AJP - Renal Physiology, Vol 266, Issue 6 868-F877, Copyright © 1994 by American Physiological Society

ARTICLES

H(+)-ATPases of renal cortical and medullary endosomes are differentially sensitive to Sch-28080 and omeprazole

I. Sabolic, D. Brown, J. M. Verbavatz and J. Kleinman
Renal Unit, Massachusetts General Hospital, Boston.

Adenosinetriphosphatase (ATPase) activity stimulated by K+ and inhibited by Sch-28080 (SCH), omeprazole (OME), and vanadate has been measured in microsomes from mammalian renal medulla and attributed to a kidney isoform of the H(+)-K(+)-ATPase. To determine whether the H(+)-K(+)-ATPase inhibitors could also inhibit the vacuolar (V)-type H(+)-adenosinetriphosphatase (H(+)-ATPase, i.e., H+ pump) in mammalian intracellular vesicles, we examined their effects on bafilomycin-sensitive acidification in renal cortical vesicles (CEV) and medullary endocytic vesicles (MEV). Rats were injected with fluorescein isothiocyanate-labeled dextran, and labeled endosomes were enriched from kidney tissue homogenates by differential and Percoll density gradient centrifugation. In the CEV, the V-type H+ pump was inhibited 25% by SCH and 30% by OME (100 microM each). Whereas the inhibition by OME was concentration and time dependent, the inhibition by SCH was only concentration dependent. Inhibition by these compounds was similar in the presence of 50 mM K+ (in = out) and in the complete absence of K+, thus ruling out a significant involvement of H(+)-K(+)-ATPase-mediated acidification. Inhibition, however, was not observed with 10 microM SCH and OME. The sensitivity of the V-type H+ pump to 100 microM SCH and OME in CEV was confirmed by the comparable inhibitions of intravesicular acidification observed in acridine orange fluorescence quench studies and by inhibition of Pi liberation in an ATPase assay. We also found that the V-type H+ pump in isolated rat liver endosomes is sensitive to 100 microM SCH and OME to a similar degree. In the MEV, acidification was only weakly affected by 100 microM SCH and OME, thus suggesting that H(+)-ATPases in endosomes from cortical and medullary tubules are different, possibly due to a previously described selective expression of subunit isoforms. Our finding indicates the importance of using low concentrations (< 10 microM) of OME and SCH in studies of H(+)-K(+)-ATPase in nongastric tissues to avoid misinterpretation of the data due to nonspecific inhibition of V-type H(+)-ATPases.

This article has been cited by other articles:

				N. W. G. Lambrecht, I. Yakubov, C. Zer, and G. Sachs Transcriptomes of purified gastric ECL and parietal cells: identification of a novel pathway regulating acid secretion Physiol Genomics, March 13, 2006; 25(1): 153 - 165. [Abstract] [Full Text] [PDF]

				S. J. YOUMANS and C. R. BARRY BAFILOMYCIN A1 AT NANOMOLAR CONCENTRATIONS SATURABLY INHIBITS A PORTION OF TURTLE BLADDER ACIDIFICATION CURRENT J. Exp. Biol., March 10, 2002; 204(16): 2911 - 2919. [Abstract] [Full Text] [PDF]

				J. Codina, J. Cardwell, J. J. Gitomer, Y. Cui, B. C. Kone, and T. D. Dubose Jr. Sch-28080 depletes intracellular ATP selectively in mIMCD-3 cells Am J Physiol Cell Physiol, November 1, 2000; 279(5): C1319 - C1326. [Abstract] [Full Text] [PDF]

				C. E. Gustafson, T. Katsura, M. McKee, R. Bouley, J. E. Casanova, and D. Brown Recycling of AQP2 occurs through a temperature- and bafilomycin-sensitive trans-Golgi-associated compartment Am J Physiol Renal Physiol, February 1, 2000; 278(2): F317 - F326. [Abstract] [Full Text] [PDF]

				H. Amlal, Z. Wang, and M. Soleimani Functional upregulation of H+-ATPase by lethal acid stress in cultured inner medullary collecting duct cells Am J Physiol Cell Physiol, October 1, 1997; 273(4): C1194 - C1205. [Abstract] [Full Text] [PDF]

				S. Petrovic, Z. Spicer, T. Greeley, G. E Shull, and M. Soleimani Novel Schering and ouabain-insensitive potassium-dependent proton secretion in the mouse cortical collecting duct Am J Physiol Renal Physiol, January 1, 2002; 282(1): F133 - F143. [Abstract] [Full Text] [PDF]