Basolateral membrane potassium channels in rabbit cortical thick ascending limb.
The nature of K exit across the basolateral membrane of rabbit cortical thick ascending limb (CTAL) was investigated using the patch clamp technique. The basolateral membrane was exposed by mild collagenase treatment (0.1 U/ml), and a K-selective inwardly rectifying channel was identified. In cell-attached patches (140 mM K pipette) the inward conductance was 35.0 +/- 1.3 pS (n = 9) compared with an outward conductance of 7.0 +/- 0.9 pS (n = 5), and the current reversed at a pipette potential of -63.5 +/- 3.1 mV (n = 9). The channel is strongly voltage dependent, showing an e-fold increase in open probability per 18-mV depolarization. Barium blocked the channel, reducing both mean open probability and single-channel current amplitude; however, the channel was not Ca sensitive. On excision the channel exhibited rundown, which could not be prevented by 0.1 mM ATP or ATP plus 20 U/ml catalytic subunit of protein kinase A. A few excised patch recordings were possible, which confirmed the presence of a highly K-selective channel with a K-to-Na permeability ratio of 100. In conclusion, 1) it is possible to obtain patch clamp recordings from the rabbit CTAL basolateral membrane using a very mild collagenase treatment, and 2) the exit of K across the basolateral membrane is mediated at least in part by the presence of voltage-sensitive K channels.
Hurst
A M
AM
Membrane Transport Research Group, Université de Montréal, Quebec, Canada.
Duplain
M
M
Lapointe
J Y
JY
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004594:Electrophysiology; D007425:Intracellular Membranes / Q000378:metabolism; D007672:Kidney Cortex; D008138:Loop of Henle / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011817:Rabbits
D015221:Potassium Channels; D001464:Barium; D002118:Calcium