression and may also be mediated by changes in PDGF B-type receptor gene expression.