Separate regulatory control of apical and basolateral Na+/H+ exchange in renal epithelial cells.
Epithelial layers of LLC-PK1/PKE20 cells, a renal epithelial cell line which expresses Na+/H+ exchange activities in the apical as well as basolateral membrane domains, are examined in the single cell mode by microspectrofluorometry. We provide evidence that basolateral Na+/H+ exchange is more sensitive to amiloride inhibition than is apical Na+/H+ exchange. Furthermore, we demonstrate that the two exchange activities differ in their regulatory control: kinase A activation (forskolin, 8-Br-cAMP) leads to inhibition of both exchange activities, whereas kinase C activation (phorbol ester) stimulates basolateral and inhibits apical Na+/H+ exchange. Thus, renal epithelial cells may contain two Na+/H+ exchange activities: an apical ("epithelial") and basolateral ("housekeeping") which may serve different cellular functions and are under separate regulatory controls.
Casavola
V
V
Department of Physiology, University of Zurich, Switzerland.
Helmle-Kolb
C
C
Murer
H
H
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation; D004848:Epithelium / Q000378:metabolism; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007668:Kidney; D007700:Kinetics; D011494:Protein Kinases / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000584:Amiloride; D012964:Sodium; D011494:Protein Kinases; D013755:Tetradecanoylphorbol Acetate