Effects of VEGF on Ca(2+)-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 Ca(2+)-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 Ca(2+) in LEC. Pretreatment with 10(-5) M genistein or 5x10(-6) M herbimycin A produced a significant reduction of the VEGF-induced Ca(2+)-transient. In the presence of 10(-6) M thapsigargin, VEGF caused no significant effect on the Ca(2+)-transient. Pretreatment with Ca(2+)-free solution containing 0.1 mM EGTA produced no significant effect on the peak increase of Ca(2+) induced by 0.1 or 10 ng/ml VEGF, but significantly depressed the sustained part of Ca(2+) 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 3 x 10(-5) M N(omega)-nitro-L-arginine 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 Ca(2+) from the inositol 1,4, 5-triphosphate-sensitive intracellular Ca(2+) stores in LEC. VEGF(165) also produces endothelium-dependent nitric oxide-mediated dilation of the precontracted isolated lymph vessels.