Apoptosis and Expression of Nitric Oxide Synthase in Hypoxic Ischemic Cerebral Injury of Rats / 대한소아신경학회지

ABSTRACT

PURPOSE: Recently, it was reported that apoptosis in hypoxic ischemic cerebral injury is involved in neuronal injury while nitric oxide synthase(NOS) is involved in neuronal apoptosis. The aim of the present study is to investigate the relationship between the expression pattern of NOS and the apoptosis in hypoxic ischemic cerebral injury of rats. METHODS: To investigate the expression pattern of nitric oxide synthase and the relationship between apoptosis and activity of NOS, immunoelectron microscopic examination and in situ apoptosis detection(TUNEL) were performed in male Sprague Dawley rats. Ischemic injury was induced by permanent ligation of left common carotid artery and hypoxic injury by exposure of a mixture of 10% oxygen+90% nitrogen gas. Unicryl embedding method was used for immunoelectron microscopy and Apoptag kit for apoptosis. RESULTS: The number of apoptotic cells reached the highest at 24 hr, decreased after 72 hr and maintained the expression level until 168 hr. nNOS was expressed in neurons of the cortex, peaked at 24 hr and decreased after 72 hr. However, nNOS was not detected in the hippocampus. eNOS was expressed at 12 hr and at 24 hr in the hippocampus and the cortex, respectively, and persisted at each time point. iNOS was expressed after 72 hr in the cerebral cortex and the hippocampus. CONCLUSION: The expression of three isoforms of NOS in hypoxic ischemic cerebral injury was different in time. nNOS seems to be involved in cortical damage in the early phase of hypoxic ischemic cerebral injury and iNOS is related to apoptotic cell deaths in the late phase, but further study on their mechanisms will be needed.