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Am J Physiol Gastrointest Liver Physiol 257: G732-G740, 1989;
0193-1857/89 $5.00
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AJP - Gastrointestinal and Liver Physiology, Vol 257, Issue 5 732-G740, Copyright © 1989 by American Physiological Society

ARTICLES

Intracellular pH regulation in IEC-6 cells, a cryptlike intestinal cell line

E. Wenzl, M. D. Sjaastad, W. H. Weintraub and T. E. Machen
Department of Molecular and Cell Biology, University of California, Berkeley 94720.

Regulation of intracellular pH, pHi, was studied using microspectrofluorimetry of the pH-sensitive, fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein in the rat intestinal crypt cell line, IEC-6. In N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered solutions with pHi 7.25, treatment with a pulse of NH4Cl caused cells to acidify and then recover to control level. Because recovery was Na dependent, blocked by 1 mM amiloride, and unaffected by the presence and absence of Cl, it was likely because of a Na+-H+ exchanger. Cells were also acid loaded by changing from HEPES to HCO3-CO2-buffered solutions. pHi again recovered, but 1 mM amiloride reduced the rate of H+ efflux by only 47%. This HCO3-dependent, amiloride-insensitive H efflux required Na+ but not Cl- and was completely blocked by 200 microM [H2] 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). We conclude that a Na+-HCO3- cotransporter was operative. Cl-free solutions caused pHi to increase from 7.19 to 7.41; this effect required the presence of exogenous HCO3-CO2 but not Na and was blocked by 200 microM [H2]DIDS. A Cl- -HCO3- exchanger is the most likely explanation for these data. All the pHi regulatory mechanisms are operative in NaCl-HCO3-CO2-buffered solutions. The Na+-H+ and Na+-HCO3- mechanisms are acid extruders, whereas the Cl- -HCO3- exchanger is an acid loader. These transporters may be important for generating HCO3 secretion by intestinal crypt cells.


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