Desensitization of human platelets by platelet activating factor.

Human platelets are less responsive to PAF at 37 degrees than at 25 degrees. They can be desensitized to the effects of PAF by pre-exposure to small concentrations. In both cases desensitization appears to be accompanied by a decreased affinity of the high affinity site for PAF rather than loss of binding sites. Alteration of a metabolic step subsequent to binding cannot be excluded, but platelets show normal response to a variety of other agents under the conditions resulting in desensitization of platelets to PAF.