AJP - Gastrointestinal and Liver Physiology, Vol 263, Issue 3 407-G413, Copyright © 1992 by American Physiological Society

ARTICLES

Rabbit esophageal cell cytoplasmic pH regulation: role of Na(+)-H+ antiport and Na(+)-dependent HCO3- transport systems

T. J. Layden, L. Schmidt, L. Agnone, P. Lisitza, J. Brewer and J. L. Goldstein
Department of Medicine, University of Illinois, Chicago.

Regulation of cytoplasmic pH (pHi) of esophageal cells assumes importance as these cells can be exposed to mucosally absorbed acid during gastroesophageal reflux episodes. In this study, we examined whether esophageal cells possess pHi transport systems. Esophageal cells were harvested utilizing a gentle trypsin technique that yielded 2-5 x 10(6) cells per esophagus. Cells were attached to a glass cover slip that had been pretreated with rat-tail collagen, and pHi was measured continuously in a spectrofluorometer utilizing 2',7'-bis(2-carboxyethyl)-5(-6)- carboxyfluoroscein acetoxymethyl ester as a pH-sensitive fluorescent probe. The basal pHi of cells exposed to a Na(+)-containing solution averaged 7.52 +/- 0.20 (n = 6). The pHi declined slightly but not significantly to 7.46 +/- 0.12 with the addition of 5% CO2 and 28 mM NaHCO3. When H2 4,4'-diisothiocyanatostilbene- 2,2'-disulfonic acid (DIDS; 0.5 mM) was added, pHi was unchanged. However, addition of 10(-4) M amiloride caused pHi to decrease to 7.29 +/- 0.18 (P less than 0.01). When cells were acidified (pHi 6.3-7.0) using a NH4Cl (20 mM) pulse technique, pHi was rapidly restored toward neutrality in the presence of a HCO3(-)-free external Na+ concentration ([Na+]o)-containing solution (pH units/min = 0.26 +/- 0.12; n = 8). Alkalinization was completely blocked with 10(-4) M amiloride. In the presence of 10(-4) M amiloride, 28 mM NaHCO3, and 5% CO2, acidified cells also alkalinized, although at a slower rate (0.11 +/- 0.04 pH units/min; n = 16).(ABSTRACT TRUNCATED AT 250 WORDS)

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