VASCULAR ENDOTHELIAL GROWTH-FACTOR INDUCES EDRF-DEPENDENT RELAXATION IN CORONARY-ARTERIES

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), has recently been shown to increase cytosolic free calcium in endothelial cells. In the present study, we investigated the coronary vascular effects of recombinant human and native guinea pig VEGF/VPF in isolated canine coronary arteries in the presence and absence of intimal endothelium, indomethacin, and N(G)-monomethyl-L-arginine, a competitive nitric oxide synthase inhibitor. Addition of recombinant VEGF/VPF (1-660 pM) in coronary arteries that had been previously contracted with prostaglandin F2alpha induced a slow, dose-dependent relaxation, reaching a maximum of -59.1 +/- 6.7% (means +/- SE, n = 19). Mechanical disruption of the intimal endothelium completely abolished the observed relaxation. No direct vascular effect of recombinant VEGF/VPF on the endothelium-disrupted coronary arteries was noted. Pretreatment of endothelium-intact coronary arteries with 5 muM of indomethacin did not alter the observed relaxation (-57.3 +/- 7.0%, n = 18), whereas pretreatment with either N(G)-monomethyl-L-arginine or 10 muM of genistein, a known inhibitor of tyrosine kinase, significantly inhibited the relaxation. Addition of native VEGF/VPF (1-100 pM) also induced an endothelium-dependent relaxation in the isolated coronary arteries. Heating of recombinant VEGF/VPF (70-degrees-C, 25 min) or prior incubation with a specific antibody raised against a VEGF/VPF peptide completely abolished the relaxation. Finally, recombinant VEGF/VPF stimulated a slow rise in cytosolic free calcium in cultured human endothelial cells that was qualitatively similar to that of native VEGF/VPF. Collectively, these results show that VEGF/VPF, a tyrosine kinase-coupled endothelial growth factor, induces endothelium-dependent relaxation via the Ca2+-dependent synthesis and/or release of endothelium-derived relaxing factor.