环孢酶素A对缺氧大鼠右心室心肌CaN活性及血浆NO、一氧化氮合酶、内皮素-1水平的影响

目的 通过研究钙调神经磷酸酶(CaN)抑制剂对缺氧大鼠右心室心肌CaN活性及血浆一氧化氮合酶(iNOS)、NO、内皮素-1(ET-1)水平的影响,探讨CaN在慢性缺氧性右心室心肌肥厚中的作用。方法 将大鼠置于氧浓度为(10.0±0.5)%的大型玻璃舱中,每天24 h缺氧,持续7 d,建立大鼠慢性缺氧模型。实验大鼠分3组,即正常组、缺氧组、环孢酶素(CsA)处理组,每组各8只。缺氧组持续缺氧14 d,处理组在缺氧的同时腹腔内注射CsA(20 mg/kg·d)。第14天处死大鼠,取血,测NO、ET-1、iNOS水平,分离心脏称质量,并留右心室测CaN活性水平。结果 (1)缺氧组右室与左室加室间隔的质量比、右室质量/体质量均明显高于正常组和CsA处理组(P<0.01)。(2)缺氧组右心室心肌CaN活性明显高于正常组(P<0.01),而CsA处理组则明显低于缺氧组(P<0.01)。(3)缺氧组血浆NO、iNOS水平明显低于正常组(P<0.01),ET-1水平则明显高于正常组(P<0.01);而CsA处理后血浆NO、iNOS水平明显高于缺氧组(P<0.01),ET-1水平则明显低于缺氧组(P<0.01),与正常组之间差别无统计学意义(P>0.05)。结论 CaN抑制剂CsA对心肌肥厚的抑制作用可能与抑制CaN活性,调节血NO、iNOS和ET-1水平,改善肺动脉压力等有关。

Effect of cyclosporine A on myocardial calcineurin activity of the right ventricle and plasma NO,nitric oxide synthase and endothelin-1 levels in rats with chronic hypoxia

Objective To study the role of calcineurin in the progression of right ventricle myocardial hypertrophy in rats exposed to chronic hypoxia by examining the effect of Ca²⁺ channel blockers on the activation of calcineurin and plasma levels of nitric oxide (NO), NO synthase, and endothelin-1 (ET-1). Methods Rat models of right ventricle myocardial hypertrophy were established by exposing the rats to chronic hypoxia in 10.0%±0.5% O₂ for 7 d. The 24 rat models were assigned into normoxic group, hypoxic group and cyclosporin A (CsA)-treated hypoxic group. The rats in normoxic group were kept under normoxic environment, while those in the other 2 groups were subjected to further hypoxic treatment for 14 d, with the rats in CsA group receiving intraperitoneal CsA injection at 20 mg/kg on a daily basis. On day 21 of the experiment, all the rats were killed to collect the hearts for measuring the weight ratio of the right ventricle to the left ventricle and interventricular septum RV/(LV+S)], as well as the right ventricle to body weight ratio (RV/BW); blood samples were also drawn from the ventricles for measuring plasma NO, iNOS, and ET-1 levels, with the ventricular myocardial Ca²⁺]_i and the activity of calcineurin also determined. Results The RV/(LV+S) and RV/BW were significantly higher in hypoxic group than those of the normoxic and CsA groups (P<0.01); the right ventricular myocardial Ca²⁺]_i in CsA group was significantly higher than that in the other two groups (P<0.01). In comparison with the normoxic group, the right ventricular myocardial calcineurin activity was significantly increased in the hypoxic group. CsA treatment significantly suppressed calcineurin activity (P<0.01). Conclusions Calcineurin possibly plays a role in the progression of right ventricle myocardial hypertrophy in rats with chronic hypoxia. Blocking L-type Ca²⁺ channels with CsA effectively prevents the development of myocardial hypertrophy possibly by inhibiting calcium influx and suppressing calcineurin activity.