FP271
SYSTEMIC VESSEL DYSFUNCTION AS A CONSEQUENCE OF ALBUMINURIA - AN EXPLANATION FOR ACCELERATED VASCULAR DISEASE IN URAEMIA

Introduction and Aims: Patients with albuminuria have widespread endothelial dysfunction and increased microvascular permeability however the underlying mechanism remains unclear. To investigate these mechanisms we sought to use a combined confocal-fluorescent imaging method for assessing structural-functional relationships between glycocalyx and albumin flux (P_sBSA) in systemic mesenteric microvessels of rats with and without acute albuminuria in vivo.

Methods: A single tail vein injection of monoclonal anti-nephrin (5-1-6) antibody or heat inactivated sham controls were used to induce podocyte specific albuminuria in female Lewis rats. Following the onset of albuminuria (5 days), the mesenteric microvessels of pentobarbitone-anaesthetised rats were cannulated using double barrel theta style micropipettes where the pressure on either side was set so that only one desired side perfused. The pressures in the pipette were switched instantly to change from perfused unlabeled 4% BSA to perfused Alexa 488 labeled BSA and back, which was imaged using fluorescent microscopy to calculate Ps_BSA. Endothelial glycocalyx depth was then quantified by changing the perfusate to trimethylamino-diphenylhexatriene (TMA-DPH: membrane label) and tetramethylrhodamine-isothiocyanate-conjugated Wheat Germ Agglutinin (TRITC-WGA lectin: EG-SL label), and imaged using Confocal Microscopy. Glycocalyx depth was estimated based on the anatomical distance between peak fluorescence of TRITC-WGA and TMA-DPH signals.

Results: Albuminuric rats demonstrated a significantly reduced mesenteric microvascular glycocalyx depth (peak-peak) when compared to sham treated healthy controls (p < 0.05, unpaired t-test) following the onset of acute albuminuria (p < 0.001, two-way ANOVA) and this reduction in depth was linearly correlated to a significant increase in P_sBSA (p < 0.05, Pearson’s correlation) (p < 0.05, unpaired t-test).

Conclusions: These findings suggest that widespread loss of endothelial glycocalyx and increased microvascular permeability in systemic non-renal microvessels is a consequence of all-cause albuminuria and that glycocalyx provides the structural mechanistic link between these widespread functional pathologies. To our knowledge this is the first in vivo data identifying a rapid systemic micro-vessel dysfunction resulting from a primarily glomerular injury and suggests the mechanism of this feedback-loop requires further investigation.