Correlation of the Glycoside Response− the Force Staircase− and the Action Potential Configuration in the Neonatal Rat Heart
Correlation of the Glycoside Response− the Force Staircase− and the Action Potential Configuration in the Neonatal Rat Heart
复制标题
新生大鼠心脏中糖苷反应-力阶梯-与动作电位配置的相关性
作者：
G. Langer;A. J. Brady;S. T. Tan;S. Serena
大鼠心脏表现出显着的变化，其响应哇巴因和刺激频率增加，并在其动作电位的持续时间在最初的21天的生活。在6.2日龄时，5 × 10− 5 m哇巴因使dP/dt增加158.2%，而在21.1日龄时增加17.2%（P < 0.001）。在6.2天时，当心率从30次/min加速到90次/min时，dP/dt增加了53.4%，而在21.1天时增加了12.2%（P <0.005）。当用含有50% [Na+] 0和25% [Ca 2 +] 0（[Ca 2 +] 0/[Na+] 0 2保持恒定）的溶液灌注心脏时，年轻时的阳性糖苷和阶梯反应几乎被消除。心室动作电位的持续时间从出生时的350-400毫秒逐渐下降到出生后21天的100-150毫秒。这种降低是由于平台期的电位水平缩短和降低所致。用50% [Na+]o灌注显著减少了新生儿早期典型的显著平台期。结果表明，Na+通量通过一个缓慢的膜通道起着重要的作用，在积极的楼梯和糖苷反应的早期新生大鼠心脏。随着心脏发育成熟，与其他哺乳动物相比，心脏功能变得异常，慢通道逐渐关闭。
The rat heart demonstrates marked alterations in its responses to ouabain and increased frequencies of stimulation and in the duration of its action potential during the initial 21 days of life. At an age of 6.2 days 5 × 10−5m ouabain produced a 158.2% increase in dP/dt compared with a 17.2% increase at 21.1 days (P < 0.001). At 6.2 days dP/dt increased by 53.4% when the heart rate was accelerated from 30 to 90 beats/min compared with an increase of 12.2% at 21.1 days (P ≪ 0.005). The positive glycoside and staircase responses at the younger age were virtually eliminated when the hearts were perfused with a solution containing 50% [Na+]o and 25% [Ca2+]o ([Ca2+]o/[Na+]02 maintained constant). The duration of the ventricular action potential progressively decreased from 350–400 msec at birth to 100–150 msec at 21 days of life. This decrease was due to a shortening and a decrease in the potential level of the plateau phase. The prominent plateau typical of the early neonatal period was significantly diminished by perfusion with 50% [Na+]o. The results suggest that Na+ flux through a slow membrane channel plays a significant role in the positive staircase and glycoside responses of the early neonatal rat heart. As the heart matures and becomes functionally anomalous relative to other mammalian species, the slow channel progressively closes.