Agonist-specific desensitization of shape change of platelets

Using scanning electron microscopy and light scattering we have investigated the shape change of bovine platelets. The extents of shape change obtained by ADP and 5-hydroxytryptamine(5HT) increased in dose-dependent manner, and the maximum obtained by these agonists were additive. The agonist-specific desensitization in shape change was observed with ADP, 5HT and thrombin. The extent of desensitization by pre-exposure to ADP was dependent upon the concentration of ADP. It was strongly indicated that receptors or their subsequent stimuli-transmission apparatus became unable to respond to further stimulation after the exposure to the initial stimulation.