Hurst A M, Beck J S, Laprade R, Lapointe J Y
Groupe de Recherche en Transport Membranaire, Université de Montréal, Quebec, Canada.
Am J Physiol. 1993 Apr;264(4 Pt 2):F760-4. doi: 10.1152/ajprenal.1993.264.4.F760.
In several epithelial and nonepithelial tissues a functional link between the basolateral Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) and a basolateral K+ conductance has been established. However, the nature of this link is unclear. We have previously identified a K+ channel on the basolateral membrane of the proximal convoluted tubule perfused in vitro, the activity of which is increased by stimulation of Na+ transport [J. S. Beck, A. M. Hurst, J.-Y. Lapointe, and R. Laprade. Am. J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F496-F501, 1993]. In the present study we investigate whether basolateral membrane K+ channel activity is tightly coupled to Na(+)-K(+)-ATPase activity. In cell-attached patches (150 mM K+ pipette), following stimulation of channel activity by addition of Na(+)-cotransported solutes to the tubule lumen, mean channel open probability (NPo) was reduced from 0.35 +/- 0.09 to 0.14 +/- 0.06 (n = 7, P < 0.05) by blocking the Na(+)-K(+)-ATPase with 100 microM strophanthidin. In excised patches the channel was reversibly blocked by 2 mM ATP from the cytosolic face of the patch, such that NPo fell to 20.1 +/- 7.0% (n = 5, P < 0.001) of control and recovered to 52.2 +/- 11.2% (n = 5, P < 0.05) after washout of ATP. Diazoxide, a putative opener of ATP-sensitive K+ channels, when added to the bathing solution of an unstimulated tubule (microperfused in the absence of Na(+)-cotransported solutes), increased NPo from 0.046 +/- 0.035 to 0.44 +/- 0.2 (n = 6, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
在几种上皮组织和非上皮组织中，已证实基底外侧钠钾三磷酸腺苷酶（Na(+)-K(+)-ATP酶）与基底外侧钾离子电导之间存在功能联系。然而，这种联系的本质尚不清楚。我们之前在体外灌注的近端曲管基底外侧膜上鉴定出一种钾离子通道，通过刺激钠离子转运可增强其活性[J. S. 贝克、A. M. 赫斯特、J.-Y. 拉波因特和R. 拉普拉德。《美国生理学杂志》264卷（肾流体电解质生理学33）：F496 - F501，1993年]。在本研究中，我们探究基底外侧膜钾离子通道活性是否与Na(+)-K(+)-ATP酶活性紧密耦合。在细胞贴附片（移液管内钾离子浓度为150 mM）中，向肾小管管腔添加与钠共转运的溶质刺激通道活性后，用100 μM毒毛花苷阻断Na(+)-K(+)-ATP酶，平均通道开放概率（NPo）从0.35 ± 0.09降至0.14 ± 0.06（n = 7，P < 0.05）。在切除的膜片中，该通道可被来自膜片胞质面的2 mM ATP可逆性阻断，使得NPo降至对照值的20.1 ± 7.0%（n = 5，P < 0.001），洗脱ATP后恢复至52.2 ± 11.2%（n = 5，P < 0.05）。二氮嗪，一种推测的ATP敏感性钾离子通道开放剂，添加到未受刺激的肾小管（在无与钠共转运溶质的情况下进行微量灌注）的浴液中时，可使NPo从0.046 ± 0.035增加至0.44 ± 0.2（n = 6，P < 0.05）。（摘要截短于250字）
