Cell surface chemistry of arterial endothelium and blood monocytes in the normolipidemic rabbit.

Chemical mapping of the luminal surface of normal rabbit aortic and coronary endothelium was investigated cytochemically to establish a baseline for further comparison with the biochemical changes possibly induced by the experimental hypercholesterolemia. Morphometric analysis showed that in the aortic endothelium the plasma membrane exposes a large number of uniformly-distributed positively-charged groups of high pKa, and a heterogeneous pattern of dense anionic groups of low pKa. Among the latter, only a third was represented by neuraminidase-cleavable sialic acids. These are constituted by various classes of N-, and O-substituted sialyl residues in glycoconjugates, most frequent being those non-O-acetylated at C8 or C9. Among the oligosaccharides detected with lectins, very abundant were the glycoconjugates containing mannosyl and subterminal galactosyl, whereas N-acetyl-glucosamine, terminal galactosyl and N-acetyl-galactosaminyl moieties were rather poorly represented. The density of the latter two markedly increased after its unmasking by neuraminidase treatment. Coated pits contained both anionic and cationic sites, but only few sialic acids and saccharide residues in significantly lower amounts than plasma membrane. The membrane of plasmalemmal vesicles displayed a high number of cationic sites and mannosyl residues, but very few anionic groups, sialyl residues, and galactosyl and N-acetyl-galactosaminyl moieties. Coronary endothelium displayed a chemical pattern similar to aorta, with some differences, especially in the frequency of some oligosaccharides. Vena cava was low in acidic groups but rather rich in galactose. Plasmalemmal vesicles were only occasionally labeled by the probes used. Monocyte surface exhibited a high density of anionic sites, and binding sites for wheat germ agglutinin and Ricinus communis agglutinin. No mononuclear cells were observed adhering to endothelial surface.