Movement of sodium into human platelets

Abstract

Addition of ADP induces platelets in plasma to undergo shape change from a disc to a spiny sphere and to develop adhesiveness, i.e. to aggregate. The aggregation of human platelets by ADP is associated with a net uptake of Na +. The present experiments demonstrate that the induction of shape change by ADP in acidified or EGTA-treated plasma conditions which inhibit aggregation, is also associated with a movement of Na + into platelets. When ADP-induced platelet shape change and aggregation is inhibited by prostaglandin E 1 Na + uptake is also blocked. Platelets aggregated by epinephrine do not take up Na +. In a manner analogous to the effect of ADP, polylysine also induces Na + uptake during aggregation. Vasopressin, in a manner analogous to epinephrine, induces aggregation without Na + uptake. The increase in platelet Na + resulting from ouabain inhibition of Na + efflux induces an increase in the aggregation response to ADP and to epinephrine.