EFFECT OF WATER IMMERSION STRESS ON THE BIOSYNTHESIS OF RAT GASTRIC GLYCOPROTEINS WITH OR WITHOUT SULFATE

Abstract

The biosynthesis of rat gastric glycoproteins with or without sulfate was investigated in rats subjected to restraint and water immersion stress. Studies were carried out in vitro in rat glandular stomach using ³H-glucosamine and ³⁵S-sulfate. Labeled glycoproteins were extracted with 2% Triton X-100 and fractionated on Bio Gel A-1.5 m. Radioactivity incorporated into glycoproteins was estimated in the tissue as well as in the medium. The incorporation of ³H-glucosamine into the tissue was unchanged during the experimental period, while the release of ³H-labeled glycoproteins into the medium was markedly increased at 12 h after the onset of stress. The incorporation of ³⁵S-sulfate into the tissue was decreased at 6 h and increased at 12 h. The release of ³⁵S-labeled glycoproteins into the medium was not changed significantly. However, the change in the total radioactivity (tissue plus medium) of ³H was similar to that of ³⁵S. These results suggest that the remarkable increase in the biosynthesis of glycoproteins and sulfated glycoproteins was closely related to reinforcement of defensive response. Furchermore, we investigated the effect of anti-ulcer agents on the biosynthesis of mucus glycoproteins. Cimetidine and atropine decreased the incorporation of radioactive precursors and the release of labeled glycoproteins into the incubation medium in vitro. AAHA (N-(N-acetly-β-alanyl)-L-histidine aluminum complex) and sofalcone (SU-88; 2-carboxymethoxy-4, 4'-bis (3-methyl-2-butenyloxy) chalcone) increased the incorporation of radioactive precursors and the release of labeled glycoproteins into the medium. These observations indicate that anti-ulcer agents having different modes of action show different effects on the glycoprotein biosynthesis.