Ethanol induces volume changes and gap junction closure via intracellular Ca2+ signalling pathway in cultured rabbit gastric epithelial cells.

BACKGROUND: Ethanol is a well-established 'barrier breaker' in gastric mucosa, but its effects at cellular level remain to be detailed.
METHODS: Gastric epithelial cells were isolated from rabbits and cultured to monolayers. Intracellular calcium was measured spectrofluorometrically with fura-2. The patency of gap junctions was assessed by photobleaching a small area of 5-carboxyfluorescein loaded monolayer and measuring recovery of fluorescence. For cell volume measurements the change in fluorescence intensity was followed in calcein-loaded monolayers with a confocal microscope.
RESULTS: Intracellular calcium concentration was increased from 65 +/- 9 to 140 +/- 17 nM; recovery of fluorescence signal after photobleaching was diminished from 53% +/- 11% to 9% +/- 3%; and cell volume was decreased significantly after 10 min exposure to 5% (vol/vol) ethanol. This volume decrease was prevented with serosal application of the potassium channel blocker, quinine, or by blocking the intracellular calcium signalling pathway with the intracellular calcium-chelating agent BAPTA. This suggests that luminal ethanol opens the basolateral calcium-dependent potassium selective channels via calcium signalling pathway, with resultant shrinkage of the cell.
CONCLUSION: Intracellular calcium concentration is increased, gap junctions are closed and cell volume is decreased after exposure to 5% ethanol. Since gap junctions are known to be calcium gated, it is likely that their closure is secondary to the elevated cytosolic calcium in ethanol injured cells. This may have a protective function by limiting intercellular spread of impending cell injury. The opening of the basolateral potassium channel probably underlies the ethanol-induced cell shrinkage and might contribute to the ethanol-provoked epithelial damage.