OBJECTIVETo explore the inhibitory effect and mechanism of rutin against platelet activating factor (PAF) induced platelet aggregation, 5-HT release and intra-platelet free calcium concentration.

METHODSThe rate of washed rabbit platelet (WRP) aggregation was measured by turbidimetry and O-phthaldialdehyde (OPT) fluoro-spectrophotometry (FSPM) was used to determine 5-HT content. The intraplatelet free calcium concentration was measured with Fura-2/AM FSPM assay.

RESULTSRutin in vitro was concentration-dependently inhibiting PAF (9.55 x 10(-9) mol/L) induced WRP aggregation, the IC50 of 5-HT release was 0.73, 1.13 mmol/L respectively and the intraplatelet free calcium concentration elevation evoked by PAF (4.78 x 10(-10) mol/L) were inhibited by 68.3, 136, 274, 545 mumol/L of rutin dose-dependently.

CONCLUSIONRutin could inhibit PAF induced platelet aggregation, 5-HT release and the increase of intraplatelet free calcium.

Animals ; Biological Transport, Active ; Blood Platelets ; metabolism ; Calcium ; metabolism ; Male ; Platelet Activating Factor ; antagonists & inhibitors ; Platelet Activation ; drug effects ; Platelet Aggregation Inhibitors ; pharmacology ; Rabbits ; Rutin ; pharmacology ; Serotonin ; metabolism

AIMTo observe the levels of interleukin-12 (IL-12) and platelet activating factor (PAF) in severe acute pancreatitis (SAP) in rats and the efficacy of Ginkgolide B (BN52021) in treating SAP.

METHODSWistar rats were randomly divided into 3 groups: model group (SAP), treatment group (BN) and negative control group (NC). SAP was induced by retrograde infusion of 5% sodium taurocholate into the pancreatic duct in Wistar rats. NC rats only receive abdominal incision. In groups of SAP and NC rats received the femoral vein injection of isotonic Na chloride 15 minutes after induction of SAP; in BN group,rats received BN52021 instead. After operation rats were sacrificed at 1, 6 and 12 hour for plasma IL-12 and PAF determined with ELISA.

RESULTSAn increase of IL-12 in group BN was observed VS group SAP or group NC at 1 h stage (p = 0.011, P < 0.01). At 6 h or 12 h stage,an increase of IL-12 in group SAP was observed VS group NC (P < 0.01, P < 0.05). The plasma level of PAF in group SAP or group BN was increased significantly at 1 h time stage VS group NC (P < 0.001). At 6 h or 12 h stage, a decrease of PAF in group BN or group NC was observed VS group SAP (P < 0.05, P < 0.01).

CONCLUSIONIt confirmed that the plasma level of cytokine IL-12 in SAP group was decreased significantly in early stage and it witnessed a remarkable increase of cytokine PAF. The plasma level of IL-12 was increased in early stage but PAF was decreased in rats treatment by BN52021 which inhibited the development of SAP.

Acute Disease ; Animals ; Ginkgolides ; pharmacology ; Interleukin-12 ; blood ; Lactones ; pharmacology ; Male ; Pancreatitis ; blood ; Platelet Activating Factor ; metabolism ; Rats ; Rats, Wistar

Animals ; Cells, Cultured ; Female ; Granulosa Cells ; metabolism ; Pituitary Adenylate Cyclase-Activating Polypeptide ; genetics ; metabolism ; Platelet Activating Factor ; pharmacology ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley

AIMTo study the antagonistic effect of myricetin on platelet activing factor (PAF).

METHODSThe specific binding of [3H] PAF to rabbit platelet receptor was investigated using radio ligand binding assay (RLBA). Platelet adhesion induced by PAF was measured with spectrophotometry. The elevation of inner free calcium concentration in rabbit polymorphonuclear leukocytes (PMNs) induced by PAF was assayed by Fura-2 fluorescent technique.

RESULTSThe specific binding inhibition potency of Myr was found to be concentration-dependent. The IC50 of Myr in [3H] PAF 1, 2 and 4 nmol.L-1 were 34.8, 85.7 and 118.6 mumol.L-1, respectively. The PAF induced reactions of rabbit platelet adhesion and PMNs inner free calcium concentration increase were inhibited by Myr in a dose-dependent manner. The IC50 of Myr to inhibit platelet adhesion was 13.1 mumol.L-1.

CONCLUSIONThe specific receptor binding of PAF can be antagonized by myricetin.

