Objective: To study the effect of polydatin on p hospholipase A_2 in lung tissues in rats with endotoxic shock. Methods: Thirty-two healthy male Wistar rats were employed in this study. A total of 8 rats received normal saline intravenously (control grou p),8 rats received 10 mg/kg of endotoxin (endotoxic shock group),8 rats re ceived 1 mg/kg of polydatin after endotoxin injection (polydatin treatment g roup),and 8 rats received 1 mg/kg of polydatin (polydatin prevention group) 30 minutes before endotoxin injection. Mean arterial pressure was measured once hal f an hour. Lung tissues were collected 6 hours later. Phospholipase A_2 activit y was measured with acid titration. The gene expression of secretory phospholipa se A_2 type IIA was detected with reverse transcription polymerase chain reacti on. Meanwhile,the histological changes of the lungs among four groups were comp ared through microscopic examination.Results: Phospholipase A_2 activity and the gene expression of secretory phospholipase A_2 type IIA increased after endotoxin injection,but polydatin could inhibit these effects of endotoxin. Obvious morphological eviden ce could be found in the lung pathological sections and the protective effect of polydatin was most significant in the polydatin prevention group.Conclusions: Polydatin has prophylactic and therapeutic effects (the former is more distinct than the latter) on acutely injured lungs in rats with endotoxic shock and which suggests that polydatin may be a phospholipase A _2 inhibitor. Objective: To study the effect of polydatin on p hospholipase A_2 in lung tissues in rats with endotoxic shock. Methods: Thirty-two healthy male Wistar rats were employed in this study. A total of 8 rats received normal saline intravenously (control grou p) , 8 rats received 10 mg / kg of endotoxin (endotoxic shock group), 8 rats re ceived 1 mg / kg of polydatin after endotoxin injection (polydatin treatment g roup), and 8 rats received 1 mg / kg of polydatin prevention group The tissues were collected 6 hours later. Phospholipase A_2 activit y was measured with acid titration. The gene expression of secretory phospholipa se A_2 type IIA was detected with reverse transcription polymerase chain reacti on. the histological changes of the lungs among four groups were comp ared through microscopic examination. Results: Phospholipase A_2 activity and the gene expression of secr etory phospholipase A_2 type IIA increased after endotoxin injection, but polydatin could inhibit these effects of endotoxin. Obvious morphological eviden ce could be found in the lung pathological sections and the protective effect of polydatin was most significant in the polydatin prevention group. Conclusions: Polydatin has prophylactic and therapeutic effects (the former is more distinct than the latter) on acutely injured lungs in rats with endotoxic shock and which suggests that polydatin may be a phospholipase A _2 inhibitor.