We examined the effects of sucralfate on the secretion and synthesis of mucus by cultured rabbit gastric mucosal cells, and the underlying intracellular mechanism. Treatment of mucosal cells with sucralfate (>0.5 mg/ml) for 4 and 8 hr caused a significant increase in the inositol triphosphate (IP3) content in the cells. Neomycin (a phospholipase C inhibitor) at 1 mM markedly inhibited the sucralfate-induced increases in both the IP3 content and mucus secretion and synthesis. Neither 10 nM staurosporine, 1 mM H-7 (protein kinase C inhibitors), nor 5 microM indomethacin (a cyclooxygenase inhibitor) affected the stimulatory effects of sucralfate on mucus secretion and synthesis, but 10 microM TMB-8 (an antagonist of intracellular Ca2+ mobilization)abolished its effects. Taken together, these results demonstrate that sucralfate acts directly an gastric mucosal cells, inducing increases in mucus secretion and synthesis, and that sucralfate causes an increase in the IP3 content, probably through activation of phospholipase C, and the subsequent IP3-elicited Ca2+ mobilization may be involved in the stimulatory effects of sucralfate.