Effects of perfusate composition on binding of ruthenium red and gold colloid to glycocalyx of rabbit aortic endothelium.

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.