Objective: To observe the effects of two different hypoxia patterns on blood pressure and the underlying mechanisms.
Methods: Eighteen male SD rats were randomly divided into three groups: the intermittent hypoxia group (IH group), the continuous hypoxia group (CH group) and the normal control group (NC group). The rats of the IH and CH group were subjected to intermittent hypoxia (7 h/d) and continuous hypoxia (7 h/d) for 42 days respectively. The NC group rats were untreated. The levels of arteria caudilis systolic pressure (ACSP) were measured with noninvasive rats arteria caudilis gauge before the experiment, at the end of 3rd, 6th week of the experiment. The concentrations of norepinephrine (NE) in serum and neuropeptide Y (NPY) in plasma were respectively measured by enzyme-linked-immunosorbent assay (ELISA) and radioimmunoassay. The contents of malondialdehyde (MDA) and the ability of inhibiting hydroxyl free radical in serum were analyzed by thiobarbituric acid colorimetric analysis (TBAR) at the end of 6th week.
Results: At the end of 3rd week, the levels of ACSP were considerably higher than those before the treatment (P<0.05). The concentrations of ACSP, NE, MDA, NPY in the IH group were significantly higher than those in the other two groups at the end of 6th week (all P<0.01). The ability of inhibiting hydroxyl free radical were decreased by the intermittent hypoxia treatment (all P<0.01). However, there was no significant difference in ACSP, NE, MDA, NPY between CH and NC group (all P>0.05). The levels of NE, NPY and MDA were positively related with ACSP (r=0.873, P<0.01; r=0.671, P<0.01; r=0.582, P<0.05). The correlation between the ability of inhibiting hydroxyl free radical and ACSP was negative (r=-0.790, P<0.01). the concentrations of MDA were positively related with NE and NPY respectively (r=0.843, 0.777, P<0.01) and the ability of inhibiting hydroxyl free radical was negatively related with NE and NPY respectively (r=-0.864, -0.717, P<0.01).
Conclusion: Intermittent hypoxia can induce high blood pressure, which may be related to the sympathetic over-activity and the oxidative stress.