Effects of VEGF on Ca2+-transient in cultured lymphatic endothelial cells and mechanical activity of isolated lymph vessels

We investigated the effects of vascular endothelial growth factor (VEGF(165)) on [Ca2+](i)-transient in cultured lymphatic endothelial cells (LEC) and mechanical activity of isolated dog thoracic ducts. VEGF (0.1-10 ng/ml) caused a dose-dependent increase of the [Ca2+](i) in LEC. Pretreatment with 10(-5) M genistein or 5x10(-6) M herbimycin A produced a significant reduction of the VEGF-induced [Ca2+](i)-transient. In the presence of 10(-6) M thapsigargin, VEGF caused no significant effect on the [Ca2+](i)-transient. Pretreatment with Ca2+-free solution containing 0.1 mM EGTA produced no significant effect on the peak increase of [Ca-2](i) induced by 0.1 or 10 ng/ml VEGF, but significantly depressed the sustained part of [Ca2+](i) observed at the higher concentration of VEGF. The VEGF (0.1-10 ng/ml) caused a significant dilation of the isolated lymph vessels with intact endothelium, which were precontracted with U46,619. The 10 ng/ml VEGF-induced dilation was significantly reduced by 3x10(-5) M N-omega-nitro-L-argjnine methyl ester (L-NAME). The action of L-NAME was inhibited by the simultaneous application of 10(-3) M L-arginine. Mechanical rubbing of the endothelium also caused significant inhibition of the VEGF-induced dilation. The findings suggest that VEGF(165) may activate the receptor-related tyrosine kinase and cause the release of Ca2+ from the inositol 1,4,5-triphosphate-sensitive intracellular Ca2+ stores in LEC. VEGF(165) also produces endothelium-dependent nitric oxide-mediated dilation of the precontracted isolated lymph vessels.