The inhibitory effects of okadaic acid on platelet function. |
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Authors: | M Higashihara K Takahata K Kurokawa M Ikebe |
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Institution: | First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. |
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Abstract: | Okadaic acid (OA), a potent inhibitor of protein phosphatases type 1 and type 2A, inhibited thrombin-induced platelet aggregation (IC50 = 0.8 microM), 14C]serotonin release and increase in intracellular Ca2+ (Ca2+]i) in the same dose dependence. In the absence of thrombin OA increased the phosphorylation of 50-kDa protein and 20-kDa myosin light chain (MLC20). The 50-kDa protein phosphorylation was accomplished within a shorter time period and at a lower concentration than was the MLC20. OA decreased the thrombin-induced phosphorylation of 47-kDa protein and MLC20, although phosphorylation of MLC20 reincreased at higher concentrations of OA (5-10 microM). Since type 2A phosphatase is more sensitive to OA than type 1, these results suggest that type 2A phosphatases are involved in the regulation of Ca2+ signaling in thrombin-induced platelet activation. |
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