Glycoprotein and protein production of isolated pig gastric mucosal cells were determined by the incorporation of N-acetyl-[¹⁴C]D-glucosamine ([¹⁴C]G1cNAc) and [³H]L-leucine ([³H]Leu) into acid-insoluble macromolecules (AIM). In four cell fractions (F1-F4), obtained by counterflow centrifugation, specific [¹⁴C]G1cNAc incorporation was greatest in the mucous cell-enriched F2. Tracer incorporation by F2 cells, proceeded lineraly up to 20 h, was inhibited by cycloheximide or incubation at 0 ° C, and enhanced by PGE₂ 1 μmol/l. Gel chromatography of released AIM revealed that PGE₂-stimulated [¹⁴C]GlcNAc incorporation was predominantly directed into high molecular weight (2 × 10⁶ daltons) glycoproteins, whereas [³H]Leu incorporation was mainly related to proteins of albumin-like molecular weight. We conclude that incorporation of [¹⁴C]G1cNAc by enriched pig gastric mucous cells (F2), further analyzed by gel chromatography, is a suitable probe to study the production of high molecular weight gastric mucous glycoproteins in vitro.

The production of glycoprotein and protein by isolated pig gastric non-parietal cells was measured by incorporation of N-acetyl-[¹⁴C]-D-glucosamine ([¹⁴C]GlcNAc) and [³H]-L-leucine ([³H]Leu), respectively, into acid insoluble material (AIM). Histamine enhanced incorporation of the tracers into cellular and released AIM in a concentration-dependent manner. The H₂ receptor antagonist ranitidine completely blocked the effects of histamine (100 μmol/l) on [³H]Leu incorporation into cellular and released AIM (IC50 37 and 32 μmol/l, respectively) but had no inhibitory effect on the 16,16-dimethylprostaglandin-E₂ – and forskolin-stimulated tracer incorporation. The H₁ receptor antagonist mepyramine did not inhibit the histamine effect. We conclude that histamine is a stimulant of protein, via H₂ receptors, and glycoprotein production of isolated pig gastric non-parietal cells.

The purpose of this study is

1 Glycoprotein and protein synthesis in and release from pig isolated, enriched gastric mucous cells were measured by the incorporation of N-acetyl-[j4C]-D-glucosamine and [3H]-L-leucine, respectively, into cellular and released acid precipitable material. 2 Histamine and activators of the adenosine 3' :5'-cyclic monophosphate (cyclic AMP) system maximally stimulated total protein and glycoprotein synthesis in and release from the cells at concentrations of histamine (10pM), forskolin (10-100pM), 3-isobutyl-1-methylxanthine (100pM), and dibutyryl cyclic AMP (1-3mM), respectively. In the presence of 3-isobutyl-1-methylxanthine (30pM) histamine stimulation was enhanced.3 As shown by gel chromatography, stimulation by histamine (100pM), forskolin (10uM), 3-isobutyl-1-methylxanthine (100pM) and dibutyryl cyclic AMP (1 mM) resulted in a release of high molecular weight ( 2 x 106 daltons) glycoproteins from the cells. The histamine H2-receptor antagonist, ranitidine (100uM), blocked the effect of histamine. 4 We conclude that cyclic AMP-dependent processes are involved in the regulation of protein and glycoprotein synthesis in and the release of high molecular weight (mucous) glycoproteins from pig gastric non-parietal cells and that histamine may be a physiological activator of this system.