title: HCO3- secretion in mitochondria-rich cells is linked to an H+-ATPase.
abstract: Turtle bladder mitochondria-rich (MR) cells secrete H+ by an ATP-dependent process. MR cells also secrete HCO3- by an energy-requiring, Cl- -dependent process that may depend on a serosal H+-ATPase. To determine whether HCO3- is linked to an H+-ATPase, O2 consumption was assessed in MR and granular (G) cells exposed to H+ and HCO3- transport inhibitors alone and also with an H+-ATPase inhibitor. MR and G cells were separated by Ficoll density-gradient centrifugation and treated with ouabain and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) to maximally inhibit Na+ and luminal H+ transport. O2 consumption was measured before and after cells were additionally treated with 10 microM N-ethylmaleimide (NEM), an inhibitor of nonmitochondrial H+-ATPase. O2 consumption of MR cells fell after treatment with NEM (delta = 8.64 +/- 2.35 microliters O2.h-1.mg protein-1, P less than 0.025, n = 5). There was no significant difference in G cells similarly treated (delta = 1.61 +/- 0.62 microliters O2.h-1.mg protein-1, P greater than 0.05, n = 5). Because luminal H+ secretion is nearly abolished after treatment with SITS, the decline in O2 consumption of 44.4 +/- 7.11% after addition of NEM is probably due to inhibition of other non-mitochondrial H+-ATPases. In the intact bladder, HCO3- secretion was reduced by 35.1% after serosal application of NEM. Furthermore, in SITS-treated MR and G cells, ATP levels as measured by the luciferin-luciferase assay method were not appreciably different in the presence or absence of NEM.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, C. J. Zablocki Veterans Administration Medical Center, Milwaukee, Wisconsin.
authors.forename: C
authors.initials: C
authors.lastname: Fritsche
authors.forename: J H
authors.initials: JH
authors.lastname: Schwartz
authors.forename: R R
authors.initials: RR
authors.lastname: Heinen
authors.forename: R
authors.initials: R
authors.lastname: Tietz
authors.forename: J G
authors.initials: JG
authors.lastname: Kleinman
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D005033:Ethylmaleimide / Q000494:pharmacology; D006098:Granulocytes / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D010092:Oximetry; D010101:Oxygen Consumption / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D014426:Turtles; D001743:Urinary Bladder / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D006859:Hydrogen; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D005033:Ethylmaleimide