Animals ; Calcium ; metabolism ; Flavonoids ; pharmacology ; Male ; Neutrophils ; metabolism ; Platelet Activating Factor ; antagonists & inhibitors ; metabolism ; Platelet Activation ; drug effects ; Platelet Adhesiveness ; drug effects ; Platelet Aggregation Inhibitors ; pharmacology ; Platelet Membrane Glycoproteins ; metabolism ; Rabbits ; Receptors, G-Protein-Coupled ; metabolism

OBJECTIVETo observe the platelet activating factor (PAF) antagonistic effect of kaempferol.

METHODThe specific binding of [3H] PAF to rabbit platelet receptor was investigatedwith radio ligand binding assay (RLBA). Platelet adhesion induced by PAF was measured with spectrophotometry. The elevation of inner free calcium concentration in rabbit polymorphonuclear leukocytes (PMNs) induced by PAF was determined with Fura-2 fluorescent technique.

RESULTThe 1, 2 or 4 nmol x L(-1) [3H]PAF specific binding to rabbit platelet receptor was inhibited by Kae dosage dependently and the IC50 were 30.8, 74.6 and 92.0 micro mol x L(-1), respectively. The PAF induced reactions of rabbit platelet adhesion and PMNs inner free calcium concentration elevation were inhibited by Kae in a dose-dependent manner. The IC50 of Kae to inhibit platelet adhesion was 65 micromol x L(-1).

CONCLUSIONKae is effective in inhibiting the action of PAF and it is a new PAF receptor antagonist.

Animals ; Blood Platelets ; drug effects ; physiology ; Calcium ; metabolism ; Kaempferols ; pharmacology ; Male ; Neutrophils ; metabolism ; Platelet Activating Factor ; metabolism ; Platelet Adhesiveness ; drug effects ; Platelet Membrane Glycoproteins ; antagonists & inhibitors ; metabolism ; Rabbits ; Radioligand Assay ; Receptors, G-Protein-Coupled ; antagonists & inhibitors ; metabolism

The present study was carried out to examine the mechanisms of the synergistic interaction of PAF and A23187 mediated platelet aggregation. We found that platelet aggregation mediated by subthreshold concentrations of PAF (5 nM) and A23187 (1 micrometer) was inhibited by PAF receptor blocker (WEB 2086, IC50=0.65 micrometer) and calcium channel blockers, diltiazem (IC50=13 micrometer) and verapamil (IC50=18 micrometer). Pretreatment of platelets with PAF and A23187 induced rise in intracellular calcium and this effect was also blocked by verapamil. While examining the role of the down stream signaling pathways, we found that platelet aggregation induced by the co-addition of PAF and A23187 was also inhibited by low concentrations of phospholipase C (PLC) inhibitor (U73122; IC50 = 10 micrometer), a cyclooxygenase inhibitor (indomethacin; IC50=0.2 micrometer) and inhibitor of TLCK, herbimycin A with IC50 value of 5 micrometer. The effect was also inhibited by a specific TXA2 receptor antagonist, SQ 29548 with very low IC50 value of 0.05 micrometer. However, the inhibitors of MAP kinase, PD98059 and protein kinase C, chelerythrine had no effect on PAF and A23187-induced platelet aggregation. These data suggest that the synergism between PAF and A23187 in platelet aggregation involves activation of thromboxane and tyrosine kinase pathways.
Blood Platelets/*drug effects ; Calcimycin/*pharmacology ; Humans ; Indomethacin/pharmacology ; Ionophores/pharmacology ; Platelet Activating Factor/metabolism/*pharmacology ; Platelet Aggregation/*physiology ; Protein-Tyrosine Kinase/antagonists & inhibitors/*physiology ; Quinones/pharmacology ; Research Support, Non-U.S. Gov't ; Thromboxane A2/*physiology ; Verapamil/pharmacology

