Alterations of Insulin-like Growth Factor-I mRNA and IGF Binding Protein-5 mRNA Expression Following Hypoxic-Ischemic Brain Injury in Immature Rat

Lee, Kee Hyoung; Lim, Ji Hye; Choi, Byoung Min; Eun, Baik Lin

Abstract

PURPOSE
Insulin-like growth factor-I(IGF-I) is an essential anabolic factor for postnatal rat brain development and IGF-I expression is highly abundant during the first 21 days, critical growth period. Hypoxic-ischemic brain insults occurring during the perinatal period result in neuronal necrosis and permanent brain damage. To investigate the regulation of the action of IGF-I in response to such a hypoxic insult, we examined the gene expression of IGF-I and IGFBP-5 during the first 72 hr after hypoxic-ischemic injury in immature rat brain.
METHODS
Ligation of the right carotid artery of 7-day-old rats was followed by 2 hour exposure to 8% oxygen to produce severe hypoxic brain damage. Using reverse transcriptase-polymerase chain reaction(RT-PCR), the expression of IGF-I mRNA and IGFBP-5 mRNA was determined in both hypoxic and control brains at post 1, 4, 12, 24, 48 hr and 72 hr after hypoxic-ischemic insult.
RESULTS
The IGF-I mRNA and IGFBP-5 mRNA expression of hypoxic brain were not different from those of controls at 1 hr of recovery but IGF-I mRNA expression was decreased rapidly at post 4 hr, this decrease more pronounced at 12 hr of recovery. IGF-I mRNA and IGFBP-5 mRNA expression were increased at 48 hr and 24 hr of recovery, respectively and both IGF-I mRNA and IGFBP-5 mRNA expression showed similar level of controls at 72 hr of recovery.
CONCLUSION
Out findings suggest that IGF-I play a important role in both neuronal loss and repair process following hypoxic-ischemic brain injury and IGFBP-5 is also strongly involved in the repair of damaged brain tissue by mediating IGF-I action. (J Korean Soc Pediatr Endocrinol 2003;8:56-63)