Effects of vascular endothelial growth factor (VEGF) vascular permeability factor (VPF) on haemodynamics and permselectivity of the isolated perfused rat kidney

Background. Vascular endothelial growth factor (VEGF) or vascular permeability factor (VPF) is a selective mitogen for endothelial cells; it increases microvascular permeability and has been shown to relax isolated canine coronary arteries by an endothelium-dependent mechanism. In many tissues VEGF/VPF is expressed after an appropriate stimulus, mostly hypoxia. In the kidney VEGF/VPF is constitutively expressed in glomerular podocytes and epithelia of collecting duct. Glomerular and peritubular capillary endothelia also constitutively express specific VEGF receptors. The in vivo function of renal VEGF/VPF is unknown. Method. In the present study the effects of human recombinant VEGF(165), on renal haemodynamics and glomerular permselectivity was investigated in the isolated perfused kidney of the rat. Results. In kidneys preconstricted by noradrenaline (NA 1.5x10(-7) mol/l) VEGF/VPF (155 pmol/l) caused an almost complete return of renal perfusion flow rate to pre-NA values (before NA 113+/-4%, after NA 100%, 15 min with VEGF/VPF 111+/-4%). Shortly after VEGF/VPF administration VEGF/VPF-induced relaxation commenced, and became significant after 2 min (15 min with VEGF/VPF vs without VEGF/VPF 111+/-4% vs 103+/-2%; P < 0.05). In the presence of the NO-synthase inhibitor N-w-nitro-L-arginine (L-NNA; 5 x 10(-5) mol/l) VEGF/VPF caused only small, transient relaxations (before NNA 109+/-5%, after NNA 100%, 15 min with VEGF 95+/-2%). The cyclooxygenase inhibitor diclofenac failed to inhibit the relaxing activity of VEGF/VPF (before NA 119+/-4%, after NA+diclofenac 100%, 15 min with VEGF/VPF 123+/-5%). VEGF demonstrated no significant increase in renal protein excretion rate (after NA pretreatment (=100%): 12.5 min with VEGF/VPF vs without VEGF/VPF: 119+/-10% vs 132+/-11%, n.s.) (after NNA pretreatment (=100%) 12.5 min with VEGF/VPF vs without VEGF/VPF 94+/-5% vs 96+/-4%; n.s.) or clearance quotient of albumin. Glomerular filtration rate was not influenced by VEGF/VPF in kidneys pretreated with NA (before NA 105+/-5%, after NA 100%, 12.5 min with VEGF/VPF 94+/-2%) or with NNA (before NNA 107+/-6%, after NNA 100%, 12.5 min with VEGF/VPF 96+/-2%). Fractional glucose and fractional sodium excretion showed flow-dependent changes. Conclusion. VEGF/VPF can contribute to the relaxing capacity of the renal vasculature. This relaxation is partly mediated by the NO/endothelium-derived relaxing factor (EDRF) pathway. In the isolated perfused rat kidney the glomerular permeability for albumin is not affected by VEGF/VPF.