A HYDROPHOBIC OLIGOLAMELLAR LINING TO THE VASCULAR LUMEN IN SOME ORGANS

Various endothelial surfaces from sheep and humans have been studied f or their hydrophobicity using a standard method based on the angle of contact (theta) of the surface with a droplet of saline placed on it. Most surfaces were relatively hydrophilic (theta < 25-degrees) but som e were distinctly hydrophobic with theta exceeding 65-degrees for shee p pulmonary vein, left ventricle, and aorta, and human umbilical vein. These results are discussed as compatible with the theory that surfac e-active phospholipid (surfactant) migrates from lung tissue into the pulmonary circulation or reaches intravascular sites from other source s. Transmission electron microscopy of cerebral vessels demonstrated a n oligolamellar lining of surfactant on many endothelial surfaces, bri dging the "tight" junctions between endothelial cells in many cases. L amellar bodies were found adjacent to the endothelium. The oligolamell ar surfactant lining and lamellar bodies are discussed as potentially very important factors in influencing bubble formation on vessel walls . It is believed to impart hydrophobicity while it could also determin e the microgeometry of any crevices vital for bubble formation or rete ntion.