EFFECTS OF CALCIUM-MODIFYING AGENTS ON INTEGRITY OF RABBIT ISOLATED GASTRIC-MUCOSAL CELLS

The effects of Ca2+-modifying agents on the disruption of gastric isolated mucosal cells from the rabbit have been examined. Fundic mucosal cells were isolated and enriched by centrifugal elutriation, with cellular viability and disruption being assessed by trypan blue dye exclusion and by the release of lysosomal enzymes. The Ca2+ ionophore A23187 (3.125-50-mu-M) induced a concentration-dependent increase in enzyme marker release and decreased dye exclusion from the cells. Ionophore-induced enzyme release was reduced by removal of Ca2+ or by incubation with EDTA. Cells from the medium-sized fraction were found to be more sensitive to damage by A23187 than were larger-diameter cells. Enzyme release from these cells was also induced by the Ca2+-channel activator BAY K 8644 (1.5-mu-M). The Ca2+-channel antagonists, nifedipine, verapamil, and diltiazem (1-mu-M), abolished enzyme release in response to BAY K 8644 (1.5-mu-M) but did not affect A23187 (25-mu-M)-induced responses. Ethanol (5 and 8%) also induced a concentration-dependent increase in enzyme release and decrease in dye exclusion, but this effect was not dependent on the external Ca2+ concentration. However, threshold concentrations of A23187 (1.56-mu-M) substantially potentiated the cell damage induced by ethanol (5 or 8%), and this synergism was dependent on external Ca2+. These data suggest that agents that produce an inappropriate Ca2+ flux can disrupt or augment disruption of gastric mucosal cells and thus Ca2+ homeostasis is essential for maintenance of mucosal cell integrity.