Aim/Background We previously reported that esophageal epithelium (EE), both stratified squamous (SS) and Barrett's (BE), from pinch biopsies could be mounted and studied electrically in mini-Ussing chambers and showed that they have distinctly different electrical parameters, including significantly different short-circuit currents (Isc).
Methods To further elucidate the nature of the differences in Isc in these two types of EE, jumbo biopsies were obtained from subjects with normal SS or subjects with BE and mounted in mini-Ussing chambers (Lucite rings of aperture diameter 2 mm) for measurement of potential difference, Isc and calculation of total electrical resistance while bathed in normal Ringer's solution at 37°C, pH 7.4, gassed with 95%O2/5%CO2. Following basal recordings of Isc, tissues were exposed to either Cl-free Ringer's or HCO3-free HEPES Ringer bubbled with O2. To validate that the tissues under study were viable and that the Isc was not the result of severe edge damage, only tissues in which serosal ouabain, 1 mM, reduced Isc by ≥ 89% at the end of the experiments were used.
Results (Means ± SEM). For ESSE (n = 18) vs BSCE (n = 6): basal PD was -1.2 ± 0.2 vs -3.6 ± 2 mV; Isc was 4.2 ± 0.9 vs 42 ± 19 μAmps/cm2 and RT was 360 ± 42 vs 68 ± 10 ohm.cm2. Notably basal Isc and RT were significantly different for SS vs BE (p < .05), and this was consistent with differences reported in vivo for esophageal PD of SS and BE. Removal of Cl from luminal and serosal bathing solutions reduced Isc a similar percentage for both SS and BE ˜ 5-10% of Isc; however, the magnitudes of the decline in Isc were significantly different with Cl-free in SS falling 0.9 ± 0.4 μAmps/cm2 and in BE falling 16.5 ± 8.2 μAmps/cm2. Similarly the percent declines in Isc with HCO3-free were no different for SS and BE (˜ 10-25%); however, the magnitude of the declines were significantly different, with SS falling 0.9 ± 0.4 μAmps/cm2 and with BE falling 5.7 ± 3.0 μAmps/cm2.
Conclusions Human SS epithelium and BE have markedly different capacities for active ion transport, BE exhibiting a ten-fold greater current. The higher current in BE is generated by active Cl secretion (˜ 38% of Isc) and active HCO3 secretion (˜ 16% of Isc). The active HCO3 secretion is notable for its ability to contribute to protection of BE against acid injury as part of the pre-epithelial buffer zone.
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