thromboxane-a2 and ferric-chloride

The aim of our study is to elucidate whether experimental arterial thrombosis is regulated by physiological doses of androgen and its receptor via modulation of platelet activation.. Surgical castration was performed in male rats and ferric chloride (FeCl(3)), as a stimulator, induced the experimental arterial thrombosis. Testosterone was measured directly by chemiluminescent immunoassay on the Bayer ADVIA Centaur analyzer. Dihydrotestosterone (DHT) was determined by ELISA using a commercially available kit. A platelet aggregometer was used to assess aggregation, and a platelet adherometer was used to measure adhesion. The contents of TXB(2) and 6-Keto-PGF(1alpha) were assayed by radio-immunoassay using commercially available kits.. Our data showed that DHT replaced restored circulating DHT of castrated rats to physiological levels, without being altered by treatment with flutamide. Castration caused significant increases in the thrombus area and weight in castrated rats as compared with control group. In PRP diluted with autologous PPP, ADP-induced platelet aggregation rate was only 9.10%. However, in PRP diluted with Tyrode's buffer, 1 microM ADP-induced platelet aggregation rate rose to 63.65%. In PRP diluted with Tyrode's buffer, and pretreated with DHT (1 nM, 2 nM), ADP-induced platelet aggregation was significantly lowered again. Platelet aggregation in PRP diluted with autologous PPP was enhanced in castrated rats as compared with sham-operated rats, and DHT (2 nM) replacement suppressed platelet aggregation in castrated PRP to the level similar to that of sham-operated rats. However, presence of flutamide (3 microM) significantly increased platelet aggregation in PRP diluted with autologous PPP or Tyrode's buffer. DHT (2 nM) replacement significantly inhibited the ADP-induced platelet adhesion. However, presence of flutamide (3 microM) increased ADP-induced platelet adhesion again. DHT replacement obviously reduced the ratio of TXB(2) to 6-keto-PGF(1alpha) in castrated rats. However, administration of flutamide and DHT to castrated rats caused an increase in the ratio of TxB(2) to 6-keto-PGF1alpha.. Inhibition of experimental arterial thrombosis by androgen at physiological doses and its receptor is mediated via modulation of platelet activation.

Topics: 6-Ketoprostaglandin F1 alpha; Androgens; Animals; Arteries; Castration; Chlorides; Dihydrotestosterone; Ferric Compounds; Male; Platelet Activation; Platelet Adhesiveness; Platelet Aggregation; Rats; Receptors, Androgen; Testosterone; Thrombosis; Thromboxane A2

Platelets stably interact with collagen via glycoprotein (GP)VI and alpha2beta1integrin. With alpha2-null mice, we investigated the role of alpha2beta1 in thrombus formation and stability in vivo and in vitro. Using a FeCl(3)-induced thrombosis model, in arteries from alpha2-null mice smaller thrombi were formed with more embolization compared to vessels from wild-type mice. Aspirin treatment of wild-type mice causes similar effects, while the thromboxane A(2) analogue U46619 was borderline effective in suppressing the embolisation in alpha2-null mice. In vitro, perfusion of alpha2-null blood over collagen resulted in formation of thrombi that were smaller and looser in appearance, regardless of the presence or absence of coagulation. Aspirin treatment or blockage of thromboxane receptors provoked embolus formation in wildtype blood, while U46619 normalized thrombus formation in blood from alpha2-null mice. We conclude that integrin alpha2beta1 plays a role in stabilizing murine thrombi, likely by enhancing GPVI activation and thromboxane A(2) release. The increased embolization in alpha2-null mice may argue against the use of alpha2beta1 integrin inhibitors for antithrombotic therapy.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aspirin; Chlorides; Collagen; Ferric Compounds; Integrin alpha2beta1; Mice; Mice, Knockout; Thromboembolism; Thrombosis; Thromboxane A2

The present study was designed to elucidate the role of p38 mitogen-activated protein kinase (p38) in thrombus formation. We used p38alpha heterozygous (p38alpha+/-) mice and used ferric chloride (FeCl3)-induced carotid artery injury as a model of thrombus formation. The time to thrombotic occlusion induced by FeCl3 in p38alpha+/- mice was prolonged compared to that in wild-type (WT) mice. Platelets prepared from p38alpha+/- mice showed impairment of the aggregatory response to a low concentration of U46619, a thromboxane A2 analogue. Furthermore, platelets prepared from p38alpha+/- mice and activated by U46619 were poorly bound to fibrinogen compared with those from WT mice. Both the expression and activity of tissue factor induced by FeCl3 in WT mice were higher than those in p38alpha+/- mice. These results suggest that p38 plays an important role in thrombus formation by regulating platelet function and tissue factor activity.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Alleles; Animals; Blood Coagulation; Blood Platelets; Chlorides; Ferric Compounds; Fibrinogen; Heterozygote; Homozygote; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; p38 Mitogen-Activated Protein Kinases; Placenta; Platelet Adhesiveness; Protein Binding; Protein Isoforms; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thromboplastin; Thrombosis; Thromboxane A2; Time Factors; Vasoconstrictor Agents