The possible role of endothelium in prevention of rebleeding in experimental subarachnoid hemorrhage (SAH).

Experiments were performed on six male cats under nitrous oxide in oxygen anesthesia. Animals were paralysed and artificially ventilated. Subarachnoid hemorrhage (SAH) was produced by basilar artery puncture following clivectomy. After 10 minutes (3 cats) and 60 minutes (3 cats) the basilar artery was dissected and fixed for electronmicroscopic examination. Ultrastructural examinations revealed in the cytoplasm of the endothelial cells on the side of the vessel lumen, the presence of spherical or flattened cylindrical structures identified as Weibel-Palade bodies. In the endothelium of the proximal segment, 10 and 60 minutes after puncture, the number of these electron-dense bodies increased, and was higher than in the corresponding distal segment. The possible role of the Weibel-Palade bodies in SAH after-effects is discussed.