Role of cations on the platelet membrane GPIIb-IIIa complex

Abstract

It has been reported that the GPIIb and GPIIIa exist predominantly as the Ca²⁺-dependent, heterodimer complex, and incubation of intact platelets with EDTA at 37°C causes progressive dissociation of GPIIb-IIIa complexes. We used two monoclonal antibodies against GPIIb-IIIa complex (NNKY 1-32, NNKY 2-18) to study the effects of cations that influence the reassociation of dissociated GPIIb and GPIIIa, and studied the change of platelet aggregation under those conditions. Ca²⁺, Mg²⁺ and Mn²⁺ promoted the reassociation of dissociated GPIIb and GPIIIa in intact cells. But the promotive effect of Mn²⁺ on the reassociation of GPIIb and GPIIIa was less than that of Ca²⁺ and Mg²⁺. Ca²⁺ and Mg²⁺ also restored the aggregabilities of platelets, whereas Mn²⁺ did not. Differences were found in aggregability between samples. These results suggested that some different cations participate in the formation and maintenance of GPIIb-IIIa complex, and especially Ca²⁺or Mg²⁺ need for those conditions.