HCl-induced cell edema in primary cultured rabbit esophageal epithelium.

BACKGROUND & AIMS: In a prior study, esophageal epithelial cells within intact epithelium were observed to swell after exposure to low extracellular pH (pHo) caused by activation of a bumetanide-sensitive NaK2Cl cotransporter. Because these results were obtained by correlation of tissue wet-weight gain with morphological evidence of cell swelling, another method was selected to confirm and extend these findings.

METHODS

Primary cultured rabbit esophageal cells were loaded with the fluorescent dye 2'-7'-bis(carboxyethyl)-5,6-carboxyfluorescein so that changes in intracellular pH (pHi) and cell volume could be simultaneously monitored by microfluorimetry.

RESULTS

Cells exposed to low pHo in both bicarbonate-free and bicarbonate-containing buffers produced a decline in pHi to as low as 6.5, but this occurred without change in volume. However, when pHo was lowered to < or = 2, pHi declined to <6.5 and volume increased by 25% in 3 minutes. Removal of Na+, K+, or Cl- or adding bumetanide inhibited acid-induced swelling. Also, swelling was inhibited when cells were acidified in Ca2+-free media and eliminated by adding 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid to Ca2+-free media.

CONCLUSIONS

Esophageal cells swell when low pHo reduces pHi to <6.5. At pHi <6.5, swelling occurs through excess osmolyte (and consequently water) uptake via a bumetanide-sensitive NaK2Cl cotransporter. Activation of this enzyme at low pHi seems to be mediated by increases in cell Ca2+.