PDF(Pubmed)
Abstract：
Basolateral potassium channels in the distal convoluted tubule (DCT) are composed of inwardly-rectifying potassium channel 4.1 (Kir4.1) and Kir5.1. Kir4.1 interacts with Kir5.1 to form a 40 pS K+ channel which is the only type K+ channel expressed in the basolateral membrane of the DCT. Moreover, Kir4.1/Kir5.1 heterotetramer plays a key role in determining the expression and activity of thiazide-sensitive Na-Cl cotransport (NCC). In addition to Kir4.1/Kir5.1, Kir1.1 (ROMK) is expressed in the apical membrane of the late DCT (DCT2) and plays a key role in mediating epithelial Na+ channel (ENaC)-dependent K+ excretion. High dietary-K+-intake (HK) stimulates ROMK and inhibits Kir4.1/Kir5.1 in the DCT. Inhibition of Kir4.1/Kir5.1 is essential for HK-induced suppression of NCC whereas the stimulation of ROMK is important for increasing ENaC-dependent K+ excretion during HK. We have now used the patch-clamp-technique to examine whether gender and Cl- content of K+-diet affect HK-induced inhibition of basolateral Kir4.1/Kir5.1 and HK-induced stimulation of ROMK. Single-channel-recording shows that basolateral 40 pS K+ channel (Kir4.1/Kir5.1) activity of the DCT defined by NPo was 1.34 (1% KCl, normal K, NK), 0.95 (5% KCl) and 1.03 (5% K+-citrate) in male mice while it was 1.47, 1.02 and 1.05 in female mice. The whole-cell recording shows that Kir4.1/Kir5.1-mediated-K+ current of the early-DCT (DCT1) was 1,170 pA (NK), 725 pA (5% KCl) and 700 pA (5% K+-citrate) in male mice whereas it was 1,125 pA, 674 pA and 700 pA in female mice. Moreover, K+-currents (IK) reversal potential of DCT (an index of membrane potential) was -63 mV (NK), -49 mV (5% KCl) and -49 mV (5% K-citrate) in the male mice whereas it was -63 mV, -50 mV and -50 mV in female mice. Finally, TPNQ-sensitive whole-cell ROMK-currents in the DCT2 /initial-connecting tubule (CNT) were 910 pA (NK), 1,520 pA (5% KCl) and 1,540 pA (5% K+-citrate) in male mice whereas the ROMK-mediated K+ currents were 1,005 pA, 1,590 pA and 1,570 pA in female mice. We conclude that the effect of HK intake on Kir4.1/Kir5.1 of the DCT and ROMK of DCT2/CNT is similar between male and female mice. Also, Cl- content in HK diets has no effect on HK-induced inhibition of Kir4.1/Kir5.1 of the DCT and HK-induced stimulation of ROMK in DCT2/CNT.
摘要：
远曲小管（DCT）的基底外侧钾通道由向内整流钾通道4.1（Kir4.1）和Kir5.1组成。Kir4.1与Kir5.1相互作用形成40pSK通道，这是DCT基底外侧膜中表达的唯一K型通道。此外，Kir4.1/Kir5.1异四聚体在决定噻嗪敏感的Na-Cl共转运（NCC）的表达和活性中起关键作用。除Kir4.1/Kir5.1外，Kir1.1（ROMK）在晚期DCT（DCT2）的顶膜中表达，并在介导上皮Na通道（ENaC）依赖性K排泄中起关键作用。高膳食K+摄入量(HK)刺激ROMK并抑制DCT中的Kir4.1/Kir5.1。Kir4.1/Kir5.1的抑制对于HK诱导的NCC抑制是必需的,而ROMK的刺激对于在HK期间增加ENaC依赖性的K+排泄是重要的。我们现在已经使用膜片钳技术来检查K饮食的性别和Cl-含量是否影响HK诱导的基底外侧Kir4.1/Kir5.1的抑制和HK诱导的ROMK刺激。单通道记录显示，NPo定义的DCT的基底外侧40pSK通道（Kir4.1/Kir5.1）活性为1.34（1％KCl，正常K,NK),在雄性小鼠中为0.95(5%KCl)和1.03(5%K+-柠檬酸盐),而在雌性小鼠中为1.47、1.02和1.05。全细胞记录显示，早期DCT（DCT1）的Kir4.1/Kir5.1介导的K电流为1,170pA（NK），雄性小鼠的725pA（5％KCl）和700pA（5％K柠檬酸盐），而为1,125pA，雌性小鼠中的674pA和700pA。此外，DCT的K+电流(IK)反转电位(膜电位指数)为-63mV(NK),在雄性小鼠中-49mV（5％KCl）和-49mV（5％柠檬酸钾），而它是-63mV，雌性小鼠中的-50mV和-50mV。最后,DCT2/初始连接小管（CNT）中的TPNQ敏感的全细胞ROMK电流为910pA（NK），雄性小鼠的1,520pA（5％KCl）和1,540pA（5％柠檬酸钾），而ROMK介导的K电流为1,005pA，雌性小鼠中的1,590pA和1,570pA。我们得出的结论是，在雄性和雌性小鼠之间，HK摄入对DCT的Kir4.1/Kir5.1和DCT2/CNT的ROMK的影响相似。此外，HK饮食中的Cl-含量对HK诱导的DCT的Kir4.1/Kir5.1抑制和HK诱导的DCT2/CNT中的ROMK刺激没有影响。
