Synthesis and release of phosphatidylcholine by isolated porcine gastric mucous cells in primary culture.

Phosphatidylcholine (PC) is the major phospholipid of the hydrophobic gastric mucosal barrier and is chiefly released from mucous cells into the gastric mucus. Whereas the mucosa contains highly unsaturated PC, gastric mucus predominantly contains palmitoyl-oleoyl-PC and palmitoyl-linoleoyl-PC, indicating a selective release of these PC species into the gastric lumen. In order to understand gastric PC metabolism, we investigated synthesis and release of PC in cultivated porcine gastric mucous cells, using dual labelling with [methyl-3H]-choline and [1-14C]-palmitate, in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA), indomethacin and prostaglandin E2 (PGE2). Linear incorporation of [methyl-3H]-choline and [1-14C]-palmitate into PC was achieved for at least 8h. In contrast to type II pneumocytes TPA increased PC synthesis in gastric mucous cells but not its release. Indomethacin did not influence PC synthesis, but it decreased the release of newly synthesized PC. PGE2 antagonized the effect of indomethacin on PC release. We conclude that PC release by isolated porcine gastric mucous cells is regulated in a manner different from type II pneumocytes. PC release is impaired by indomethacin and this impairment is restored by PGE2.