Cyclic GMP-dependent cytoprotection against ethanol-induced damage in rabbit isolated gastric parietal cells.

Prostaglandin E2 stimulates a nitric oxide/cyclic GMP (NO/cGMP) pathway which activates basolateral Cl- channels in rabbit gastric parietal cells. We examined whether the NO/cGMP pathway protects parietal cells from ethanol (EtOH)-induced cytotoxicity, using a parietal cell-rich suspension purified from rabbit gastric mucosa. Cytotoxicity was assayed by measuring the release of a fluorescent dye from the cells. N2,O2-dibutyryl guanosine 3',5'-cyclic monophosphate (DBcGMP) showed a concentration-dependent protective effect against EtOH-induced cytotoxicity. The half-maximal effect of DBcGMP was observed at 24 microM. DBcGMP in a concentration-dependent manner opened the basolateral Cl- channels of parietal cells, the EC50 value being 44 microM. The EtOH-induced cytotoxicity decreased as the Cl- concentration of medium decreased. A 30-s treatment with 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), an inhibitor of the Cl- channel, had a cytotoxic effect which was not prevented by pre-incubation with DBcGMP. The cytotoxic effects of EtOH and NPPB were additive and the NPPB effects did not depend on the medium Cl- concentration. The present study showed that cGMP protects the gastric parietal cell from EtOH-induced cytotoxicity, and this cytoprotection is related to basolateral Cl- channel activity in the plasma membrane via an unknown mechanism(s).