The Endothelial Glycocalyx Prefers Albumin for Evoking Shear Stress-Induced, Nitric Oxide-Mediated Coronary Dilatation

Abstract

Background: Shear stress induces coronary dilatation via production of nitric oxide (NO). This should involve the endothelial glycocalyx (EG). A greater effect was expected of albumin versus hydroxyethyl starch (HES) perfusion, because albumin seals coronary leaks more effectively than HES in an EG-dependent way. Methods: Isolated hearts (guinea pigs) were perfused at constant pressure with Krebs-Henseleit buffer augmented with 1/3 volume 5% human albumin or 6% HES (200/0.5 or 450/0.7). Coronary flow was also determined after EG digestion (heparinase) and with nitro-L-arginine (NO-L-Ag). Results: Coronary flow (9.50 ± 1.09, 5.10 ± 0.49, 4.87 ± 1.19 and 4.15 ± 0.09 ml/min/g for ‘albumin’, ‘HES 200’, ‘HES 450’ and ‘control’, respectively, n = 5–6) did not correlate with perfusate viscosity (0.83, 1.02, 1.24 and 0.77 cP, respectively). NO-L-Ag and heparinase diminished dilatation by albumin, but not additively. Alone NO-L-Ag suppressed coronary flow during infusion of HES 450. Electron microscopy revealed a coronary EG of 300 nm, reduced to 20 nm after heparinase. Cultured endothelial cells possessed an EG of 20 nm to begin with. Conclusions: Albumin induces greater endothelial shear stress than HES, despite lower viscosity, provided the EG contains negative groups. HES 450 causes some NO-mediated dilatation via even a rudimentary EG. Cultured endothelial cells express only a rudimentary glycocalyx, limiting their usefulness as a model system.

The endothelial glycocalyx: a review of the vascular barrier

“…Increased endothelial shear increases nitric oxide (NO) production, which in turn dilates vessels and reduces stress [18]. Human umbilical vein endothelial cells stressed by shear double the amount of hyaluronic acid in the glycocalyx -a second mechanism through which shear could be controlled [9].…”

“…Albumin attenuated glycocalyx shedding during 4 h of cold ischaemia and reperfusion in guinea pig hearts, reducing interstitial oedema and intracoronary adhesion of leucocytes [40]. Albumin dilates coronary arteries compared with HES, possibly by enhancing NO production in response to shear stress: vasodilation by albumin was reduced when NO synthase was blocked and when the glycocalyx was damaged [18]. Fresh frozen plasma reduces glycocalyx damage and facilitated its restoration in rodent haemorrhagic shock [41].…”

Study on the Sliding Friction of Endothelial Cells Cultured on Hydrogel and the Role of Glycocalyx on Friction Reduction

“…Recent studies have found glycocalyx deficiency when the ECs are cultured in vitro [50,51]. Damiano E R. et al showed that the glycocalyx thickness of in vitro cultured human umbilical vein was 0.03 m under standard cell culture conditions, c.a.…”

Volume Management and Resuscitation in Thoracic Surgery

“…These are normally hidden deep within the glycocalyx structure, but become exposed following damage to the EGL [36 • ]. It also protects the vascular endothelium from shear stress and oxidative damage, via nitric oxideinduced vasodilation [37] and scavenging of oxygen free radicles [35].…”