Exogenous surfactant instillation attenuates inflammatory response to acid-induced lung injury in rat

The present study was performed to investigate the role of exogenous surfactant on hydrochloric acid (HCL) - induced lung injury in rats. Six-week-old male Sprague-Dawley rats were anesthetized by intraperitoneal injection of pentobarbital sodium (40 mg/kg) and HCL (0.1 N, 2 mL/kg) or normal saline (NS, 2 mL/kg) was instilled into the trachea. Thirty minutes after HCL instillation, surfactant at a dose of 60 mg (=2 mL)/body or NS (2 mL) was instilled into the rat lungs. Animals in another experimental group were also treated with the same dose of surfactant supplement 2 hours after the first administration. Bronchoalveolar lavage fluid (BALF) was obtained 5 hours after HCL instillation. In BALF, increases in total nuclear cell counts, neutrophil counts, optical density at 412 nm as an indicator of pulmonary hemorrhage, neutrophil elastase activity, concentrations of albumin and cytokine-induced neutrophil chemoattractant (CINC) induced by HCL instillation were significantly attenuated by surfactant treatment. The wet-to-dry weight (W/D) ratio in the lung and partial oxygen tension (PO2) were also estimated; surfactant treatment significantly attenuated the W/D ratio and improved deteriorated PO2 induced by HCL. Additional surfactant supplementation did not show further beneficial effects on HCL-induced lung injury compared with a single treatment. These results suggest that surfactant shows an anti-inflammatory effect on acid lung injury in rats but the beneficial effects may be dose limited.