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- Title
Colonic H+-K+-ATPase is induced and mediates increased HCO3- reabsorption in inner medullary collecting duct in potassium depletion.
- Authors
Nakamura, Suguru; Amlal, Hassane; Galla, John H; Soleimani, Manoocher; Nakamura, S; Amlal, H; Galla, J H; Soleimani, M
- Abstract
<bold>Background: </bold>Potassium depletion increases HCO3- reabsorption in outer medullary collecting duct (OMCD) by activation of colonic (c) H-K-ATPase (HKA). The purpose of the current experiments was to examine the role of the isoforms of HKA in HCO3- reabsorption by terminal inner medullary collecting duct (IMCD) cells in potassium depletion.<bold>Methods: </bold>Sprague-Dawley rats were fed a potassium-free diet and studied after 8 to 10 days. mRNA expression of HKA isoforms in terminal portion of inner medulla was examined and correlated with HCO3- reabsorption in the terminal IMCD.<bold>Results: </bold>Gastric (g) HKA mRNA decreased whereas colonic (c) HKA mRNA expression was heavily induced in terminal portion of inner medulla in potassium depleted rats. Net HCO3- flux (JtCO2) in terminal IMCD increased in potassium depletion (4.56 to 7.06 pmol/min/mm tubule length, P < 0.001). In normal rats, 1 mM ouabain in perfusate had no effect on JtCO2, whereas 10 microM Schering 28080 (SCH) decreased JtCO2 to 2.4 (P < 0.002). In KD rats, 1 mM ouabain decreased JtCO2 to 4.9 (P < 0.005) and 10 microM SCH decreased JtCO2 to 3.3 (P < 0.001). However, the inhibitory effects of SCH and ouabain on JtCO2 in potassium depleted animals were not additive.<bold>Conclusions: </bold>The data indicate that gHKA is suppressed whereas cHKA is induced in potassium depletion and mediates increased HCO3- reabsorption in terminal IMCD. The results further indicate that cHKA in vivo is sensitive to both SCH and ouabain.
- Subjects
POTASSIUM deficiency diseases; KIDNEYS; POTASSIUM metabolism; RNA metabolism; ADENOSINE triphosphatase; ANIMAL experimentation; BICARBONATE ions; BIOLOGICAL transport; CARDIAC glycosides; COLON (Anatomy); COMPARATIVE studies; GENES; HYPOKALEMIA; IMIDAZOLES; ISOENZYMES; KIDNEY tubules; RESEARCH methodology; MEDICAL cooperation; PERFUSION; POTASSIUM compounds; RATS; RESEARCH; RNA; STOMACH; EVALUATION research; IN vitro studies; PHARMACODYNAMICS
- Publication
Kidney International, 1998, Vol 54, Issue 4, p1233
- ISSN
0085-2538
- Publication type
journal article
- DOI
10.1046/j.1523-1755.1998.00105.x