In vitro binding of inorganic mercury to the plasma membrane of rat platelet affects Na+-K+-ATPase activity and platelet aggregation

Hg-2+ binding to ouabain-sensitive Na+-K+-ATPase of rat platelet membrane was specific with a K-a of 1.3x10(9) moles and B-max of 3.8 nmoles/mg protein. The binding of mercury to Na+-K+-ATPase also inhibits the enzyme significantly (P <0.001), which is greater than its ouabain sensitivity. Further in the cytosol of washed platelets conjugation of reduced glutathione (GSH) to Hg2+ is correlated dose dependently (25, 50 and 100 pmoles) to enhanced GSH-S-transferase (GST) activity. It may be concluded from the present in vitro experiments that mercury binds specifically to thiol groups present in the platelet membrane Na+-K+-ATPase, inhibits the enzyme and induces changes in platelet function, namely, platelet aggregation by interfering with the sodium pump.