Endothelial Transcytosis Research Articles

Barrier disruption in the major cerebral arteries during the acute stage after experimental subarachnoid hemorrhage.

The effects of experimental subarachnoid hemorrhage (SAH) on the blood-arterial wall barrier in the basilar arteries were studied during the acute stage after SAH. SAH was induced in rats by injecting fresh autologous blood into the cisterna magna. Horseradish peroxidase (HRP) was given intravenously before killing the animals to assess the integrity of the barrier. In the basilar arteries taken from the animals that were killed 30 minutes after the cisternal injection of either mock cerebrospinal fluid or arterial blood, HRP reaction products were diffusely observed in the subendothelial spaces and smooth muscle layers. At 5 hours after the blood injection, no permeation of HRP into the subendothelial space was observed. Endothelial cell transcytosis seemed to be the important mechanism for HRP permeation into the subendothelial space rather than the opening of interendothelial junctions. The disruption of the blood-arterial wall barrier in the major cerebral arteries after SAH may be involved in the pathogenesis of vasospasm.

Endocytosis and exocytosis of protein in capillary endothelium.

The transport of proteins across continuous capillary endothelium is believed to be mediated by micropinocytic vesicles which shuttle molecules between the lumenal and abluminal plasma membrane. We have studied the ability of capillary endothelial cells isolated from rat epididymal fat to endocytose fluorescently labelled ovalbumin within micropinocytic vesicles. Net association of fluorescent ovalbumin with endothelial cells reaches an equilibrium after 40 minutes of incubation. This equilibrium is presumably due to a balance between endocytosis and subsequent exocytosis of this protein. Capillaries equilibrated with fluorescent ovalbumin exhibited rapid exocytosis of this protein when it was removed from the external medium. The rate of endocytosis was concentration dependent and obeyed the kinetics expected for adsorptive phase endocytosis. High concentrations of ovalbumin stimulated the ingestion of 14C-sucrose, a marker of fluid endocytosis, suggesting that protein can affect the movement of vesicles within the endothelial cytoplasm. These results imply that capillary endothelium isolated from rat epididymal fat exhibits the ability to endocytose and subsequently exocytose protein. This demonstrates that the two components of endothelial vesicular transport or transcytosis can be observed and studied in a system of isolated capillary endothelium.