INHIBITORY EFFECT OF FLAVONOLS OF CARTHAMUS TINCTORIUS L. AGAINST RABBIT PLATELET ACTIVATION INDUCED BY PLATELET ACTIVATING FACTOR

AIM To observe the inhibitory effect of myricetin (Myr) and kaempferol (Kae) (components of Carthamus tinctorius L.) against washed rabbit platelet (WRP) aggregation, 5-HT release and intercellular free calcium concentration elevation induced by platelet activating factor (PAF). METHODS The platelet aggregation induced by PAF was determined with turbidity assay. The platelet 5-HT release and platelet inner free calcium concentration elevation induced by PAF were measured by OPT fluorescence assay and Fura-2/AM probe fluorescent technique respectively. RESULTS The WRP aggregation and 5-HT release induced by PAF (9.55×10^-9mol·L^-1) were both inhibited by Myr and Kae in a concentration dependent manner. WRP aggregation rate can be significantly decreased by Myr and Kae. Low concentration Kae (21.8 μmol·L^-1) showed no inhibition effect against platelet aggregation. The IC₅₀ of Myr and Kae against WRP aggregation were 17.5 μmol·L^-1 and 73.7 μmol·L^-1 respectively. It was shown by OPT fluorescence assay that Myr (7.86 μmol·L^-1) and Kae (21.8 μmol·L^-1) were not effective against platelet 5 HT release (P>0.05). The IC₅₀ of Myr was 64.1 μmol·L^-1 and that of Kae was 128 μmol·L^-1. It was also found that the platelet inner free calcium concentration elevation evoked by PAF (4.78×10^-10mol·L^-1) was inhibited by Myr and Kae. CONCLUSION The rabbit platelet activation induced by platelet activating factor can be inhibited by Myr and Kae.