模拟失重大鼠心肌细胞I_(Ca)对β-受体激动剂的反应性

Responsiveness of calcium currents to β-receptor agonist in cardiac myocytes of simulated weightless rats

目的 研究模拟失重大鼠心肌细胞钙电流 (ICa)对β-肾上腺素受体激动剂的反应性变化 .方法 用尾部悬吊大鼠模型模拟失重 (4 wk) ,胶原酶分离心肌细胞 ,用膜片钳全细胞方式记录单个心肌细胞的膜电容和 ICa等 .给予β-肾上腺素受体激动剂 (异丙肾上腺素 ) ,记录观察 ICa的反应性 .结果 对照组与悬吊组的 ICa密度无明显差别 (P>0 .0 5 ) ,ICa电流密度 -电压曲线基本一致 ;加入异丙肾上腺素后 ,两组 ICa密度均明显增大 ,但是两组的增加幅度不同 ,悬吊组的增加幅度 (84.3± 8.2 ) %明显小于对照组 (10 9.3± 7.9) % (P<0 .0 5 ) .结论 模拟失重 4wk大鼠心肌细胞的 ICa密度无明显改变 ;模拟失重后心肌细胞 ICa对

AIM To investigate the changes of responsiveness of calcium currents ( I Ca ) to β adrenergic receptor agonist in cardiac myocytes of simulated weightless rats. METHODS The rat tail suspension model was used to simulate weightlessness (4 wk). Cardiac myocytes were isolated with colla genase. Under whole cell recording mode of patch clamp technique, membrane capacitances and I Ca were recorded from the single ventricular myocytes. The responsiveness of I Ca was observed after stimulation by a β adrenergic receptor agonist (isoproterenol). RESULTS I Ca densities did not show significant difference between control and suspended groups ( P >0.05), and their I Ca density voltage curves were almost same. After isoproterenol was added, I Ca densities were obviously increased in both control and suspended groups, but their increase percentages were not equal. The increase percentage of I Ca density in suspended group (84.26±8.22)% was significantly less than that in control group (109.3± 9.9)% ( P <0.05). CONCLUSION It is suggested that I Ca densities of cardiac myocytes have no obvious changes in 4 wk simulated weightless rats. Responsiveness of I Ca to β adrenergic receptor agonist significantly decreases after simulated weightlessness.