Proximal duodenal enterocyte transport: evidence for Na(+)-H+ and Cl(-)-HCO3- exchange and NaHCO3 cotransport

Am J Physiol. 1993 Oct;265(4 Pt 1):G677-85. doi: 10.1152/ajpgi.1993.265.4.G677.

Abstract

The duodenum, in contrast to the jejunum, actively secretes HCO3- at a high rate, a process that protects the mucosa from acid/peptic injury. Our purpose was to define the mechanisms involved in HCO3- transport by studying the acid-base transport processes in isolated duodenal enterocytes. Individual rat duodenocytes, isolated by a combination of Ca2+ chelation and collagenase, attached to a collagen matrix were loaded with the pH-sensitive fluoroprobe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM), and intracellular pH was monitored by microfluorospectrophotometry. To identify Na(+)-H+ transport, cells in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid 1) were pulsed with NH4Cl (40 mM) in the absence and presence of amiloride and 2) were removed of Na+. To examine Cl(-)-HCO3- exchange, Cl- was removed from Ringer-HCO3- superfusate in the presence and absence of dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (H2DIDS). The NaHCO3 cotransporter was studied by addition and subtraction of Na+ to amiloride-treated and Cl(-)-depleted enterocytes perfused with Na(+)- and Cl(-)-free Ringer-HCO3- buffer with and without H2DIDS. Mammalian duodenocytes contain at least three acid-base transporters: an amiloride-sensitive Na(+)-H+ exchanger that extrudes acid, a DIDS-sensitive Cl(-)-HCO3- exchanger that extrudes base, and a NaHCO3 cotransporter, also DIDS sensitive, that functions as a base loader. These acid-base transporters likely play a key role in duodenal mucosal HCO3- secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / analogs & derivatives
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Amiloride / pharmacology
  • Animals
  • Antiporters / metabolism*
  • Biological Transport / drug effects
  • Carrier Proteins / metabolism*
  • Cell Separation
  • Cell Survival
  • Chloride-Bicarbonate Antiporters
  • Duodenum / cytology
  • Duodenum / metabolism*
  • Hydrogen-Ion Concentration
  • Male
  • Rats
  • Rats, Sprague-Dawley
  • Sodium-Bicarbonate Symporters
  • Sodium-Hydrogen Exchangers / metabolism*

Substances

  • Antiporters
  • Carrier Proteins
  • Chloride-Bicarbonate Antiporters
  • Sodium-Bicarbonate Symporters
  • Sodium-Hydrogen Exchangers
  • dihydro-DIDS
  • Amiloride
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid