The state of actin in activated human platelets.

The state of platelet actin was determined using a fluorescent method of DNAse I inhibition. Activation of human platelets resulted in mobilization of DNAse-available actin. When platelets were activated with ADP the change in the state of actin was gradual and preceded the secretion. When thrombin was used as an activator, a sharp and rapid decrease in the DNAse-available actin was observed which paralleled the secretion. Inhibition of ADP-induced aggregation (and secretion) by EDTA resulted in a decrease in the rate of change on actin. Inhibition of the thrombin-induced aggregation (but not secretion) by EDTA did not affect the change in the state of actin.