A Ca2-activated cation-selective channel in the basolateral membrane of the cortical thick ascending limb of Henle's loop of the mouse.
The patch-clamp technique was used to investigate the properties of a cation-selective channel in the basolateral membrane of microdissected collagenase-treated fragments of cortical thick ascending limbs of Henle's loop from mouse kidney. The channel activity was seldom observed in cell-attached patches (2 out 15 studied cases). In inside-out excised patches immersed in symmetrical NaCl Ringer's solutions, the unit channel conductance was ohmic and ranged from 22 to 33 pS (mean, 26.8 +/- 0.6 pS, n = 24). When NaCl was replaced by KCl (n = 8) or sodium gluconate (n = 2) on the cytoplasmic side of the membrane, single-channel currents still reversed at 0 mV and the conductance was unchanged. The reversal potential was +28.8 +/- 0.4 mV (n = 8) when a NaCl concentration (140 vs. 42 mmol/l) gradient was applied, close to the expected value (approx. 30 mV) for a cation selective channel. The channel was found to discriminate poorly between Na+, K+, Cs+, and Li+ ions. The activity of the channel was not clearly voltage-dependent but was dependent upon the free Ca2+ concentration on the cytoplasmic side of the membrane. We conclude that the channel resembles the non-selective cation channel which has been previously described in several tissues.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002412:Cations / Q000378:metabolism*; D002462:Cell Membrane / Q000648:ultrastructure; D002586:Cesium / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D007684:Kidney Tubules / Q000032:analysis*; D008094:Lithium / Q000378:metabolism; D008138:Loop of Henle / Q000032:analysis*; D008297:Male; D051379:Mice; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D002412:Cations; D007473:Ion Channels; D002586:Cesium; D008094:Lithium; D012964:Sodium; D011188:Potassium; D002118:Calcium