Cellular heterogeneity of rat vascular endothelium as detected by HPA and GS I lectin-gold probes

BACKGROUND: In order to extend previous observations on the heterogeneity in labeling of rat vascular endothelium by the lectins GS I and LEA [1,2], we have conducted a survey of several organs with a lectin panel with greater variety of carbohydrate specificity. MATERIAL AND METHODS: Submandibular gland, duodenum, distal colon, liver, kidney, heart, skeletal muscle, adrenal gland, ovary, cerebral and cerebellar cortex of a rat have been examined by light and electron microscopy using lectin-gold probes on Lowicryl K4M embedded tissue. RESULTS: Five lectins (LCA, con A, LEA, RCA, WGA) labeled vascular endothelial cells in the connective tissue of all the organs studied, while PNA, EEA, TPA, LABA, UEA I expressed no detectable affinity towards endothelial cells. HPA and GS I reacted with most endothelial cells, except those in the kidney glomeruli, liver sinusoids and zona fasciculata of adrenal gland. In cerebral and cerebellar cortex GS I reacted witn pericytes of large vessels, but not with endothelial cells of the capillary bed. SDS-PAGE extracts of heart, skeletal muscle and cerebral cortex reveal that differences in GS I labeling depend, at least in part, on 40 and 200 kD glycoproteins, present in heart and skeletal muscle, but not cerebral cortex. CONCLUSIONS: Data indicate, that GS I, widely used for selective histochemical labeling of rat endothelial cells is not uniform endothelial marker in all organs. More precise investigation of these lectin reactive determinants in rat vascular endothelium, including developmental changes, isolation and enzyme-FACE sequencing of their carbohydrate moieties, generation of antibodies and their possible organ specific binding affinities could give new insight into the physiological role of GS I and HPA binding glycoproteins in rat endothelium.