Retinoic acid enhances lung growth after pneumonectomy

Background. We sought to identify the role of retinoic acid (RA) upon lung growth. RA has a role in perinatal lung development, and we hypothesized th at exogenous RA would enhance postpneumonectomy compensatory lung growth. Methods. Utilizing the postpneumonectomy rat model, we studied the impact o f RA upon contralateral lung growth. Adult Sprague-Dawley rats were divided into three groups. Group S underwent a sham left thoracotomy, group P unde rwent left pneumonectomy, and group R underwent left pneumonectomy with adm inistration of exogenous RA (0.5 mug/g/day intraperitoneally). We then quan titated right lung growth after 10 and 21 days. Lung weight and volume were expressed as a ratio to the final body weight (lung weight and volume indi ces, LWI and LVI). Epidermal growth factor receptor (EGFR) expression was q uantitated using Western blot analysis. Cellular proliferation index (CPI) was determined using BrdU immunostaining. Results. LWI, LVI, CPI, and EGFR expression at 21 days were significantly h igher in group R versus S and P. At the 10-day interval, both LWI and LVI w ere significantly higher in group R versus S and P. Conclusions, RA administration markedly enhances lung growth after pneumone ctomy, as evidenced by increases in LWI, LVI, and CPI. Upregulation of EGFR expression was associated with these effects. (Ann Thorac Surg 2001 71:164 5-50) (C) 2001 by The Society of Thoracic Surgeons.