Abstract
The effects of perfusate composition on some of the properties of the endothelial glycocalyx were investigated electron microscopically. Rabbit aorta was perfused in situ in preparation for fixation with 1% OsO4 containing 0.1 Ruthenium red (RR) or perfusion with wheat germ agglutinate (WGA)-coated gold particles suspended in 0.9% NaCl, Tyrode's solution, or pooled rabbit serum. Intense RR staining of the intimal glycocalyx was found only in vessels that had been exposed to 150 mmol/L NaCl, pH 7.4, or to albumin (4.0 g/100 ml), gamma-globulin (0.7 g/100 ml), or fibrinogen (0.3 g/100 ml) in Tyrode's solution, pH 7.4, for 5 min prior to fixation. The adherence of WGA-coated gold particles to the intimal and vasa vasorum glycocalyces was found in saline- and Tyrode's-perfused vessels. The density of the WGA-coated gold particles was greatest in the glycocalyx of damaged endothelium. In vessels flushed with serum, no RR stain or WGA-coated gold colloid was seen in the glycocalyx. This study demonstrates that saline perfusion facilitates the passage of RR and WGA-coated gold particles into the endothelial glycocalyx. We conclude that serum proteins and cell-surface glycoprotein chains act cooperatively to impede the access of some molecules to the endothelial surface.