Platelet Shape Change and Cytoskeletal Assembly: Effects of pH and Monovalent Cation lonophores

Summary

The monovalent cation ionophores monensin and nigericin cause platelet shape change at a rate of approximately 1/20 of that caused by ADP. The effect of monensin was studied further. Shape change caused by monensin is pH dependent, increasing in rate as extracellular pH increases. Monensin induced shape change is not blocked by 30 μM cinanserin which completely inhibits serotonin induced shape change. Also, the amount of serotonin secreted by monensin treated platelets is below the threshold required to induce shape change. 100 μM ATP which inhibits ADP induced shape change does not affect monensin induced shape change. Amiloride, a sodium transport blocker, inhibits both the rate of ADP induced shape change and platelet spreading on poly-lysine coated glass. Amorphous platelet cyto-skeletons isolated from resting platelets at pH 6.8 with Mg^{+ +} but not Ca⁺⁺ can be transformed into filament bundles by subsequent incubation at pH 7.6. We conclude that platelet shape change is at least in part triggered by changes in cellular Na⁺ and pH

Keywords

Platelet shape change - Sodium - pH

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