Non-aqueous fixative preserves macromolecules on the endothelial cell surface: an in situ study

A fixative composed of 1% w/v osmium tetroxide dissolved in a fluorocarbon (FC-72) was used to perfusion-fix rat blood vessels for this ultrastructural study. With non-aqueous fixation, the lumenal surfaces of endothelial cells in cardiac and skeletal muscles retained an extracellular coat which was morphologically consistent with glycocalyx. Venules displayed the greatest density and depth (up to 870 nm thick) of glycocalyx, but all vessel types had at least 70 nm of surface coat. The results indicate that non-aqueous fixatives will be useful in studies of the endothelial cell lumenal surface, while offering excellent preservation of general ultrastructure.