The Role And Mechanism Of XQ As Deriver Of Gingkolide B On Inhibiting Platelet Aggregation

Infuence of XQ administrated in vitro on PAF, ADP, AA and COL-inducedplatelet aggregation in rabbit ex vivoObjective To investigate the bio-activity of influence of XQ on platelet aggregation,platelet adhesion, and the release function of PAF-induced platelet for providing referencein the clinical treatment of XQ.Method With Troxerutin, Dipyridamole and Gingkolide B （GB） as control drugs, （1）Withurbidity method, to assay the effect of XQ, administrated at different final concentration invitro, via i.v. one time, or via i.v. more times, on inhibiting PAF, ADP, AA andCOL-induced platelet aggregation in rabbit.（2） With platelet count, to assay the effect ofXQ, administrated via i.v. for 5 days, on COL-induced platelet adhesion in rabbits. （3） Withfluorospectrophotometry, to assay the effect of XQ, administrated at different finalconcentration in vitro or via i.v. for 5 days, on the release of 5-HT from PAF-inducedplatelet in rabbits. （4） According to the principle of the bio-transformation that TXA₂ andPGI₂ can rapidly transform TXB₂ and 6-keto-PGF_1αthrough bio- transformation system,respectively. With radio-immunity;radioimmunity, to assay the effect of XQ, administratedvia i.v. for 5 days, on the release of TXA₂ and PGI₂ from PAF-induced platelet in rabbits. （5）With fluorospectrophotometry, to assay the effect of XQ, administrated in vitro or via i.v.for 5 days, on the release of [Ca²⁺] from PAF-induced platelet in rabbits. （6） With ELISA,to assay the effect of XQ, administrated via i.v. for 5 days, on the release ofβ-TG and PF4from PAF-induced platelet in rabbits. （7） With the method of radiation ligand, to assay thecapability of antagonism of XQ to the binding of PAF to PAF receptors of rabbit platelet.Result（1） XQ, at 0.037, 0.37, 3.7, 37, 370, 1852, 3704μg/ml, have the effect on inhibition on PAF,ADP, AA and COL-induced platelet aggregation in rabbit. Among them, 370μg/ml XQ and370, 3704μg/ml XQ statistically have the significant effect on inhibiting PAF andADP-induced platelet aggregation in rabbit, P＜0.01, respectively. IC50 of XQ arerespectively 0.149μg/ml, 720μg/ml, 178μg/ml, 4693μg/ml for inhibiting PAF, ADP, AA and COL-induced platelet aggregation in rabbit. Three groups （administrated 0.25, 0.5,1mg/kg XQ for one day） have the weaker effect on inhibiting PAF, ADP, AA andCOL-induced platelet aggregation in rabbit, and it statistically isn’t significant, comparedwith normal group. Three groups （administrated 0.25, 0.5, 1mg/kg XQ for three days） havethe weaker effect on inhibiting PAF, ADP, AA and COL-induced platelet aggregation inrabbits. Among them, 0.25, 0.5, 1mg/kg XQ, 0.5, 1 mg/kg XQ and 0.5 mg/kg XQstatistically have the significant effect on inhibiting PAF, ADP and AA and COL-inducedplatelet aggregation in rabbit, P＜0.05, 0.01, respectively, compared to normal group.（2） Three groups （0.25, 0.5, 1 mg/kg XQ） statistically have the significant effect oninhibiting COL-induced platelet adhesion in rabbits, compared to normal group, P＜0.05,0.01.（3） XQ, at 0.037, 0.37, 3.7, 37, 370, 3700μg/ml, statistically have the significant effect onthe release of 5-HT from PAF-induced platelet in rabbits, （P＜0.05, P＜0.01）, compared tonormal group. Three groups, 0.25, 0.5, 1mg/kg XQ, have the effect on the release of 5-HTfrom PAF-induced platelet in rabbits. Among them, two groups, 0.5, 1mg/kg XQ,statistically have the significant effect on the release of 5-HT from PAF-induced platelet inrabbits, （P＜0.01）, compared to normal group.（4） Three groups, 0.25, 0.5, 1mg/kg XQ, have the effect on inhibiting the release of TXA₂and PGI₂ from PAF-induced platelet in rabbits, and decreasing TXB₂/6-keto-PGF_1α value.Among them, XQ, at 1mg/kg, statistically have the significant effect on the release of 5-HTfrom PAF-induced platelet in rabbits, （P＜0.05）, compared to normal group.（5） Six groups, 0.036, 0.36, 3.6, 36,360, 3600μg/ml XQ, statistically have the significanteffect on inhibiting the release of Ca²⁺ from PAF-induced platelet in rabbits, （P＜0.01）,compared to normal group. Three groups, 0.25, 0.5, 1mg/kg XQ, have the effect on therelease of [Ca²⁺] from PAF-induced platelet in rabbits. Among them, two groups, 0.5,1mg/kg XQ, statistically have the significant effect on the release of [Ca²⁺] fromPAF-induced platelet in rabbits, （P＜0.01）, compared to normal group.（6） Three groups （0.25, 0.5, 1 mg/kg XQ） statistically have the significant effect on therelease ofβ-TG and PF4 from PAF-induced platelet in rabbits, compared to normal group,P＜0.05, 0.01.（7） The equilibrium dissociation constant（KD） and maximum binding capacity of [³H]PAF are 1.65×10^-2 nmol/L and 7.99×10^-12nmol/10⁸ platelets, respectively. K_i of XQ and GB are 9.6210×10^-3 and 7.21×10^-2nmol/L, respectively. Conlusion For XQ can competitively previously bind the PAF receptors of rabbit platelet inthe present of PAF, XQ can have the effect of inhibition on PAF, ADP, AA andCOL-induced platelet aggregation, inhibit the function of platelet adhesion, and inhibit therelease ftmction of rabbit platelet, sucn as release of 5-TH, Ca²⁺, TXA₂,β-TG; PF4 and soon. Meanwhile, affinity of XQ to PAF receptors is higher than that of GB.