[A study on rat cardiovascular injury induced by intermittent hypoxia and the protective role of adiponectin]

To observe the effect of chronic intermittent hypoxia (CIH) on rat cardiac function and blood pressure, and the protective role of adiponectin (Ad).

A total of 24 male Wistar rats were randomly and equally divided into 3 groups: normal control group (NC group), chronic intermittent hypoxygen group (CIH group) and CIH+Ad group. Normal air breathing for NC group and CHI for CIH and CIH+Ad groups were conducted for 28 days. In addition, rats in CIH+Ad group were given intravenous adiponectin at a dosage of 20 µg each time, once a week for successive 4 weeks. The results of echocardiography, blood pressure, plasma adiponectin, endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) were compared among the three groups after 28 days.

HE stain showed that the myocardial cells of CIH rats were damaged by CIH. Compared with NC group, rats in CIH group presented with a greater heart/body weight ratio (0.070 ± 0.008 vs. 0.057 ± 0.009, P < 0.05) and systolic blood pressure [(132 ± 4) vs. (123 ± 6) mmHg(1 mmHg = 0.133 kPa), P < 0.05] and a lower LVEF [(70.3 ± 4.1)% vs. (84.1 ± 2.5)%, P < 0.05]. Plasma ET-1 was increased while NO(-)(2)/NO(-)(3) and eNOS decreased in CIH group, compared with NC group [(26.2 ± 6.9) ng/L vs. (7.7 ± 2.7) ng/L, (37 ± 9) µmol/L vs. (65 ± 10) µmol/L, (18 ± 5)µg/L vs. (27 ± 6) µg/L, respectively; P < 0.05]. The heart/body weight ratio, blood pressure and LVEF were improved in CIH+Ad group compared with those in CIH group [0.064 ± 0.009 vs. 0.070 ± 0.008, (127 ± 6) mmHg vs. (132 ± 4) mmHg, P > 0.05; (79 ± 7)% vs. (70 ± 4)%, P < 0.05; respectively]. Plasma ET-1 levels in CIH+Ad and CIH groups showed no significant difference, but were significantly lower in NC group. However, rats in CIH+Ad group had a higher NO(-)(2)/NO(-)(3) level than that in CIH group. Bivariate Correlations showed that NO(-)(2)/NO(-)(3) and eNOS were negatively correlated with systolic blood pressure while heart/body weight ratio, LVEDs, ET-1 and NO(-)(2)/NO(-)(3) were negatively correlated with left ventricular ejection fraction.

Through xidative stress, ET-1 and NO imbalance and impaired vascular endothelial function, cardiac function could be damaged by CIH in rats, while supplement of extrinsic adiponectin could improve these damages.