长期吸入笑气对大鼠心肌功能的影响

Effect of long-term nitrous oxide inhalation on the cardiac function in rats

目的观察长期吸入笑气(N2O)是否会引起大鼠心肌功能的变化。方法将SD大鼠随机分为4组:空气吸入对照组(A组),500 mL/L N2O-15 d吸入组,2 h/d(B组),500 mL/L N2O-30 d吸入组,2 h/d(C组),500 mL/L N2O-50 d吸入组,2 h/d(D组)。用悬浮玻璃微电极记录离体心肌细胞的动作电位(APs),观测上述4组大鼠离体左心室肌细胞APs时程(MAPD90、MAPD50、MAPD20)和幅值的变化;用免疫组织化学方法检测心肌细胞的一氧化氮合成酶(eNOS)及血管紧张素-2(Ang-2)表达量的变化。结果①与A组相比,B组大鼠心肌细胞的MAPD无明显变化,C、D组MADP显著延长,差异具有统计学意义(P<0.05),但4组的APs幅值差异无统计学意义;②与A组相比,B组心肌细胞的Ang-2表达量无明显变化,C、D组Ang-2表达量显著增加;③与A组相比,C、D两组心肌细胞的eNOS表达量均明显减少(P<0.05)。结论长期吸入笑气可引起大鼠心肌电活动明显变化,其很可能与交感神经长时间过度兴奋致使Ang-2的表达增加有关。

Objective To observe whether or not long-term inhalation of nitrous oxide can affect the cardiac function in rats. Methods Sprague-Dawley rats of either sex were randomly divided into four groups. Group A： inhaled common air for 50 days as control; Group B： inhaled 500 mL/L N2O for 15 days, two hours every day; Group C： inhaled 500 mL/L N2O for 30 days, two hours every day; Group D： inhaled 500 mL/L N2O for 50 days, two hours every day. Float glass intracellular microelectrode recording technique was used for observation of the duration （MAPD90, MAPD50 and MAPD20 ） and amplitude of action potentials （APs） of left ventricular muscle cells in vitro. Angiotensin-2 （Ang-2） and eNOS were detected by immunohistochemical technique. Results （1） Compared with that in Group A, the Aps duration of left ventricular muscle ceils （MAPD） in Group B had no significant change while the MAPDs in Group C and Group D were extended significantly. There were no significant differences among the four groups in Aps amplitude. （2） The expression of Ang-2 did not differ significantly between Group B and Group A. The expression level was higher in Group C and D than in Group A. （3） The expression level of eNOS was significantly lower in Group C and D than in Group A （P〈0.05）. Conclusion Long-term inhalation of N2O can significantly affect the cardiac function in rats, which may be related to higher expression of Ang Ⅱ in the heart induced by the long-time excitation of sympathetic nerves.