Induction of the Expression of Heme Oxygenase Gene in PC12 Cells by Hypoxia

Summary: To investigate the expression of the HO-1 gene in PC12 cells in hypoxic environmentand gain further insight to the role of HO-1 in cerebral ischemia, PC12 cells were exposed to hy-poxia environment (95 % N2,5 % CO2) for 0. 5 h, 1 h, 4 h, 8 h, 12 h, 24 h respectively. Thelevel of HO-1 mRNA was examined by reverse transcriptase polymerase chain reaction (RT-PCR); the volume of COHb in the media were measured spectrophotometrically and the cGMPconcentration of PC12 cell extracts was determined by radioimmunoassay. We found that after ex-posure to hypoxia for 1 h, 4 h, 8 h, 12 h, 24 h, HO-1 mRNA increased by 3 %, 4 %, 17 %, 31%, 36 % as compared with that in control group respectively (P＜0. 01 or P＜0. 05) ; the COHbincreased by 12 %, 29 %, 59 %, 88 %, 94 % as compared with that in control group respectively(P＜0. 01 or P＜0. 05), and the cGMP concentration were 2. 2, 3. 4, 5.2, 8. 1, 10. 9-fold as thatof the control group (P＜0. 01). We are led to conclude that hypoxia induced the expression ofHO-1 gene, the production of endogenous CO, and the concentration of cGMP was elevated aswell.