Pyridoxal phosphate inhibition of platelet function

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Abstract
The effect of pyridoxal phosphate (PLP) on human platelet function in vitro was studied. PLP inhibited ADP-induced shape change, aggregation and the potentiation by ADP of arachidonic acid-induced aggregation. This inhibition could easily be reversed by increasing concentrations of ADP or by removing PLP. Addition of sodium borohydride to PLP treated platelets produced irreversible inhibition of ADP aggregation. PLP apparently inhibited ADP-induced platelet function by forming a Schiff base with platelet-surface amino groups. PLP also produced a partial inhibition of platelet aggregation to epinephrine, arachidonic acid, A23187 and a dose-dependent inhibition of [14C]serotonin release to epinephrine and arachidonic acid. PLP did not inhibit [14C]-serotonin release to A23187, nor did it suppress arachidonic acid-induced malondialdehyde production. The partial inhibition by PLP of platelet aggregation observed to epinephrine, arachidonic acid and A23187 resulted from PLP inhibition of the effect of released ADP.