Increased Sarcolemmal Permeability in the Cerebral Artery during Chronic Spasm: An Assessment Using DNA-Binding Dyes and Detection of Apoptosis

Abstract

Alteration of sarcolemmal permeability was evaluated in the cerebral artery after subarachnoid hemorrhage. Significance of membrane dysfunction in the pathogenesis of chronic spasm and contribution of apoptosis were investigated in a canine model. Permeability of the smooth muscle cell (SMC) membrane was assessed by double staining with a hydrophilic (ethidium bromide [EB]) and a lipophilic (Hoechst 33342) DNA-binding dye. Quantitative observations were made with a ultraviolet-fluorescence microscope and a ultraviolet-laser confocal microscope. Occurrence of apoptosis was studied using electrophoresis and TUNEL method. In the normal arteries, nuclei of SMC were stained with Hoechst 33342 but not with EB. In the spastic arteries, SMC in the inner layer of the tunica media were stained with EB. The incidence of EB-positive cells reached maximum on day 7 (45 ± 19%) and decreased in 2 to 4 weeks (13 ± 5.2% and 5.0 ± 2.1%, respectively), in parallel with amelioration of spasm. Electron and light microscopic observations revealed increased density of SMC cytoplasm with widening of the extracellular space. Necrosis was not evident. Apoptosis was not detected by the two methods. These results demonstrate that an augmentation in sarcolemmal permeability takes place during the course of chronic vasospasm and suggest its close correlation to pathogenesis.