Effects of Thrombin on the Potassium and ATP Content of Platelets *

The blood platelets have many of the charac-teristics of living cells including an active metabo-lism. As in other cells, the concentration of po-tassium within platelets is high in comparison to that of extracellular fluid and- is similar to that of red blood cells (1). ATP also is present in high concentration within platelets (2) and is consid-ered to provide the energy necessary for clot re-traction, a process that requires metabolically ac-tive platelets (3). Unlike other cells, platelets are uniquely susceptible to the effects of thrombin, a proteolytic enzyme formed during clotting of blood. During coagulation, the platelets undergo a complex series of morphologic and biochemical changes (4), and there is a decrease in the concen-tration of some of the constituents of platelets, in-cluding potassium (1) and ATP (5). The pres-ent studies were designed to investigate some of the factors that influence changes in potassium and ATP within platelets. Methods All glassware with which platelets had contact was coated with silicone. ' Blood was drawn from normal human donors through 15-gauge, uncoated, disposable metal needles attached to plastic tubing and was collected in tubes containing an aqueous solution of the disodium * Submitted for publication February 26, 1964; ac-