Potassium secretion by the cortical collecting tubule: effect of C1 gradients and ouabain.
In various epithelia K and Cl transport are molecularly coupled and KCl cotransport is dependent on the Na-K pump. The present study examines 1) the effect of a bath-to-lumen Cl gradient on K secretion during active Na transport and 2) the effect of basolateral ouabain on K secretion and Na absorption in the presence and the absence of a bath-to-lumen Cl gradient. Under symmetrical conditions there was significant K secretion (JK = -24.0 +/- 3.9 pmol.mm-1.min-1) and Cl secretion (JCl = -15.7 +/- 3.7 pmol.mm-1.min-1). Transepithelial voltage (VT) was significantly lumen negative (-25.3 +/- 5.9 mV), and Cl secretion occurred against its electrochemical gradient by a transcellular mechanism. Increasing bath [Cl] did not hyperpolarize VT; in fact there was a tendency for VT to depolarize and K secretion was not stimulated. However, ouabain significantly inhibited active Cl secretion and net Na absorption both in the presence and absence of a bath-to-lumen Cl gradient. Furthermore, ouabain totally inhibited K secretion in the absence of external ion gradients but inhibited K secretion by only 50% in the presence of a bath-to-lumen Cl gradient. This ouabain-insensitive K secretion exhibited a codependence on Cl secretion. Thus K secretion may occur passively, utilizing Cl movement down its electrochemical gradient when active Na transport is inhibited by ouabain. The results are compatible with the presence of a Cl-linked K-secretory process in the rabbit CCT.(ABSTRACT TRUNCATED AT 250 WORDS)
Wingo
C S
CS
Department of Medicine, College of Medicine, University of Florida, Gainesville.
D000818:Animals; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology*; D004848:Epithelium / Q000502:physiology; D005260:Female; D007672:Kidney Cortex / Q000187:drug effects / Q000502:physiology*; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012016:Reference Values; D012964:Sodium / Q000378:metabolism
D002712:Chlorides; D010042:Ouabain; D012964:Sodium; D011188:Potassium