An immunoelectron microscopic study of von Willebrand factor in the thoracic duct endothelium of rats.

The localization of Von Willebrand factor-like immunoreactivity (VWFI) in the thoracic duct endothelium was investigated by means of preembedding immunoelectron microscopy. In the endothelial cells, VWFI was observed within rod-shaped Weibel-Palade bodies (WPBs) with an occasional tadpole-like appearance. The WPBs occasionally appeared to be associated with Golgi complexes of the endothelial cells. Some cisternae of the rough endoplasmic reticulum located in the perikarya of the endothelial cells also exhibited VWFI. There was a small number of large VWFI vesicles in the periphery of the endothelial cells. These findings provide morphological evidence for the thoracic duct as a site of VWF synthesis and suggest further that VWF is produced in the rough endoplasmic reticulum and transported into the WPBs and large vesicles occasionally via the Golgi apparatus.