Membrane characteristics of cultured endothelial cells: identification of gap junction

Membrane characteristics of cultured endothelial cells derived from the superior vena cava of the rabbit were studied in freeze-fracture replicas. Gap junctions were identified, but tight junctions were not seen. In addition to pinocytic vesicles, fenestrations of plasma membrane which are not normally seen in the endothelium of vena cava in situ were found. This finding may be explained by the absence of platelets in the culture medium and is consistent with the current concept of endothelial-platelet interaction.