OBJECTIVETo investigate the effects of estrogen on the activity and subunits expression of cytochrome c oxidase (COX) in mitochondria from genioglossus of chronic intermittent hypoxia (CIH) rat.

METHODSForty-eight male Sprague-Dawley (SD) rats were randomly divided into three groups: the normal control group (NC), the chronic intermittent hypoxia group (CIH) and estrogen plus hypoxia group (E + CIH). Rats in the latter two groups were used to build CIH models (8 h/d, 5 w). In the mean time, rats in NC group and CIH group were injected with sterile olive oil (0.2 ml each time, twice a week), and rats in E + CIH group were injected with estrogen (0.2 mg/kg, twice a week), respectively. At the end of the treatment, the genioglossus of the rat was removed and the mitochondria were isolated by centrifugation program. COX activity was measured with a spectrophotometer. The protein content of COX subunit I and IV was detected by Western blotting analysis, and mRNA expression levels of COXI and COXIV were determined by real-time polymerase chain action.

RESULTSCOX activity in CIH group [(0.143 +/- 0.029) microkat/mg] was lower significantly than that in NC group [(0.273 +/- 0.058) microkat/mg, P < 0.01]; In E + CIH group [(0.203 +/- 0.073) microkat/mg], COX activity was higher than that in CIH group (P < 0.05), but still lower than that in NC group (P < 0.05). Compared with NC group (47.325 +/- 7.502), decreased COXI expression was observed in CIH group (10.789 +/- 8.144, P < 0.01) and E + CIH group (25.593 +/- 11.108, P < 0.01). While in the mean time, the protein content of COXI in E + CIH group was higher than that in CIH group (P < 0.05). There was no significant difference in protein content of COXIV among the three groups (P > 0.05). COXI and COXIV mRNA levels had no significant change among the three groups (P > 0.05).

CONCLUSIONSCIH exposure could decrease mitochondrial COX protein expression and activity in the genioglossus of the rat, while estrogen administration might be beneficial to the recovery of those.