[Calcium mobilizing effect of hawthorn leaf procyanidins in vascular endothelial cells].

The hawthorn leaves have the effect of activating blood, removing blood stasis, regulating qi through the veins, dissolving turbidity and lowering lipid. Procyanidinis is one of its main active components and plays an important role in regulating vasoactivity. Previous studies showed that the regulating effect of procyanidins was related to its regulation on nitric oxide secretion from vascular endothelial cells, and this effect was dependent on the extracellular calcium concentration, suggesting that the changes in intracellular calcium ion concentration in endothelial cells may play a key role in this process. However, the research on this issue is still insufficient so far. This study is aimed to observe the effect of hawthorn leaf oligomeric procyanidins (HLP) on calcium mobilization of vascular endothelial cells, and investigate the underlying mechanism. Human umbilical vein endothelial cells (HUVEC) were cultured and labeled with Fura-2. HUVEC were treated with HLP at concentrations of 6.25, 12.5, 25 and 50 mg·L⁻¹, and the intracellular calcium concentrations were measured with a living cell microscope for 30 min. HLP increased the intracellular calcium concentration of HUVEC in a concentration dependent manner; and the intracellular calcium concentrations in 25 and 50 mg·L⁻¹ HLP groups were significantly higher than that in the normal group. With the use of calcium-free incubation buffer, addition of calcium chelating agent EGTA in incubation buffer, or use of inhibitors for sodium calcium exchanger, the effect of HLP was significantly inhibited. On the other hand, the effect of HLP could also be weakened by inhibiting the calcium release from the intracellular storage. In conclusion, these results suggest that HLP can elicit calcium mobilization in vascular endothelial cells, which may be one of the mechanisms for its vascular modulatory activity; and this calcium mobilizing effect may be achieved through promoting both extracellular calcium influx and intracellular calcium release, additionally the former may be related to activating the reverse transport of Na⁺-Ca²⁺ exchangers on the cell membrane.