Pre-eclamptic toxaemia (PET) is characterised by maternal hypertension and proteinuria due to widespread endothelial dysfunction (1). PET plasma induces endothelial junctional breakdown and permeability modulation (2). Altered circulating vascular endothelial growth factors (VEGF) placental growth factor (PlGF), VEGF165a and VEGF165b may contribute to endothelial dysfunction (3). Flt-1 receptor coated ELISA plates were co-incubated with biotinylated-VEGF165b, and PlGF or non-biotinylated-VEGF165b. Percentage optical density (OD) was recorded. 0.4μm pore polyester membrane transwells seeded with human umbilical vein endothelial cell (HUVEC) monolayer were exposed to FITC-BSA (1mg/mL) tracer and incubated with VEGF165a, followed by VEGF165b and PlGF for 2 hrs. Membranes were fixed and probed for VE-cadherin junctions. Tracer samples were collected over time and OD recorded. VE-cadherin junctions were visualised via fluorescence microscopy and quantified by percentage junction gaps, thin connecting junctions, or thick connecting junctions. Values are expressed as mean ± SEM, compared by ANOVA. Co-incubation with non-biotinylated-VEGF165b and PlGF decreased biotinylated-VEGF165b to Flt-1 binding (p<0.0001, n=4). PlGF co-incubation further decreased biotinylated-VEGF165b binding, resulting in an IC50 of 18.37nM ± 0.25 vs. 38.15nM ± 0.84 (p<0.0013, n=4). VEGF165a increased FITC-BSA OD after 2 hrs (1.85 ± 0.23OD) (p<0.0001, n=4), but not VEGF165b (0.77 ± 0.09OD) (p>0.05, n=4) or PlGF (0.93 ± 0.25OD) (p>0.05, n=2) vs. vehicle (0.77 ± 0.06OD). VEGF165b inhibited VEGF165a-induced permeability (0.99 ± 0.15OD) (p<0.01, n=3), but not PlGF (1.72 ± 0.18OD) (p>0.05, n=3). PlGF co-incubated with VEGF165b abolished VEGF165a permeability rescue (2.07 ± 0.15OD) (p>0.05, n=2). VE-cadherin expression after 2 hours revealed increased gaps and decreased thin junction percentage after VEGF165a (Gaps: 49.14 ± 6.52%/Thin: 20.95 ± 1.57%) (p<0.01, n=4), but not VEGF165b (Gaps: 26.52 ± 2.96%/Thin: 40.30 ± 5.79%) (p>0.05, n=4) or PlGF (Gaps: 28.05 ± 3.42%/Thin: 49.11 ± 0.24%) (p>0.05, n=2) compared to vehicle (Gaps: 23.50 ± 2.93%/Thin: 49.73 ± 4.57%). VEGF165a co-incubation with VEGF165b decreased gap and increased thin junction percentage (Gaps: 17.43 ± 0.52%/Thin: 41.38 ± 2.77%) (p<0.001, n=4), but not with PlGF co-incubation (Gaps: 62.68 ± 5.30%/Thin: 16.40 ± 0.44%) (p>0.05, n=2) compared to VEGF165a alone. Co-incubation with VEGF165a, VEGF165b and PlGF (Gaps: 55.87 ± 0.35/Thin: 20.41 ± 0.44) showed no significant difference in gap or thin junction percentage compared to VEGF165a alone (p>0.05, n=2). These observations indicate VEGF interplay resulting in endothelial permeability and junctional modulation, suggesting a possible role for circulating VEGF alterations in pre-eclampsia.