The role of the actin status in platelet behaviour

The status of platelet actin has been studied analytically by the DNase-I inhibition assay. Exposure of platelets to diamide, which oxidizes sulphydryl groups, results in an increase of filamentous actin. Neutralization of the effect of diamide by addition of 2-mercaptopropionylglycine (2-MPG) or washing out the excess of diamide is associated with a normalization of the cellular actin status. These findings strongly suggest that the redox state of platelets is somehow involved in the process of actin polymerization. Alterations of the redox state in metabolically altered platelets could therefore account for changes in the G- to F-actin equilibrium. In the thrombin-induced actin polymerization the redox state of the cell seems to be not involved, since 2-MPG preincubation of platelets (1.25 mM, 30 min) does not inhibit the filament assembly.