Rabbit esophageal cell cytoplasmic pH regulation: role of - antiport and -dependent transport systems

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 $$ cells per esophagus. Cells were attached to a glass cover slip that had been pretreated with rat-tail collagen, and pHi was measured continuously in a spectrofluorometer utilizing 2',7'-bis(2-carboxyethyl)-5(-6)- carboxyfluoroscein acetoxymethyl ester as a pH-sensitive fluorescent probe. The basal pHi of cells exposed to a $$-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% $$ and 28 mM $$ When H2 4,4'-diisothiocyanatostilbene- 2,2'-disulfonic acid (DIDS; 0.5 mM) was added, pHi was unchanged. However, addition of $$ M amiloride caused pHi to decrease to 7.29 ± 0.18 (P less than 0.01). When cells were acidified (pHi 6.3-7.0) using a(20 mM) pulse technique, pHi was rapidly restored toward neutrality in the presence of a $$-free external $$ concentration ([$$]o)-containing solution (pH units/min = 0.26 ± 0.12; n = 8). Alkalinization was completely blocked with $$ M amiloride. In the presence of $$ M amiloride, 28 mM $$, and 5% $$, acidified cells also alkalinized, although at a slower rate (0.11 ± 0.04 pH units/min; n = 16).(ABSTRACT TRUNCATED AT 250 WORDS)