139EFFECT OF RETINOIC ACID ON ARTERIAL BLOOD GASES, PROTEIN AND DNA CONTENT IN RAT LUNG FOLLOWING UNILATERAL PNEUMONECTOMYPatients who undergo complete or partial pneumonectomy suffer from insufficient oxygenation leading to reduced quality of life. Retinoic acid being an important signaling molecule during normal lung development could enhance the lung function following pneumonectomy. The aim of the study was to evaluate the effect of retinoic acid on arterial blood gases, protein content and DNA content in rats following unilateral pneumonectomy. Unilateral pneumonectomy of left lung was performed in male wistar albino rats. Retinoic acid (0.5 mg/kg) or vehicle was administered intraperitoneally for 10 days. Lung weight, lung volume, arterial blood gas analysis, protein and DNA estimations were performed on the contralateral lung to assess the effect of retinoic acid. Weight and volume of the compensatory lung were increased in rats treated with retinoic acid to compensate for the loss of the unilateral lung compared to control. Protein concentration and DNA concentration were also increased in the contralateral lung in rats treated with retinoic acid compared to control. In arterial blood gas analysis (ABG) rats treated with retinoic acid shows an increased partial pressure of oxygen but there was no significant change in partial pressure of carbondioxide and oxygen saturation percentage in retinoic acid treated rats. Retinoic acid accelerates compensatory lung growth in rats possibly by increasing proliferation of type II pneumocytes in lung which is shown by increase in protein and DNA concentration. However its effect on oxygenation of blood is not significantly increased, may be due to short duration of treatment. Increasing the duration of treatment may improve oxygenation and quality of life. Retinoic acid can be useful especially in patients undergoing lung volume reduction surgery with low respiratory reserve. drsarvan.ssss@gmail.comResearch612016Retinoic acid,Pneumonectomy,Compensatory growthR Saravanan,S RajaramPh.D scholar, Department of Pharmacology, Vinayaka Missions University, Salem, Tamilnadu, India.,Professor, Department of Pharmacology, Vinayaka Missions Kirupananda Variyar Medical College and Hospital, Salem, Tamilnadu, India.