PDF(Pubmed)
Abstract：
Background: The basolateral potassium channels play an important role in maintaining the membrane transport in the renal proximal tubules (PT) and adenosine receptors have been shown to regulate the trans-epithelial Na+ absorption in the PT. The aim of the present study is to explore whether adenosine also regulates the basolateral K+ channel of the PT and to determine the adenosine receptor type and the signaling pathway which mediates the effect of adenosine on the K+ channel. Methods: We have used the single channel recording to examine the basolateral K+ channel activity in the proximal tubules of the mouse kidney. All experiments were performed in cell-attached patches. Results: Single channel recording has detected a 50 pS inwardly-rectifying K+ channel with high channel open probability and this 50 pS K+ channel is a predominant type K+ channel in the basolateral membrane of the mouse PT. Adding adenosine increased 50 pS K+ channel activity in cell-attached patches, defined by NPo (a product of channel Numbers and Open Probability). The adenosine-induced stimulation of the 50 pS K+ channel was absent in the PT pretreated with DPCPX, a selective inhibitor of adenosine A1 receptor. In contrast, adenosine was still able to stimulate the 50 pS K+ channel in the PT pretreated with CP-66713, a selective adenosine A2 receptor antagonist. This suggests that the stimulatory effect of adenosine on the 50 pS K+ channel of the PT was mediated by adenosine-A1 receptor. Moreover, the effect of adenosine on the 50 pS K+ channel was blocked in the PT pretreated with U-73122 or Calphostin C, suggesting that adenosine-induced stimulation of the 50 pS K+ channels of the PT was due to the activation of phospholipase C (PLC) and protein kinase C (PKC) pathway. In contrast, the inhibition of phospholipase A2 (PLA2) with AACOCF3 or inhibition of protein kinase A (PKA) with H8 failed to block the adenosine-induced stimulation of the 50 pS K+ channel of the PT. Conclusion: We conclude that adenosine activates the 50 pS K+ channels in the basolateral membrane of PT via adenosine-A1 receptor. Furthermore, the effect of adenosine on the 50 pS K+ channel is mediated by PLC-PKC signaling pathway.
摘要：
背景：基底外侧钾通道在维持肾脏近端小管（PT）的膜运输中起重要作用，腺苷受体已被证明可以调节PT中的跨上皮Na吸收。本研究的目的是探讨腺苷是否也调节PT的基底外侧K通道，并确定腺苷受体类型和介导腺苷对K通道作用的信号通路。方法：我们使用单通道记录来检查小鼠肾脏近端小管的基底外侧K通道活性。所有实验均在细胞附着的贴片中进行。结果：单通道记录已检测到具有高通道开放概率的50pS向内整流K通道，并且该50pSK通道是小鼠PT基底外侧膜中的主要K型通道。在细胞附着的贴片中，添加腺苷增加了50pSK+通道活性，由NPo(通道号和开放概率的乘积)定义。在用DPCPX预处理的PT中不存在腺苷诱导的50pSK通道刺激，腺苷A1受体的选择性抑制剂。相比之下,腺苷仍然能够刺激用选择性腺苷A2受体拮抗剂CP-66713预处理的PT中的50pSK通道。这表明腺苷对PT的50pSK通道的刺激作用是由腺苷A1受体介导的。此外，在用U-73122或CalphostinC预处理的PT中，腺苷对50pSK通道的作用被阻断，表明腺苷诱导的PT的50pSK通道的刺激是由于磷脂酶C（PLC）和蛋白激酶C（PKC）途径的激活。相比之下,AACOCF3抑制磷脂酶A2（PLA2）或H8抑制蛋白激酶A（PKA）未能阻断腺苷诱导的PT50pSK通道的刺激。结论：我们得出结论，腺苷通过腺苷A1受体激活PT基底外侧膜中的50pSK通道。此外，腺苷对50pSK+通道的作用是通过PLC-PKC信号通路介导的。
