[A study of the related pathways of oxidative stress in chronic intermittent hypoxia rats and the effect of N-acetylcysteine].

OBJECTIVE

To study the relation of oxidative stress with systolic blood pressure (SBP) and renin-agiotensin system (RAS) in a rat model of chronic intermittent hypoxia (CIH), and to investigate the preventive effect and mechanism of N-acetylcysteine (NAC) in CIH-induced hypertension.

METHODS

Twenty-four male Sprague-Dawley (SD) rats were divided into 4 groups: CIH+NAC group (CIH1), CIH+normal saline (NS) group (CIH2), CIH control group (CIH3) and blank control group (UC). CIH rats were subjected to alternating cycles of hypoxia (6%-8% O2 in N2 for 20-25 s) and normoxia (21% O2 in N2 for 2 min) every 180 s for 7 h per day. Rats in the CIH1 group were treated with NAC (800 ml×kg(-1)×d(-1)) by intraperitoneal injection, and those in the CIH2 group were treated with NS (5 ml×kg(-1)×d(-1)).

RESULTS

SBP in the CIH2 and CIH3 groups at the end of 6th week was significantly elevated compared with the baseline SBP (P<0.001) and those in the CIH1 and the UC groups (P<0.05). The expression of angiotensin-converting enzyme (ACE) and ACE2 in renal arterioles was significantly different (P<0.05), and the levels of angiotensin II (AngII) in the serum and kidney tissues, oxidation of low density lipoprotein (ox-LDL) and malondialdehyde (MDA) in the serum were increased. Ang-(1-7) and the inhibitory capability for hydroxyl free radicals in the serum were decreased significantly in CIH2 and CIH3 groups compared with CIH1 and UC (P<0.05) groups at the end of 6th week. SBP showed a positive correlation with AngII in serum and kidney tissues, but showed a negative correlation with Ang-(1-7) in serum and kidney tissues. The levels of MDS and ox-LDL in serum showed a positive correlation with AngII in serum and kidney tissues respectively, but showed a negative correlation with Ang-(1-7) in serum and kidney tissues respectively. The inhibitory capability for hydroxyl free radicals in serum showed a positive correlation with Ang-(1-7), but a negative correlation with AngII. The level of ox-LDL showed a positive correlation with MDA, but a negative correlation with the inhibitory capability for hydroxyl free radicals. There were no significant difference between CIH1 and UC groups in parameters except of SBP and AngII (P<0.05). All the data were not different between CIH2 and CIH3 groups (P>0.05).

CONCLUSIONS

CIH caused oxidative stress and RAS imbalance in rats. The imbalance of RAS in CIH rats was related with oxidative stress. The imbalance of RAS and oxidative stress may be one of the important mechanisms for CIH-induced hypertension. NAC can prevent CIH-induced hypertension through modulation of RAS by its anti-oxidative effect.