Inhibitory action of soluble elastin on thromboxane B2 formation in blood platelets |
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Authors: | Keizo Sekiya Hiromichi Okuda |
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Institution: | Department of Medical Biochemistry, School of Medicine, Ehime University, Shigenobu, Onsen - gun, Ehime 791-02, Japan |
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Abstract: | Soluble elastin, prepared from insoluble elastin by treatment with oxalic acid or elastase, was found to inhibit the formation of thromboxane B2 both from 1-14C]arachidonic acid added to washed platelets and from 1-14C]arachidonic acid in prelabeled platelets on stimulation with thrombin. In both systems, the formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) was accelerated. Oxalic acid-treated soluble elastin st 1 and 10 mg/ml inhibited the formation of thromboxane B2 from exogenously supplied arachidonic acid 21 and 59%, respectively, and the formation of thromboxane B2 in prelabeled platelets stimulated by thrombin 44 and 94%, respectively. These concentrations of elastin increased the formation of 12-HETE from exogenously supplied arachidonic acid about 3.4- and 7.3-times, respectively. Almost all the added arachidonic acid was converted to metabolites. In prelabeled platelets, soluble elastin at 1 and 10 mg/ml increased the formation of 12-HETE stimulated by thrombin about 1.3- and 2.8-times, respectively, and inhibited the thrombin-induced total productions of thromboxane B2 (12-hydroxy-5,8,10-heptadecatrienoic acid (12-HETE) and free arachidonic acid by 26 and 25%, respectively. Elastase-treated digested elastin also inhibited the formation of thromboxane B2 and stimulated the formation of 12-HETE in prelabeled platelets stimulated by thrombin. This inhibitory action of elastin was not replaced by desmosine. The level of cAMP in platelets was not affected by soluble elastin. Soluble elastin was also found to inhibit platelet aggregation induced by thrombin. However, the inhibitory action of soluble elastin on platelet aggregation cannot be explained by inhibition of thromboxane B2 formation by the elastin. |
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Keywords: | Elastin Platelet aggregation Arachidonic acid Hepes EGTA 12-HETE 12-hydroxy-5 8 10 14-eicosatetraenoic acid HHT 12-hyroxy-5 8 10-heptadecatrienoic acid |
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