HEMOGLOBIN PENETRATION IN THE WALL OF THE RABBIT BASILAR ARTERY AFTERSUBARACHNOID HEMORRHAGE AND INTRACISTERNAL HEMOGLOBIN INJECTION

The ability of hemoglobin (Hb) to penetrate the basilar arterial wall in vivo after experimental subarachnoid hemorrhage was examined using immunohistochemistry. The distribution of anti-Hb antibodies in rabbit basilar artery was studied following the injection of autologous bloo d in the cisterna magna. Vessels removed two or four days after subara chnoid hemorrhage exhibited varying degrees of vasospasm, and exhibite d Hb immuno-fluorescence throughout the vessel wall. Hemoglobin immuno fluorescence was most conspicuous in the adventitia but was also seen in the smooth muscle and endothelial cell layers in 7 of 10 animals. T he degree of vasoconstriction correlated with the total amount of Hb-f luorescence present in the vessel wall. When Hb solution alone was inj ected into the subarachnoid space, vasoconstriction was evident but pe netration into the vascular layers was not as extensive as that observ ed after injection of autologous blood. These findings demonstrate tha t Hb is able to penetrate through the arterial wall after subarachnoid hemorrhage. The results provide direct support for the hypothesis tha t Hb-induced changes in smooth muscle and/or endothelial function can contribute to the pathogenesis of vasospasm.