Parallel pathways for ion transport across rat gastric mucosa: effect of ethanol.

Transmural fluxes of 22Na or 36Cl across the isolated rat gastric mucosa were measured simultaneously with [3H]mannitol in an attempt to separate transmural ionic movement into cellular and noncellular components. The relationships between mannitol flux and the fluxes of Na and Cl are characteristic of simple diffusion, suggesting that mannitol traverses the isolated epithelium largely via noncellular pathways. The total tissue conductance can be described as the sum of two components, one of which is highly correlated with the transmural mannitol flux and presumably represents the conductance of a noncellular leak path. The cellular components of the mucosa-to-serosa Na flux and of both Cl fluxes are highly correlated with the short-circuit current. Exposure of the mucosal surface of the epithelium to 4% ethanol reduces the short-circuit current and increases the electrical conductance. Ethanol inhibits the active transport of Na and Cl and increases the apparent permeability of noncellular pathways for transmural ionic diffusion.