Cytoplasmic bodies in lymphatic endothelial cell.

Although micropinocytotic vesicles and other large vesicular structures have been observed in lymphatic endothelial cells on electron microscopy, in this study ultrastructure attention was focused on a variety of other membrane-bounded structures in the cytoplasm of these cells in the rabbit heart. The first type was oval or round in transverse section and elongated in longitudinal section, was 100-200 nm in diameter and contained regularly spaced tubules. These features resembled rod-shaped bodies detected thus far only in blood vascular endothelial cells. A second type of cytoplasmic body was also frequently seen in lymphatic endothelium. It contained irregularly spaced small vesicles, 5-7 in number and 45 nm in diameter. A third type of vesiculated body was only occasionally found. This latter structure was greater than the previously described bodies and ranged from 3-5 micron in diameter, and filled with granular, inhomogeneous material and filamentous-like components. The functional significance of these intraendothelial bodies is as yet unexplained.