Rabbit esophageal cell cytoplasmic pH regulation: role ofNa+-H+antiport andH+-dependentHCO3-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 yielded2-5×106cells 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.H+The basal pHi of cells exposed to aH+-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%CO2and 28 mMNaHCO3When H2 4,4'-diisothiocyanatostilbene- 2,2'-disulfonic acid (DIDS; 0.5 mM) was added, pHi was unchanged. However, addition of10-6M 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 aa2+b2=c2(20 mM) pulse technique, pHi was rapidly restored toward neutrality in the presence of aHCO3--free externalNa+concentration ([Na+]o)-containing solution (pH units/min = 0.26 ± 0.12; n = 8). Alkalinization was completely blocked with10-6M amiloride. In the presence of10-6M amiloride, 28 mMNaHCO3, 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)
Layden
T J
TJ
Department of Medicine, University of Illinois, Chicago.
Schmidt
L
L
Agnone
L
L
Lisitza
P
P
Brewer
J
J
Goldstein
J L
JL
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000502:physiology*; D002448:Cell Adhesion; D003584:Cytological Techniques; D003593:Cytoplasm / Q000378:metabolism*; D004947:Esophagus / Q000166:cytology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D011817:Rabbits; D012964:Sodium / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers
D001639:Bicarbonates; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium