Effect of lanthanum ion on platelet electrophoretic mobility.

The effect of trivalent La ions on the elctrophoretic mobility of washed human platelets has been studied. The mobility of the human platelet in 0.145 M sodium chloride at pH 7.2 was -0.84 +/- 0.06 micron per sec per volt per cm with an isoelectric point approximately at pH 3.4 La3+ at a concentration corresponding to the physiological level of Ca2+ changed the sign of the electrophoretic mobility of the platelets at pH 5.5 and pH 4.0, but had only a faint or practically no effect at pH 3.0 and pH 2.0. It is assumed that La 3+ exerts its effect when bound to the phosphate groups on the surface.