Actavia 0 Li, Jun-Liang Xu, Yuan-Qing Shi, Bin-Lin Sun, Deng-Sheng Yan, Su-Mei Guo, Xiao-Yu 2017 2017-2-28 58-66 The effects of chitosan on immune function via arachidonic acid (AA) pathway in weaned piglets were investigated. A total of 180 piglets (Duroc × Yorkshire × Landrace) were randomly assigned to 5 dietary treatments and fed a basal diet supplemented with 0 (control), 100, 500, 1000, and 2000 mg chitosan/kg feed, respectively. Results showed that serum AA, prostaglandin E2 (PGE2), and leukotriene B4 (LTB4) contents in piglets were increased in a linear or quadratic dose-dependent manner with increasing chitosan on day 28 (P < 0.05). Chitosan increased serum cytosolic-phospholipase A2 (cPLA2) activity in a linear or quadratic dose-dependent manner on day 14 or 28, and improved 5-lipoxygenase (5-LOX) activity in a linear manner and cyclooxygenase-2 (COX-2) activity quadratically on day 28 (P < 0.05). Moreover, chitosan elevated gene expression of cPLA2 mRNA quadratically in the small intestine on days 14 and 28, increased the COX-2 mRNA expression in the duodenum or jejunum in a linear or quadratic manner on day 28, and improved the 5-LOX mRNA expression quadratically in the small intestine (P < 0.05). These results implied that the metabolism of AA was regulated by chitosan in a dose-dependent relationship, which may be one reason why chitosan affected immune function via AA pathway in weaned piglets. 2 62