Stimulation of human platelet aggregation by phospholipase-A and a saline "extract" of a polyurethane.

A saline extract of polyurethane (SPU) induces enzymatic conversion of arachidonic acid (either exogenous or released through the action of exogenous phospholipase-A) by activating a hitherto undiscovered labile enzyme, synthetase-alpha which is not blocked by aspirin. Addition of SPU, plus arachidonic acid or SPU plus phospholipase-A to platelet-rich plasma (PRP) triggers a biphasic platelet aggregation. Incubation of SPU with PRP results in activation and exhaustion of synthetase-alpha; this renders platelets refractory to the various aggregating agents.