Regional disparity in the vascular response to subarachnoid hemorrhage--relationship between alteration of the concentration of eicosanoids and electron microscopic findings.

In an attempt to document the apparent regional disparity of the vascular response to subarachnoid hemorrhage (SAH), the authors measured the concentrations of eicosanoids in various arterial segments corresponding to alterations observed on electron microscopy, using cats with experimentally produced SAH. The level of thromboxane B2 was elevated in both the arterial walls and cerebral cortices, particularly in the latter, on day 7 after SAH production. The 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) levels in the SAH group were decreased in the basilar and pial arteries after the production of SAH. The mean concentration of 6-keto-PGF1 alpha in the cerebral cortices showed only slight, erratic changes. Ultrastructural observations revealed that the vessels of smaller diameter, such as the pial vessels, underwent more marked spastic changes than did those of larger diameter. These results suggest that the ischemic events following SAH may have been induced by vasospasm and increased coagulability caused by changes in the concentrations of arachidonic acid metabolites in arteries of relatively small diameter.