The optimal levels of vitamin B6 in platelet function and blood coagulation of rabbits

The optimal level of vitamin B6, in the form of pyridoxal-5-phosphate (PLP) , on the antithrombotic effect was investigated in the platelet function an d blood coagulation of rabbits. Platelet aggregations induced with differen t agonists, including adenosine diphosphate (ADP, 2.4x10(-4) M), collagen ( 0.25 mg/ml), and thrombin (0.3 NIH unit/ml), were assessed in platelet-rich plasma (PRP) with PLP 0 to 3.0 mM. Thromboxane A2 (TxA2)-production of pla telet with PLP 0 to 2.4 mM was determined by radiochromatography using C-14 -arachidonic acid as precursor. The blood coagulation system was monitored by measuring thrombin time (TT), prothrombin time (PT), and partial thrombo plastin time (PTT) of plasma with PLP 0 to 2.0 mM. PLP significantly inhibi ted platelet aggregation to different agonists at the final concentration o f greater than or equal to 0.6 mM and reached the plateau of inhibition at greater than or equal to 1.8 mM. TxA2-production of PRP was significantly d ecreased at PLP greater than or equal to 0.36 mM and remained constantly at greater than or equal to 1.44 mM. PTT, PT, and TT were significantly prolo nged at PLP greater than or equal to 1.12 mM, greater than or equal to 1.44 mM, and > 1.44 mM, respectively. These results suggested that vitamin B6 d isplayed antiplatelet and anticoagulation action in rabbits at around 0.36 to 1.8 mM plasma level. (C) 1998 Elsevier Science Inc.