Potassium channels along the nephron.
The K+ channels that are present in three different nephron segments, the Necturus proximal, Amphiuma early distal (diluting segment), and rabbit collecting tubule have been examined. Ca2+-sensitive K+ channels were present in the apical membranes of the cells lining all these segments. The channels were all voltage-sensitive and their open probability increased with membrane depolarization. Because of the ubiquitous distribution, it is suggested that this channel is responsible for K+ secretion by the nephron and that the same intracellular regulators act throughout the various segments. Basolateral K+ channels have been examined only in Necturus proximal tubules. This channel is apparently insensitive to Ca2+; the voltage dependence is exactly opposite to that of the apical K+ channels; that is, hyperpolarizing potentials caused an increase in open probability. These differences in regulatory factors permit the independent regulation of apical and basolateral membrane K+ permeabilities that must occur in renal cells.
D000818:Animals; D002118:Calcium / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000502:physiology; D009337:Necturus; D009399:Nephrons / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D014562:Caudata
D007473:Ion Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium