GLYCOPROTEIN SYNTHESIS IN HUMAN FETAL ESOPHAGUS, STOMACH, SMALL INTESTINE AND COLON

Abstract

Glycoproteins represent important components of the cell. No data are available concerning glycoprotein synthesis in esophagus (E), stomach (S), small intestine (SM) and colon (C) between 12 and 17 weeks' gestation. Explants of E, S, SM and C were cultured in serum-free Leibovitz L-15 medium at 37°C (J. Pediatr. Gastroenterol. Nutr. 1985; 4:893). Glycoprotein synthesis was evaluated by the incorporation of 3H-glucosamine (3H-Glu) into total protein during a 6 hour period and results expressed as DPM/pg protein. Explants were also processed for radioautography in order to visualize glycoprotein synthesis in the epithelial as well as in the non-epithelial compartments. The incorporation of 3H-Glu into total protein remained more or less constant between 12 and 17 weeks' gestation. The levels were similar in E, S and C and the SM exhibited the highest, 3H-Glu incorporation. Radioautographs illustrated newly formed glycoproteins in the epithelial and non-epithelial compartments of the different tissues of the gastrointestinal tract. Explants from E, S, SM and C were cultured during 5 days and glycoprotein synthesis evaluated at the beginning and the end of the culture (6 hours in presence of 10 μCi3H-Glu per ml). In all cases, glycoprotein synthesis drastically increased during the culture, the increases representing 196, 183, 66 and 337% respectively. In the SM, the increase of the total glycoprotein synthesis was reflected in part by an increment of inportant membrane glycoproteins, that is the brush border membrane hydrolytic enzymes. Such correlation was not found in the colon. Whether the increased synthesis observed in culture represents an accelerated maturation of fetal tissues remains to be elucidated. However, the present data strongly suggest the presence of glycoprotein synthesis inhibitor(s) in utero during human gastrointestinal tract development.