Thrombin stimulates Na+‐H+ exchange across the human platelet plasma membrane

Abstract

We have investigated the release of protons from thrombin‐stimulated platelets. Addition of thrombin to suspensions of washed platelets resulted in fast liberation of H⁺. In the presence of 0.1 mM amiloride, a potent inhibitor of the Na⁺/H⁺ transport system, the amount of protons liberated was decreased by about 50%, and was further reduced to about 15% by 1 mM amiloride. Similar inhibition of H⁺ release was observed after Na⁺ in the incubating medium had been replaced by choline. We conclude that one of the earliest events in thrombin‐stimulated platelets consists of the activation of an Na⁺/H⁺ countertransport, which leads to an increase in intracellular pH.