[Roles of intercellar Ca2+ and protein kinase C played in tissue factor pathway inhibitor and tissue factor...

The purpose of the present study was to elucidate the roles that protein kinase C (PKC) and calcium played in the tissue factor (TF) synthesis and tissue factor pathway inhibitory (TFPI) release in human umbilic vein endothelial cells (HUVEC). A23187 was used to represent calcium ionophore and phorbol 12-myristate 13-acetate (PMA) as that of PKC activator. TF activity in the lysed HUVEC was measured using one stage clotting assay. TFPI activity in the conditioned medium of HUVEC was assessed by the two-step chromogenic method. The results showed that the TF activities in A23187, PMA and A23187 + PMA groups were remarkably higher (P < 0.01) than that in control. Among the three treated groups, the TF activities in both A23187 group and A23187 + PMA group were lower than that in the PMA group (P < 0.05), but the difference between the former two groups was statically insignificant (P > 0.05). In contrast to the control group, the TFPI activity in the A23187 group was not statistically different (P > 0.05). However, the TFPI activities in the PMA group and the A23187 + PMA group were markedly higher than those in the control group and the A23187 group (P < 0.01). These findings indicate that PKC and calcium ion promote TF synthesis in HUVEC but the effect of the former is stronger than that of the latter, and that the release of TFPI from HUVEC is facilitated by PKC and not significantly affected by calcium ion.