Wu M H, Su M J, Lue H C
Department of Pediatrics, College of Medicine, National Taiwan University, Taipei, R.O.C.
Zhonghua Min Guo Xiao Er Ke Yi Xue Hui Za Zhi. 1992 Sep-Oct;33(5):363-71.
In accord with previous reports, we have found that action potentials triggered from isolated mature (> 1 month) guinea-pig ventricular myocytes showed a longer duration than those from the neonate (< 1 day). A whole-cell voltage-clamp technique has been used to identify the postnatal changes of inward rectifier (Ikl) and delayed outward potassium currents (Ik), which may be related to the action potential transition. Our results have shown that the degree of maturation of the neonatal guinea-pig is much advanced, as compared to neonatal rabbits and rats. Slope conductance (1230 +/- 110 pS/pF, n = 10, for neonatal, and 1450 +/- 450 pS/pF, n = 10, for mature guinea-pig, p > 0.05) and the inward rectification occurring over a potential range from -50 to -10 mV were relatively similar between the neonatal and mature guinea-pig myocytes. But, the slope conductance of Ik was significantly greater in neonatal (702 +/- 80 pS/pF, n = 10) guinea-pig myocytes than in the mature (194 +/- 23 pS/pF, n = 10, p < 0.01). Therefore, we suggest that (1) the maturation of Ik appears later than that of Ikl, (2) age-related decrease of the slope conductance of Ik could contribute to an age-related lengthening of the action potential duration.
与先前的报道一致，我们发现，从分离的成熟（>1个月）豚鼠心室肌细胞触发的动作电位持续时间比新生（<1天）的细胞更长。采用全细胞膜片钳技术来确定内向整流钾电流（Ikl）和延迟外向钾电流（Ik）的出生后变化，这些变化可能与动作电位的转变有关。我们的结果表明，与新生兔和大鼠相比，新生豚鼠的成熟程度要高得多。新生豚鼠和成熟豚鼠心肌细胞的斜率电导（新生豚鼠为1230±110 pS/pF，n = 10；成熟豚鼠为1450±450 pS/pF，n = 10，p>0.05）以及在-50至-10 mV电位范围内发生的内向整流相对相似。但是，新生豚鼠心肌细胞的Ik斜率电导（702±80 pS/pF，n = 10）显著大于成熟豚鼠（194±23 pS/pF，n = 10，p<0.01）。因此，我们认为：（1）Ik的成熟比Ikl出现得晚；（2）与年龄相关的Ik斜率电导降低可能导致动作电位持续时间随年龄增长而延长。
