The rapid polyphosphoinositide metabolism may be a triggering event for thrombin-mediated stimulation of human platelets |
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Authors: | A Imai S Nakashima Y Nozawa |
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Affiliation: | Department of Biochemistry Gifu University School of Medicine Tsukasamachi-40, Gifu 500, Japan |
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Abstract: | The metabolism of polyphosphoinositides was examined in human platelets activated by thrombin. The addition of thrombin to [3H]glycerol-labeled platelets induced an initial loss and a subsequent increase of the radioactivity in phosphatidylinositol-4,5-bisphosphate (TPI) without any significant change in phosphatidylinositol-4-phosphate (DPI). A marked enhancement of [32P]Pi incorporation into TPI occurred in parallel with an increase in this lipid content, which was accompanied with a conccurent decrease in phosphatidylinositol (PI). The rate of this subsequent increase in TPI was smaller than that observed in [3H]arachidonic acid-labeled platelets, suggesting that formed TPI in activated platelets may contain much greater amount of arachidonate than preexisting TPI in resting platelets. These data indicate that thrombin causes a rapid change in TPI metabolism (initial degradation of preexisting TPI and subsequent production of arachidonate-rich TPI), which might be a primary candidate to modulate thrombin-induced function in human platelets. |
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Keywords: | PI phosphatidylinositol DPI phosphatidylinositol-4-phosphate TPI phosphatidylinositol-4,5-bisphosphate PA phosphatidic acid DG diacylglycerol PRP platelet-rich plasma HPTLC hihg performance thin-layer chromatography ATP adenosine triphosphate |
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