The present study aimed to investigate the role of platelet-activating factor (PAF) in progesterone synthesis and vascular endothelial growth factor (VEGF) expression in rat luteal cells. Immature (25-28 days old) female Sprague-Dawley rats were injected subcutaneously with 50 IU pregnant mare serum gonadotrophin (PMSG), and 25 IU human chorionic gonadotrophin (hCG) 48 h later, to induce follicular development and luteum formation. On day 6 after hCG administration (the day of hCG administration was the first day), the rats were killed by guillotine and the ovarian luteal cells were collected. After incubation for 24 h, luteal cells were incubated without or with different doses (0.1 μg/mL, 1 μg/mL, 10 μg/mL) of PAF at 37 °C (5% CO(2)) for 24 h, and then progesterone concentration was evaluated by radioimmunoassay (RIA); apoptotic rate and VEGF mRNA expression in luteal cells were assessed by flow cytometry and RT-PCR, respectively. The results showed that PAF promoted progesterone production, with a maximal effect at 1 μg/mL (P<0.05); PAF increased apoptotic rate but not in a dose-dependent manner, and 10 μg/mL PAF enhanced apoptotic rate significantly (P<0.05); furthermore, PAF stimulated VEGF mRNA expression in luteal cells, especially at 1 μg/mL (P<0.01). It is suggested that PAF regulates progesterone synthesis and VEGF mRNA expression in luteal cells to mediate corpus luteum formation in rat ovary.
Animals ; Chorionic Gonadotropin ; pharmacology ; Corpus Luteum ; drug effects ; Female ; Luteal Cells ; drug effects ; metabolism ; Platelet Activating Factor ; pharmacology ; Pregnancy ; Progesterone ; biosynthesis ; Rats ; Rats, Sprague-Dawley ; Vascular Endothelial Growth Factor A ; metabolism

This study was designed to investigate the effects of platelet activating factor (PAF) on the action potential and potassium currents in guinea-pig ventricular myocytes. Whole cell patch clamp techniques were used. With 5 mmol/L ATP in the pipette electrode(mimic normal condition), 1 micromol/L PAF increased APD(90) from 225.8+/-23.3 to 352.8+/-29.8 ms (n=5, P<0.05), decreased I(K1) and I(K) tail currents from -6.1+/-1.3 to -5.6+/-1.1 nA (n=5, P<0.05) at -120 mV and from 173.5+/-16.7 to 152.1+/-11.5 pA (P<0.05, n=4) at +30 mV, respectively. But PAF had no effect on I(K1) at potentials within the normal range of membrane potentials (between -90 mV and +20 mV). In the contrary, without ATP in the pipette electrode by which I(K.ATP) was activated (mimic ischemic condition), 1 micro mol/L PAF shortened APD(90) from 153+/-24.6 to 88.2+/-19.4 ms (n=5, P<0.01). Incubation of myocytes with 1 micro mol/L glibenclamide, a blocker of I(K.ATP ) could restore prolongation of APD induced by PAF. In conclusion, in guinea-pig ventricular myocytes, with 5 mmol/L ATP in the pipette PAF could prolong APD partly due to the inhibition of I(K); while with 0 mmol/L ATP in the pipette, PAF could induce an activation of I(K.ATP), hence a decrease in APD. It is suggested that PAF may amplify the heterogeneity between ischemic and normal cardiac myocytes during ischemia /reperfusion, which may play a vital role in the pathogenesis of the arrhythmias induced by ischemia /reperfusion.
Action Potentials ; drug effects ; Adenosine Triphosphate ; pharmacology ; Animals ; Glyburide ; pharmacology ; Guinea Pigs ; Heart Ventricles ; cytology ; metabolism ; Myocytes, Cardiac ; metabolism ; physiology ; Patch-Clamp Techniques ; Platelet Activating Factor ; pharmacology ; Potassium Channels ; drug effects

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.
Diltiazem/pharmacology ; Dose-Response Relationship, Drug ; Drug Synergism ; Estrenes/pharmacology ; Flavones/pharmacology ; Human ; In Vitro ; Indomethacin/pharmacology ; Kinetics ; Mitogen-Activated Protein Kinases/metabolism ; Phosphorylation/drug effects ; Platelet Activating Factor/*pharmacology ; Platelet Activation/drug effects ; Platelet Aggregation/*drug effects/physiology ; Pyrrolidinones/pharmacology ; Serotonin/*pharmacology ; Thromboxane A2/biosynthesis ; Verapamil/pharmacology

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.
Diltiazem/pharmacology ; Dose-Response Relationship, Drug ; Drug Synergism ; Estrenes/pharmacology ; Flavones/pharmacology ; Human ; In Vitro ; Indomethacin/pharmacology ; Kinetics ; Mitogen-Activated Protein Kinases/metabolism ; Phosphorylation/drug effects ; Platelet Activating Factor/*pharmacology ; Platelet Activation/drug effects ; Platelet Aggregation/*drug effects/physiology ; Pyrrolidinones/pharmacology ; Serotonin/*pharmacology ; Thromboxane A2/biosynthesis ; Verapamil/pharmacology