Distribution of cell surface charges on mesothelium and lymphatic endothelium.

The distribution of anionic sites on the luminal surfaces of the peritoneal mesothelium and lymphatic endothelium was investigated by injecting cationized ferritin (CF) intraperitoneally. After washing with phosphate-buffered saline, the diaphragm was fixed and processed for electron microscopy. CF label occurred in discontinuous patches along the mesothelial surface. Microvilli were heavily marked and often closely applied to the mesothelial surface. The intercellular cleft was also heavily labeled. The luminal aspect of the lymphatic endothelium was more extensively labeled, with the marker occurring in long discontinuous dense bands. The clefts of lymphatic endothelial intercellular junctions were extensively labeled especially along regions where cells were loosely apposed. The existence of a high density of anionic sites on membranes at the intercellular junctions of both mesothelial and lymphatic endothelial cells represent a salient feature which is very different from binding in blood capillary endothelium. The presence of a high density of anionic sites along the intercellular clefts of adjacent cells may play a role in the rapid movement of small solutes and molecules from interstitial spaces into the lymphatic lumen.