[Effects of different patterns of hypoxia on renin angiotension system in serum and tissues of rats]

To Investigate the influences of chronic intermittent hypoxia (CIH) and continuous hypoxia (CH) on renin angiotensin system (RAS) in serum and tissues of rats, and therefore to investigate the mechanism of CIH-induced hypertension and hypoxia induced pulmonary hypertension.

Eighteen male Sprague-Dawley (SD) rats were divided into 3 groups: CIH group, CH group and control group (UC). CIH rats were subjected to alternating cycles of hypoxia (6% ∼ 8% O(2) in N(2) for 20 ∼ 25 s) and normoxia (21% O(2) in N(2) for 2 min) every 180 s for 7 h/d. CH rats were consistently given nitrogen (oxygen concentration 8% - 12% in the cabin, 7 h/d), while the UC rats were not treated.

Systolic blood pressure (SBP) in the CIH rats at the end of 6th week was significantly elevated compared with baseline SBP (P < 0.001), and that in the CH and the UC rats (P < 0.05). At the end of 6th week, the expression of ACE and ACE2 in the renal arteriole was significantly different (P < 0.05), and the levels of AngII in serum and kidney tissues were increased. Ang-(1-7) was decreased in the CIH rats compared with the CH and the UC rats (P < 0.05). The levels of AngII in pulmonary tissues were increased, while the levels of Ang-(1-7) were decreased in the CH rats compared with the CIH and the UC rats (P < 0.05). SBP showed a positive correlation with AngII in serum and kidney tissues, and a negative correlation with Ang-(1-7) in serum and kidney tissues. There were significant differences in arterial wall thickness, WT%, and WA% of renal arterioles and pulmonary arterioles among the 3 groups. Wall thickness of pulmonary arterioles and kidney arterioles was positively correlated with AngII in pulmonary and kidney tissues (r = 0.386, 0.414, P < 0.05), and negatively correlated with Ang-(1-7) (r = -0.401, -0.394, P < 0.05).

CIH and CH showed different effects on RAS in the serum and the tissues of rats. CIH mainly affected levels of RAS in the serum, kidney tissues and renal arterioles, and was closely related with blood pressure. CH mainly affected the levels of RAS in lung tissues and pulmonary small arteries, which may be related with pulmonary, hypertension and pulmonary arterial remodeling.