PLATELET-ADHESION, SHAPE CHANGE, AND AGGREGATION - RAPID INITIATION AND SIGNAL-TRANSDUCTION EVENTS

Blood platelets are essential for hemostasis, and knowledge of their f unction is important for understanding both normal and pathologic situ ations. A number of approaches have been used to evaluate platelet adh esion, aggregation, and secretion, and within the last 10 years much i nterest has been directed to the biochemical mechanisms and signal tra nsduction events occurring during these various phases of function. Ne w information has come from development of technologies to evaluate th e changes occurring immediately after platelet activation and consiste nt with the speed needed for hemostasis in the arterial circulation. U se of rapid flow and mixing technologies as seen in quenched-flow, con tinuous-flow, and stopped-flow devices has revealed that platelet aggr egation, shape change, adhesion, and secretion begin within 1 s and ma y be nearly complete by 5 s. Biochemical changes such as in protein ph osphorylation, calcium release, and phospholipid hydrolysis are clearl y evident in hundreds of milliseconds. Therefore, it is necessary to u nderstand these early events in signal transduction and to assess alte rations that may occur in diseases such as diabetes.