Mansourati J, Le Grand B
Laboratoire de Physiologie Cellulaire, Centre National de Recherche Scientifique, Orsay, France.
Am J Physiol. 1993 Oct;265(4 Pt 2):H1466-70. doi: 10.1152/ajpheart.1993.265.4.H1466.
In human atrial fibers, the action potential undergoes a major developmental change in shape in the months immediately after birth. Transient potassium outward currents, which may affect the shape of the action potential, have been studied using a whole cell voltage-clamp technique with single cells from the atria of young patients aged 3-60 mo. Transient outward current (I(to)) amplitude was measured as the difference between the peak current and the steady-state outward current (I(late)) at the end of the voltage step. The density of I(to) was significantly reduced in adult diseased cells (n = 18) compared with normal cells (n = 21) in a large range of potential and absent in young diseased cells (n = 13). Furthermore, the I(late) recorded in young cells was significantly greater (23.7 +/- 5.74 pA/pF at 60 mV) than in adult normal cells (12.71 +/- 2.25 pA/pF at 60 mV), whereas I(late) was not significantly different between both groups of adult cells. Nevertheless, a 4-aminopyridine-sensitive I(to) has been recorded in young cells. A decrease in the frequency of clamp steps (from 0.1 to 0.01 Hz) did not reactivate a I(to) in young cells. This absence of 4-aminopyridine-sensitive Ito in young cells probably results from either a normal developmental change of this current or from pathological alterations like those described in adult diseased atria.
在人类心房纤维中，动作电位在出生后的数月内形状会发生重大的发育变化。利用全细胞膜片钳技术，对3至60个月大的年轻患者心房的单个细胞进行研究，探讨了可能影响动作电位形状的瞬时外向钾电流。瞬时外向电流（I(to)）幅度通过电压阶跃结束时的峰值电流与稳态外向电流（I(late)）之间的差值来测量。在较大电位范围内，成年患病细胞（n = 18）的I(to)密度相较于正常细胞（n = 21）显著降低，而年轻患病细胞（n = 13）中则不存在I(to)。此外，年轻细胞中记录到的I(late)显著大于成年正常细胞（60 mV时为23.7 +/- 5.74 pA/pF）（60 mV时为12.71 +/- 2.25 pA/pF），而两组成年细胞之间的I(late)并无显著差异。然而，在年轻细胞中记录到了对4 - 氨基吡啶敏感的I(to)。钳制步长频率降低（从0.1 Hz降至0.01 Hz）并未使年轻细胞中的I(to)重新激活。年轻细胞中缺乏对4 - 氨基吡啶敏感的Ito可能是由于该电流的正常发育变化，或者是由于类似成年患病心房中所描述的病理改变。
