Desensitisation of human platelets against stimulation by thromboxane mimics--reduction in receptor capacity and loss of functional response.

Number and affinity of thromboxane A2/PGH2 receptors on gel-filtered human platelets was determined using the receptor antagonist 3H-SQ 29548 as a tracer compound. Preincubation of platelet rich plasma (PRP) with U 46619 reduced receptor number to 31% of control platelets without affecting the affinity (2 x 10(-9) mol/l). Pretreated platelets lost their reactivity to stimulation by U 46619 but not to thrombin within 3 h. It is concluded that preincubation of platelets leads to a homologeous platelet desensitisation and down regulation of thromboxane receptors.