REDUCTION OF INTRACELLULAR GLUTATHIONE LEVELS PRODUCES SUSTAINED ARTERIAL NARROWING

OBJECTIVE: Although lipid peroxidation and alterations in endogenous a ntioxidants have been hypothesized to contribute to cerebral vasospasm after subarachnoid hemorrhage, there has been no direct evidence demo nstrating the relationship between oxidative stress and delayed arteri al narrowing. To elaborate the role of the endogenous intracellular an tioxidant and electron exchanger glutathione (GSH) in cerebral vasospa sm, rat femoral arteries were treated with perivascular application of L-buthionine-(SR)sulfoximine (BSO), which inhibits the synthesis of G SH. METHODS: To determine the dose-response relationship, BSO at doses of 10 to 100 mg/ml, in platelet-rich plasma, was applied for 7 days t o rat femoral arteries in vivo. Vessels were then perfusion-fixed for morphometric analysis of luminal cross-sectional area. To determine th e time course of arterial narrowing, BSO (75 mg/ml) was applied to fem oral arteries for 1, 3, 7, or 21 days before histological analysis, as described above. With rats treated with 50 to 100 mg/ml BSO, exogenou s GSH (100 mg/kg) was administered, by intraperitoneal injection, dail y for 7 days. To demonstrate the mechanism of BSO effects in smooth mu scle cells (SMCs), cultured rat aortic SMCs were treated with 1 mmol/L BSO for 24 hours and assayed for intracellular levels of GSH and two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal. RESULTS: Compared with control arteries treated with platelet-rich pla sma alone, perivascularly administered BSO applied for periods of 1 to 21 days produced sustained and reversible narrowing of rat femoral ar teries with a time course, severity, and histological appearance analo gous to those observed after perivascular application of whole blood. BSO-induced arterial narrowing was dose-dependent, with 60% reductions in the luminal cross-sectional area being noted at 75 and 100 mg/ml ( P < 0.005). Systemic administration of exogenous GSH slightly inhibite d the effect of BSO on arterial narrowing, although the inhibition was not statistically significant. Cultured rat aortic SMCs exposed to BS O for 24 hours showed a 70% decrease in intracellular GSH levels (P = 0.03); levels of two products of lipid peroxidation, malondialdehyde a nd 4-hydroxyalkenal, were increased by 25% (P = 0.24) and 38% (P = 0.0 9), respectively. CONCLUSION: These data support the hypothesis that d iminished intracellular levels of GSH may produce delayed chronic arte rial narrowing after subarachnoid hemorrhage. The specific mechanism b y which GSH levels modulate vasoconstriction remains uncertain but may involve endogenous antioxidant capacity in SMCs.