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.