K+ depletion increases HCO3- reabsorption in OMCD by activation of colonic H(+)-K(+)-ATPase

Am J Physiol. 1998 Apr;274(4):F687-92. doi: 10.1152/ajprenal.1998.274.4.F687.

Abstract

To probe the role of the isoforms of H(+)-K(+)-ATPase (HKA) in potassium depletion (KD), rats were placed on a KD diet for 2 wk. Colonic HKA (cHKA) mRNA levels increased approximately 30-fold in outer medulla, and net HCO3-flux (JtCO2) in outer medullary collecting duct (OMCD) increased (13.1 pmol.min-1.mm tubule length-1 in control to 17.7 pmol.min-1.mm tubule length-1 in KD; P < 0.01). In normal rats, 1 mM ouabain in perfusate had no effect on JtCO2, whereas 10 microM Sch-28080 decreased JtCO2 to 5.1 pmol.min-1.mm tubule length-1 (P < 0.001). In KD rats, ouabain 1 mM decreased JtCO2 to 6.3 pmol.min-1.mm tubule length-1 (P < 0.001). Although 10 microM Sch-28080 also decreased JtCO2 to 4.6 pmol.min-1.mm tubule length-1 (P < 0.001), the inhibitory effects of Sch-28080 and ouabain were not additive. Removal of K+ from perfusate blocked Sch-28080-sensitive JtCO2 in both normal and KD tubules. The data suggest that, in KD, cHKA is induced and mediates increased HCO3-reabsorption in OMCD, cHKA in vivo is sensitive to both Sch-28080 and ouabain, and cHKA activity is dominant.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Absorption / physiology
  • Animals
  • Bicarbonates / metabolism*
  • Colon / enzymology*
  • Enzyme Activation / physiology
  • Enzyme Inhibitors / pharmacology
  • H(+)-K(+)-Exchanging ATPase / genetics
  • H(+)-K(+)-Exchanging ATPase / metabolism*
  • Imidazoles / pharmacology
  • Isoenzymes / metabolism
  • Kidney Medulla
  • Kidney Tubules, Collecting / metabolism*
  • Male
  • Ouabain / pharmacology
  • Potassium Deficiency / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Reference Values

Substances

  • Bicarbonates
  • Enzyme Inhibitors
  • Imidazoles
  • Isoenzymes
  • RNA, Messenger
  • Sch 28080
  • Ouabain
  • H(+)-K(+)-Exchanging ATPase