Abstract:OBJECTIVE: To study the role of the changes of second messenger protein kinase C (PKC), inositol 1,4,5 trisphosphate (IP 3) and expression of immediately early gene c fos protein (c fos) in the pathogenesis of hypoxic ischemic encephalopathy (HIE) of neonatal rats. METHODS: Fifty seven 7 day old Wistar rats were put into a an air tight container with 5% O 2 and 95% nitrogen for 20 minutes after their right common carotid arteries were occluded, and then they were sacrificed at 0, 4, 12, 24, 48 and 72 h, and 7, 14 and 21 d after hypoxic ischemic (HI) insult. The rats experienced only pseudo operation were used as the controls. PKC activity was measured by the incorporation of [γ- 32 P] into a specific substrate peptide in the cytosolic and particulate fraction respectively. IP 3 was determined by the radioreceptor binding assay. C fos expression was detected by immunohistochemical method. RESULTS: Compared with the non HI controls, PKC activities in particulate fractions in both cerebral cortex and hippocampus decreased, whereas increased in cytosol in cerebral cortex and remained within the normal range in cytosol in hippocampus at 0, 4, 12, 24, 48 and 72 h, and 7 d after HI. The changes of PKC activities were obvious within 72 hs and lasted to 14 d after HI. A decrease of the IP 3 level in cerebral cortex and hippocampus and an increase of the IP 3 level in thalamus were noted after HI. The changes of the IP 3 level restored to normal on 14 d after HI. The expression of c fos was found in different parts of brain immediately after HI and peaked at 4 h, and thereafter, its density gradually decreased and lasted to 72 h. The expression of c fos was obvious in Ⅱ-Ⅴ layers of cortex, CA1 and DG of hippocampus respectively, and slightly increased in thalamus.CONCLUSIONS: HI could induced the changes of the second messengers PKC and IP 3. The continuous PKC down regulation and c fos gene expression may take part in neuron injuries during hypoxic ischemic brain injury.
