Linked Life Data

2553856

Source:http://linkedlifedata.com/resource/pubmed/id/2553856

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1989-11-28
pubmed:abstractText
Intracellular microelectrode techniques and intracellular pH (pHi) measurements using the fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) were employed to characterize an electrogenic bicarbonate transport mechanism at the apical membrane of the frog retinal pigment epithelium (RPE). Reductions in apical concentrations of both [HCO3]o (at constant Pco2 or pHo) or [Na]o caused rapid depolarization of the apical membrane potential (Vap). Both of these voltage responses were inhibited when the concentration of the other ion was reduced or when 1 mM diisothiocyano-2-2 disulfonic acid stilbene (DIDS) was present in the apical bath. Reductions in apical [HCO3]o or [Na]o also produced a rapid acidification of the cell interior that was inhibited by apical DIDS. Elevating pHi at constant Pco2 (and consequently [HCO3]i) by the addition of apical NH4 (20 mM) produced an immediate depolarization of Vap. This response was much smaller when either apical [HCO3]o or [Na]o was reduced or when DIDS was added apically. These results strongly suggest the presence of an electrogenic NaHCO3 cotransporter at the apical membrane. Apical DIDS rapidly depolarized Vap by 2-3 mV and decreased pHi (and [HCO3]i), indicating that the transporter moves NaHCO3 and net negative charge into the cell. The voltage dependence of the transporter was assessed by altering Vap with transepithelial current and then measuring the DIDS-induced change in Vap. Depolarization of Vap increased the magnitude of the DIDS-induced depolarization, whereas hyperpolarization decreased it. Hyperpolarizing Vap beyond -114 mV caused the DIDS-induced voltage change to reverse direction. Based on this reversal potential, we calculate that the stoichiometry of the transporter is 1.6-2.4 (HCO3/Na).
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0022-1295
pubmed:author
pubmed:issnType
Print
pubmed:volume
94
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
125-50
pubmed:dateRevised
2008-11-20
pubmed:meshHeading
pubmed-meshheading:2553856-4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid, pubmed-meshheading:2553856-4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid, pubmed-meshheading:2553856-Animals, pubmed-meshheading:2553856-Bicarbonates, pubmed-meshheading:2553856-Biological Transport, pubmed-meshheading:2553856-Electric Conductivity, pubmed-meshheading:2553856-Female, pubmed-meshheading:2553856-Fluoresceins, pubmed-meshheading:2553856-Hydrogen-Ion Concentration, pubmed-meshheading:2553856-Isoelectric Point, pubmed-meshheading:2553856-Male, pubmed-meshheading:2553856-Membrane Potentials, pubmed-meshheading:2553856-Microelectrodes, pubmed-meshheading:2553856-Pigment Epithelium of Eye, pubmed-meshheading:2553856-Quaternary Ammonium Compounds, pubmed-meshheading:2553856-Rana catesbeiana, pubmed-meshheading:2553856-Sodium, pubmed-meshheading:2553856-Sodium Bicarbonate
pubmed:year
1989
pubmed:articleTitle
Apical electrogenic NaHCO3 cotransport. A mechanism for HCO3 absorption across the retinal pigment epithelium.
pubmed:affiliation
School of Optometry, University of California, Berkeley 94720.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.