Na:K pump abundance and function in MDCK cells: effect of low ambient potassium.
Side-specific expression and activity of Na:K pump was studied in Madin-Darby canine kidney (MDCK) cells, a tissue culture model of distal renal tubular epithelium, exposed to low ambient potassium. Confluent monolayers grown on teflon filters in dual chambers were treated with a low K+ medium from 45 min to 72 h. After both acute (45 min) and longer-term (24-72 h) exposure to low K+ (0.7 mM), cation cycling rate of existing pump units increased substantially, while there was no significant change in total cell Na-K-ATPase activity or in basolateral surface pump density. Although a small quantity of Na:K pumps (less than 10%) was consistently present apically, it also did not increase after exposure to low K+, or when the monolayers were provided K+ only from the apical side. In MDCK monolayers low K+ enhances the rate of K+ uptake by the existing pump units but does not increase the total number of pumps or their deployment on either cell surface.
Kumar
S
S
Department of Medicine, University of Chicago, Pritzker School of Medicine, Ill.
Berg
J A
JA
Katz
A I
AI
D000818:Animals; D001693:Biological Transport, Active; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D004285:Dogs; D004848:Epithelium / Q000502:physiology; D007668:Kidney; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium