title: Mechanisms of H+ secretion by inner medullary collecting duct cells.
abstract: Inner medullary collecting duct cells were isolated from rat papillae and grown to confluence on cover slips. H+ secretion was estimated by intracellular pH (pHi) changes measured with the fluorescent probe 2,7-biscarboxyethyl-5(6)-carboxyfluorescein. In buffered NaCl, pHi was 7.14 +/- 0.04 (n = 78). After acidification about 40% of monolayers exhibited Na+-independent alkalinization. In 5 mM glucose, cell alkalinization occurred at a rate of 47 +/- 4 nM H+/min. However, cell alkalinization did not occur in the presence of 2-deoxy-D-glucose (5-15 mM), iodoacetate (5 mM), or KCN (5 mM). All monolayers tested exhibited amiloride-inhibitable Na+-dependent cell alkalinization that appeared to be a first-order kinetic process; Km [Na+] was approximately 52 mM and Vmax was approximately 250 nM [H+]/min. At a constant extracellular [Na+] (110 mM), Na+-dependent H+ efflux was a first-order function of pHi; Km for intracellular [H+] = 321 nM and Vmax = 182 nM H+/min. The data are consistent with the presence of a primary active H+ pump and a secondary active Na+ exchanger. The metabolic energy for the active H+ pump can be provided by glycolysis and oxidative phosphorylation.
authors.affiliation: Thorndike Memorial Laboratory, Boston City Hospital, Massachusetts.
authors.forename: A M
authors.initials: AM
authors.lastname: Selvaggio
authors.forename: J H
authors.initials: JH
authors.lastname: Schwartz
authors.forename: H H
authors.initials: HH
authors.lastname: Bengele
authors.forename: F D
authors.initials: FD
authors.lastname: Gordon
authors.forename: E A
authors.initials: EA
authors.lastname: Alexander
mesh_terms: D000468:Alkalies / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D002478:Cells, Cultured; D004072:Digitonin; D004734:Energy Metabolism; D005452:Fluoresceins; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007679:Kidney Medulla; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000494:pharmacology
chemical_list: D000468:Alkalies; D005452:Fluoresceins; D007477:Ions; D006859:Hydrogen; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium; D004072:Digitonin