Synthesis and secretion of glycoproteins by mucosa of rat gastric antrum in organ culture

Abstract

Measurement of gastric mucus production in vivo poses several problems. We therefore used organ culture of rat antrum to measure mucosal synthesis and secretion of glycoprotein. Tissue maintained good viability for 20 hr. Glycoprotein synthesis rate, assessed by incorporation of [3H]fucose and [3H]glucosamine, was constant during 20 hr. [3H]Fucose incorporation increased in proportion to increasing [fucose] in medium until the latter reached 10(-3) M, then the slope decreased. Cycloheximide abolished [3H]fucose incorporation into glycoprotein. Two methods for measuring secretion gave parallel results: prelabeled glycoprotein was secreted linearly, with 60% of pulse-labeled tissue glycoprotein appearing in medium in 20 hr. The data suggest that (1) antral mucous cells contain a high-concentration pool of endogenous fucose, but possibly only a small-capacity pool of preformed apoglycoprotein, (2) synthesis and secretion of glycoprotein can be successfully examined with organ culture, and (3) secretion in vitro occurs at a steady, slow rate.