抄録
Oxyhemoglobin (oxyHb) is postulated as the most potent trigger of prolonged vasoconstriction after subarachnoid hemorrhage, while methemoglobin (metHb) is much less potent. It is unknown whether or not oxyHb may directly act upon the vessel wall in subarachnoid hemorrhage. OxyHb may be responsible for vasoconstriction not directly but indirectly through superoxide anion radical (O·-2) derived from auto-oxidation of oxyHb.
Generation of O·-2 and activity of superoxide dismutase (SOD) was studied in the incubated whole blood or washed erythrocyte of human artery under the condition simulated to subarachnoid hemorrhage.
Results indicated that generation of O·-2 and activity of SOD were preserved during incubation for 8 days at 37°C. The preserved SOD activity might indicate that O·-2 does not react directly upon the vessel wall to bring about vasoconstriction. It was suggested that other noxious free radicals or active oxygen dismutated from O·-2 might participate in prolonged vasoconstriction.
The phasic changes of oxyHb on the course of auto-oxidation was analyzed with electron spin resonance (ESR). The characteristic changes of ESR signals of ferric protein compound from high to low spin corresponded to the changes from oxyHb to superoxide nietlIb, metllb and hemichronie during the incubation period. These changes were observed in the cerebrospinal fluid from patients who suffered from prolonged vasospasm after subarachnoid hemorrhage.
Oxyllb may participate in prolonged vasoconstriction indirectly.
