Background and aim: The study investigates the immune response of the lung alveolar macrophages in adult rats with intratracheal instillation of surfactant, isolated from porcine, rabbit and rat lung as well as the synthetic surfactant.

Material and methods: Adult male rats were divided into five groups: Controls were instilled with buffer, similarly P-SF, R-SF, r-SF, and S-SF group of animals were instilled with porcine, rabbit, rat and synthetic surfactant, respectively.

Results: After one month, IL-1β secretions were found to be elevated in the supernatant of alveolar macrophages. Further, nitric oxide (NO) level was elevated with porcine and synthetic surfactant, while reactive oxygen species (ROS) generation was found to be inhibited significantly in all the treatment groups. Apoptoses were studied by using fluorescence dyes acridine orange/ethidium bromide, where percent of the apoptotic cells were found to be decreased in all the treated groups.

Conclusions: Exogenous surfactant elevates secretion of pro-inflammatory cytokine IL-1β and also the NO as signaling molecule. The inhibitory effects of surfactants on ROS generation and on apoptosis may result from the interruption in the cell signaling pathway. In the treatment of respiratory distress syndrome, the anti-inflammatory response of surfactant may thus depend upon the specific preparation of the surfactant.