Endothelial glycocalyx is a gel-like structure present on the luminal surface of blood vessels [Weinbaum et al, Annu Rev Biomed Eng. 2007, 9:121:67]. Endothelial glycocalyx comprises proteoglycan core proteins, glycosaminoglycans (GAG) chains, sialoglycoproteins and contributes to the selective sieving action of the glomerular capillary wall. The endothelial glycocalyx is a critical determinant of permeability in kidney glomeruli. Disruption of the endothelial glycocalyx is linked with microalbuminuria in diabetes.Angiopoietin-1 is a paracrine growth factor synthesised by glomerular podocytes, that exerts paracrine actions on glomerular endothelail cells. Angiopoietin-1 decreases the ultrafiltration coefficient of single isolated glomeruli. In other capillary beds, parallel actions of angiopoietin-1 on hydraulic conductivity are mediated by increased depth of the endothelial glycocalyx. We have examined release of GAGs from the surface of human conditionally immortalized glomerular endothelial cells (ciGEnC) in vitro, and studied the effect of angiopoietin-1 on this process. Primary GEnCs, previously immortalised in our laboratory [Satchell et al, Kidney Int. 2006, 69 (9): 1633 – 1640] proliferate at 33°C, and differentiate to a non-proliferative quiescent state at 37°C. These ciGEnCs were differentiated and grown to 60-70% confluency, serum-starved for 3 hours, in the presence or absence of angiopoietin-1 (200ng/ml). After harvesting this supernatant, cell monolayers were exposed to either pronase (0.01%) or vehicle for 1 minute and the supernatant again aspirated. Harvested supernatant was added to an Alcian Blue solution, and the linear relation between GAG mass and decreased absorption of 488 nm light by Alcian Blue solution was used to quantify supernatant glycosaminoglycan content, referenced to known concentrations of GAG (chondroitin sulphate) standards. Supernatant GAG concentration was 72.57±39.65 (n=4) µg/ml from vehicle-treated endothelial cells, and significantly higher (150.3±61.81 (n=4) µg/ml) from pronase-treated endothelial cells (p<0.01, paired t-test). Supernatant harvested from endothelial cell monolayers exposed to angiopoietin-1 (90.94±21.89 µg/ml, n=3) demonstrated significantly higher GAG concentrations than supernatant from monolyers treated with serum-free media alone (50.35±13.73 µg/ml, n=3) (p<0.05, paired t-test). Increased GAG turnover by glomerular endothelial cells in response to angiopoietin-1 matches physiological data and studies in other capillary beds. The glycocalyx of glomerular endothelial cells thus appears modifiable by endogenous, paracrine agents.