Capasso J M, Remily R M, Sonnenblick E H
Basic Res Cardiol. 1983 Sep-Oct;78(5):492-504. doi: 10.1007/BF01906460.
To investigate the possible role of an alteration in excitation-contraction coupling during development, aging and senescence we compared simultaneously recorded mechanical and electrical activity of left ventricular papillary muscles from 3, 6, 12, and 24-month-old male rats. In addition, the effects of calcium and verapamil on excitation-contraction coupling were evaluated. We recorded transmembrane action potentials during both isometric and isotonic contractions. At al external bath calcium = 2.4 mM, action potential duration at 75% complete repolarization (APD75) was significantly prolonged as a function of age (3 mo = 28.2 +/- 2.7; 6 mo = 29.5 +/- 2.6; 12 mo = 49.5 +/- 5.6; 24 mo = 121 +/- 8.5 msec) while peak developed tension (DT) was not significantly altered (3 mo = 5.13 +/- 0.53; 6 mo = 4.75 +/- 0.53; 12 mo = 7.26 +/- 0.51; 24 mo = 6.01 +/- 0.67 g/mm2). The correlation coefficient (r value) for APD75 and DT was strong for 3-month-old animals (4 = 0.99) but weakened as a function of age (6 mo = 0.93; 12 mo = 0.81; 24 mo = 0.57). Similar results were observed when APD75 was correlated with time-to-peak tension (TPT) (3 mo = 0.95; 6 mo = 0.98; 12 mo = 0.85; 24 mo = 0.68), time-to-one-half relaxation (T1/2R) 3 mo = 0.91; 6 mo = 0.97; 12 mo = 0.85; 24 mo = 0.81) and time to peak shortening (TPS) (3 mo = 0.89; 6 mo = 0.81; 12 mo = 0.82; 24 mo = 0.51). Correlations between action potential duration and contractile parameters became weak in all age groups upon the addition of verapamil (V). The correlation between APD75 and DT for 3-month-old animals decreased by 34% upon the addition of V while a 70% decrease was seen in 24-month-old animals. Similar results were seen when APD75 was correlated with TPT, T1/2R and TPS when V was added to the perfusate. Our results indicate that excitation-contraction coupling, as evidence by alterations in not only the contractile apparatus but also in the surface membrane, may be altered in ventricular muscle as in function of age.
为了研究兴奋 - 收缩偶联改变在发育、衰老过程中可能发挥的作用，我们比较了3、6、12和24月龄雄性大鼠左心室乳头肌同时记录的机械和电活动。此外，评估了钙和维拉帕米对兴奋 - 收缩偶联的影响。我们在等长和等张收缩过程中记录跨膜动作电位。在细胞外浴钙浓度为2.4 mM时，动作电位在75%复极化完成时的时程（APD75）随年龄显著延长（3月龄 = 28.2±2.7；6月龄 = 29.5±2.6；12月龄 = 49.5±5.6；24月龄 = 121±8.5毫秒），而最大张力（DT）无显著改变（3月龄 = 5.13±0.53；6月龄 = 4.75±0.53；12月龄 = 7.26±0.51；24月龄 = 6.01±0.67克/平方毫米）。3月龄动物中APD75与DT的相关系数（r值）很强（r = 0.99），但随年龄增加而减弱（6月龄 = 0.93；12月龄 = 0.81；24月龄 = 0.57）。当APD75与张力峰值时间（TPT）相关时观察到类似结果（3月龄 = 0.95；6月龄 = 0.98；12月龄 = 0.85；24月龄 = 0.68），与半松弛时间（T1/2R）相关时（3月龄 = 0.91；6月龄 = 0.97；12月龄 = 0.85；24月龄 = 0.81）以及与缩短峰值时间（TPS）相关时（3月龄 = 0.89；6月龄 = 0.81；12月龄 = 0.82；24月龄 = 0.51）。加入维拉帕米（V）后，所有年龄组动作电位时程与收缩参数之间的相关性均变弱。3月龄动物中加入V后APD75与DT的相关性降低了34%，而24月龄动物中降低了70%。当向灌注液中加入V时，APD75与TPT、T1/2R和TPS相关时也观察到类似结果。我们的结果表明，兴奋 - 收缩偶联不仅在收缩装置而且在表面膜中发生改变，这可能随年龄而在心室肌中发生改变。
