Effect of pyridoxal-5-phosphate in gel filtered blood platelets

The inhibitory effect of pyridoxal-5-phosphate [PLP] on gel filtered platelets [GFP] function has been studied. Prior addition of PLP caused inhibition of platelet aggregation and 5-HT, induced by ADP thrombin. The results showed no significant change in the formation of inositol triphosphate [IP3], due to phosphoinositides hydrolysis and of ADP induced platelets in the presence of PLP. ADP did not cause any decrease in the level of radioactivity of the phospholipids fraction nor an increase in the arachidonate metabolites from platelets treated with PLP. Prostagl and in synthetase activity was also examined and found to be not affected by PLP. The results also showed that PLP may exert its inhibitory effect by blocking the release of arachidonate but not its metabolism

Effect of dietary supplementation with pyridoxal-5-phosphate and polyunsaturated fatty acids on rat blood platelet function

Platelets were isolated from the blood of rats fed on st and ard laboratory diets and rats fed on supplements of pyridoxal-5-phosphate [PLP] and polyunsaturated fatty acids [PUFA] alone or in combination. Platelet counts and their protein and total lipid content were unaltered by the regimes. Rats fed on PUFA showed a significant increase in the linoleic acid content of the phospholipid fraction of platelets [p <0.001]. Dietary supplementation for one week with PLP or PUFA alone or in combination significantly prolonged the clotting time of freshly drawn blood, decreased the extent of ADP-induced aggregation, the release of platelet 5-hydroxytryptamine [5-HT] and the formation of thromboxane B2 [TXB2]. Furthermore, platelets isolated from rats fed on dietary supplements were more sensitive to inhibition of aggregation by PLP in vitro, and their aggregation by collagen was not similarly affected. These results pointed to a direct and specific inhibitory action of PLP on ADP-induced aggregation of blood platelets