It has been reported that the g1ycoprotein extracted from A10e has strong anti-inflammatory response， However， there has been no research report yet about the effect of A10e on allergic hypersensitivity reactivity， By using guinea pig 1ung mast cells， this study aimed to examine the effects of A10e g1ycoprotein (NY945) on the mediator re1eases caused by mast cell activation， and a1so aimed to assess the effects of NY945 on the mechanism of mediator re1eases in the mast cell activation. We partially purified mast cell from guinea pig 1ung tissues by using the enzyme digestion， the rough and the discontinuous density percoll gradient method. Mast cells were sensitized with IgG1 (anti-OA) and challenged with ova1bumin. Histamine was assayed by fluorometric ana1yzer， 1eukotrienes by radioimmunoassay. The phospholipase D activity was assessed by the production of 1abe1ed phosphatidy1alcoho1. The amount of mass 1， 2-diacy1g1ycero1 (DAG) was measured by the eH]DAG produced when pre1abe1ed with eH]myristic acid. The phosph01ipid methy1ation was assessed by measuring the incorporation of the eH]methy1 moiety into phosph01ipids of cellu1ar membranes. Pretreatment of NY945 (10 μg) significant1y decreased histamine and 1eukotrienes re1eases during mast cell activation. The decrease of histamine re1ease was stronger than that of 1eukotriene during mast cell activation. The phospholipase D activity increased by the mast cell activation was decreased by the dose-dependent manner in the pretreatment of NY945. The amount of DAG produced by PLC activity was decreased by NY945 pretreatment. The amount of mass 1， 2-diacy1g1ycero1 produced by activation of mast cells was decreased in the pretreatment of NY945. NY945 pretreatment strong1y inhibited the incorporation of the eH]methy1 moiety into phosph01ipids. The data suggest that NY945 purified from A10e inhibi엄 in part an increase of 1， 2-diacy1g1ycero1 which is produced by activating mast cells with antigen-antibody reactions， which is mediated via phosphatidylcholinephospholipase D and phosphatidylinosit01-phospholipase C systems， and then followed by the inhibition of histamine re1ease. Furthermore， NY945 reduces the production of phosphatidylch01ine by inhibiting the methy1transferase 1 and II， which decreases the conversion of phosphatidylcho1ine into arachidonic acid and inhibits the production of 1eukotrienes.