Vascular endothelial growth factor (VEGF) stimulates angiogenesis, vasodilatation and increased vascular permeability. VEGF exerts these effects by increasing intracellular calcium concentration ([Ca²⁺]_i) in endothelial cells (Bates, et al. 1999). It has been suggested that calcium influx into endothelial cells probably is through transient receptor potential (TRP) channels. So far, seven canonical TRP (TRPC) channels have been isolated (Trebak et al, 2003). Among them, TRPC3, 6 and 7 are considered to be directly activated by the signalling molecule, diacylglycerol (DAG). The aim of the present study was to determine whether VEGF could activate cation entry through VEGF receptor 2 (VEGF-R2) mediated activation of TRPCs in the Human Microvascular Endothelial Cells (HMVECs). Pooled dermal HMVECs were obtained at passage 3, propagated in microvascular endothelial cell medium 2 (EGM-2 MV Bulletkits, Clonetics), and used up to passage 5. Whole cell currents were recorded at ambient temperature from HMVECs. The bath solution contained (in mM) 140 NaCl, 5 CsCl, 0.05 CaCl₂, 1 MgCl₂, 10 glucose, and 10 HEPES (pH 7.4 with NaOH). The pipette solution contained (in mM) 110 caesium methanesulfonate, 25 CsCl, 2 MgCl₂, 3.62 CaCl₂, 10 EGTA, 30 HEPES (pH 7.2 with CsOH) with a calculated free [Ca²⁺] of 100 nM. Cells were held at a potential of -60 mV, and current-voltage (I-V) relations were obtained every 5 s, using 400 ms duration voltage ramps between -100 and +100 mV (Jung et al. 2002). VEGF (1 nM) increased net inward and outward current during applied voltage ramps (from -2.76±0.81 to -5.22±1.54 pA/pF at -100 mV, P<0.05; and from 5.06±1.15 to 16.32±4.13 pA/pF at +100 mV, P<0.01, means±SE, n=13 cells, Cm=44.69±7.20 pF). The VEGF-activated current was outwardly rectifying, exhibited a reversal potential close to 0 mV (-5.61±1.93 mV, n=13), and was inhibited by gadolinium chloride (100 μM) (from -6.08±2.54 to -2.64±1.16 pA/pF at -100 mV, P<0.05; and from 20.10±6.10 to 7.49±3.05 pA/pF at +100 mV, P<0.01, n=7). Replacement of external cations with N-methyl-D-glucamine (NMDG) abolished the inward component of the current (from -7.07±3.57 to -2.92±1.92 pA/pF at -100 mV, P<0.05, n=5), demonstrating a cation non-selective current. A similar current was also activated by application of the DAG analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG) (100 μM; n=4). The VEGF -activated currents were similar to those recorded from VEGF-R2 and TRPC3 or TRPC6 doubly-transfected Chinese Hamster Ovary cells (Cheng et al, 2004). Collectively, these findings constitute the first evidence that VEGF and OAG activated a Gd³⁺-sensitive, TRPC-like current in HMVECs.