AJP - Renal Physiology, Vol 270, Issue 1 116-F122, Copyright © 1996 by American Physiological Society

ARTICLES

Functional activity of H-K-ATPase in individual cells of OMCD: localization and effect of K+ depletion

M. Kuwahara, W. J. Fu and F. Marumo
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.

Recent studies have indicated the presence of hydrogen-potassium-adenosinetriphosphatase (H-K-ATPase) in the collecting duct. We examined the localization of functional H-K-ATPase activity in individual cells of the outer and inner stripes of outer medullary collecting ducts (OMCDo and OMCDi). Tubules were isolated from control and K(+)-depleted rabbits and perfused in vitro. Intracellular pH (pHi) of principal cells, intercalated cells, and OMCDi cells was monitored by fluorescence ratio imaging using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). An intracellular acid load was induced by NH3/NH4 prepulse in extracellular Na(+)-, K(+)-, and HCO3(-)-free condition, and then 5 mM K+ was added to the lumen or the bath in the presence of Ba2+. Functional activity of H-K-ATPase was estimated by the difference in the rates of pHi recovery before and after K+ addition. In the control condition, luminal addition of K+ significantly increased the pHi recovery rate by 1.6 +/- 0.4 and 1.9 +/- 0.4 x 10(-3) pH units/s in intercalated calls and OMCDi cells, respectively, but not in principal cells. This K(+)-dependent pHi recovery was inhibited by 63% in intercalated cells and 74% in OMCDi cells in the presence of luminal Sch-28080 (10 microM) but was not affected in the presence of luminal bafilomycin-A1 (10 nM). K+ depletion increased the K(+)-dependent pHi recovery to 2.3-fold in intercalated cells and 2.6-fold in OMCDi cells. By contrast, K(+)-dependent pHi recovery was not detected in the basolateral membrane of any cell types in either the control or the K(+)-depleted condition. These results provide functional evidence that H-K-ATPase is distributed in the luminal membrane of intercalated cells and OMCDi cells and that this ATPase is activated by K+ depletion, suggesting the contribution of intercalated cells and OMCDi cells to K+ conservation in rabbit OMCD.

This article has been cited by other articles:

				C. A. Wagner, K. E. Finberg, S. Breton, V. Marshansky, D. Brown, and J. P. Geibel Renal Vacuolar H+-ATPase Physiol Rev, October 1, 2004; 84(4): 1263 - 1314. [Abstract] [Full Text] [PDF]

				S. Nakamura Glucose activates H+-ATPase in kidney epithelial cells Am J Physiol Cell Physiol, July 1, 2004; 287(1): C97 - C105. [Abstract] [Full Text] [PDF]

				X. Zhou, S. Nakamura, S.-L. Xia, and C. S. Wingo Increased CO2 stimulates K/Rb reabsorption mediated by H-K-ATPase in CCD of potassium-restricted rabbit Am J Physiol Renal Physiol, August 1, 2001; 281(2): F366 - F373. [Abstract] [Full Text] [PDF]

				S. Muto Potassium Transport in the Mammalian Collecting Duct Physiol Rev, January 1, 2001; 81(1): 85 - 116. [Abstract] [Full Text] [PDF]

				A. M. Weinstein A mathematical model of the outer medullary collecting duct of the rat Am J Physiol Renal Physiol, July 1, 2000; 279(1): F24 - F45. [Abstract] [Full Text] [PDF]

				R. B. Silver and M. Soleimani H+-K+-ATPases: regulation and role in pathophysiological states Am J Physiol Renal Physiol, June 1, 1999; 276(6): F799 - F811. [Abstract] [Full Text] [PDF]

				I. D. Weiner, A. E. Frank, and C. S. Wingo Apical proton secretion by the inner stripe of the outer medullary collecting duct Am J Physiol Renal Physiol, April 1, 1999; 276(4): F606 - F613. [Abstract] [Full Text] [PDF]

				S. Nakamura, Z. Wang, J. H. Galla, and M. Soleimani K+ depletion increases HCO−3 reabsorption in OMCD by activation of colonic H+-K+-ATPase Am J Physiol Renal Physiol, April 1, 1998; 274(4): F687 - F692. [Abstract] [Full Text] [PDF]

				B. C. Kone and S. C. Higham A Novel N-terminal Splice Variant of the Rat H+-K+-ATPase alpha 2 Subunit. CLONING, FUNCTIONAL EXPRESSION, AND RENAL ADAPTIVE RESPONSE TO CHRONIC HYPOKALEMIA J. Biol. Chem., January 30, 1998; 273(5): 2543 - 2552. [Abstract] [Full Text] [PDF]