title: K depletion stimulates in vivo HCO3 reabsorption in surviving rat distal tubules.
abstract: To evaluate whether K depletion enhances in vivo bicarbonate reabsorption (JtCO2) in surviving distal tubules (DT), we compared DT JtCO2 in five-sixths nephrectomized rats (Nx) with and without dietary K depletion (Nx-K). Furthermore, to identify possible mechanisms of increased JtCO2, we perfused inhibitors of proton secretion in both Nx and Nx-K rats. JtCO2 (102 +/- 8 pmol.min-1.mm-1) was significantly increased in Nx-K vs. Nx rats (65 +/- 7 pmol.min-1.mm-1, P < 0.05) but unaffected by 10(-6) M losartan perfusion (94 +/- 6 pmol.min-1.mm-1, P = not significant). Although 10(-5) M Sch-28080 also had no significant effect, 5 x 10(-9) M concanamycin A perfusion significantly decreased JtCO2 in Nx-K rats to 65 +/- 8 pmol.min-1. mm-1 (P < 0.05). Morphometric evaluation and H(+)-ATPase immunogold labeling of Nx-K A-type intercalated cells revealed cellular hypertrophy, elaborated apical microplicae, and enhanced H(+)-ATPase apical polarization. Accordingly, these combined studies confirm that K depletion enhances JtCO2 in surviving DT by stimulating H(+)-ATPase activity, independent of the AT1 receptor.
authors.affiliation: Department of Medicine, University of Ottawa, Ontario, Canada.
authors.forename: D Z
authors.initials: DZ
authors.lastname: Levine
authors.forename: M
authors.initials: M
authors.lastname: Iacovitti
authors.forename: S
authors.initials: S
authors.lastname: Buckman
authors.forename: B
authors.initials: B
authors.lastname: Luck
authors.forename: M T
authors.initials: MT
authors.lastname: Hincke
authors.forename: K D
authors.initials: KD
authors.lastname: Burns
authors.forename: J N
authors.initials: JN
authors.lastname: Fryer
mesh_terms: D000042:Absorption / Q000502:physiology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism*; D015153:Blotting, Western; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D007120:Immunochemistry; D007150:Immunohistochemistry; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D018942:Macrolides; D008297:Male; D008854:Microscopy, Electron; D009392:Nephrectomy; D011191:Potassium Deficiency / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013270:Stomach / Q000201:enzymology
chemical_list: D000900:Anti-Bacterial Agents; D001639:Bicarbonates; D004791:Enzyme Inhibitors; D007093:Imidazoles; D018942:Macrolides; C035235:Sch 28080; C036978:concanamycin A; D017506:H(+)-K(+)-Exchanging ATPase