Masuda H, Sperelakis N
Department of Physiology and Biophysics, College of Medicine, University of Cincinnati, Ohio 45267-0576.
Am J Physiol. 1993 Oct;265(4 Pt 2):H1107-11. doi: 10.1152/ajpheart.1993.265.4.H1107.
Whole cell and single-channel inwardly rectifying potassium currents (IK1) of freshly isolated single fetal (12 and 18 days) and neonatal (1, 5, and 10 days) rat ventricular myocytes were recorded using patch-clamp techniques. Whole cell IK1 was elicited by hyperpolarizing test pulses from a holding potential of -40 mV. IK1 densities increased markedly during heart development between fetal day 12 and until neonatal day 5; there was no further increase on neonatal day 10. Cell-attached patch recordings of single IK1 channels were employed with 150 mM K+ both in the pipette and bath solutions. Large-conductance (31 pS) K+ channels with short openings were observed both in fetal day 18 and neonatal day 5 but not in fetal day 12 cells. Only small-conductance (11 pS) channels with long openings were observed in approximately 10% of the cells on fetal day 12. The open probability of the large-conductance channels was 2.6-fold greater on neonatal day 5 than on fetal day 18. In conclusion, the increase in the IK1 density during observed heart development may be primarily due to an increase in the open probability of the IK1 channels, rather than to an increase in their number. We suggest that the small-conductance channel infrequently observed on fetal day 12 could be an immature type of IK1 channel, which disappears during development.
采用膜片钳技术记录了新鲜分离的单个胎儿（12天和18天）及新生大鼠（1天、5天和10天）心室肌细胞的全细胞和单通道内向整流钾电流（IK1）。全细胞IK1由从-40 mV的钳制电位进行超极化测试脉冲诱发。在心脏发育过程中，从胎儿12天到新生5天期间，IK1密度显著增加；新生10天时没有进一步增加。在移液管和浴液中均含有150 mM K+的情况下，采用单IK1通道的细胞贴附式膜片钳记录。在胎儿18天和新生5天的细胞中均观察到具有短开放时间的大电导（31 pS）K+通道，但在胎儿12天的细胞中未观察到。在胎儿12天的约10%的细胞中仅观察到具有长开放时间的小电导（11 pS）通道。大电导通道的开放概率在新生5天比在胎儿18天高2.6倍。总之，在观察到的心脏发育过程中IK1密度的增加可能主要是由于IK1通道开放概率的增加，而不是其数量的增加。我们认为在胎儿12天很少观察到的小电导通道可能是一种不成熟的IK1通道类型，其在发育过程中消失。
