Increased sarcolemmal permeability in the cerebral artery during chronic spasm: An assessment using DNA-binding dyes and detection of apoptosis

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 investiga ted in a canine model. Permeability of the smooth muscle cell (SMC) membran e was assessed by double staining with a hydrophilic (ethidium bromide [EB] ) and a lipophilic (Hoechst 33342) DNA-binding dye. Quantitative observatio ns were made with a ultraviolet-fluorescence microscope and a ultraviolet-l aser confocal microscope. Occurrence of apoptosis was studied using electro phoresis and TUNEL method. In the normal arteries, nuclei of SMC were stain ed 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-p ositive 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 ameli oration of spasm. Electron and light microscopic observations revealed incr eased density of SMC cytoplasm with widening of the extracellular space. Ne crosis was not evident. Apoptosis was not detected by the two methods. Thes e results demonstrate that an augmentation in sarcolemmal permeability take s place during the course of chronic vasospasm and suggest its close correl ation to pathogenesis.