Differentiation of glycoprotein synthesis in fetal rat colon.

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Abstract
Glycoprotein synthesis in fetal rat colon was studied during the last 4 days of gestation as the mucosa matures from a primitive structure to one that resembles adult colon. After i.v. injection of precursor surgars into pregnant mothers, there was an increase with advancing fetal age in incorporation of [3H]galactose and [3H]fucose, but not [3H]glucosamine, into colonic glycoproteins. Radioautography revealed newly synthesized glycoprotein distributed diffusely throughout the cytoplasm of of epithelial cells 4 days before birth with little progression with tieme of label towards the apical cell surface. Two days later, intracellular migration of newly synthesized glycoprotein changed to the adult pattern with initial sugar incorporation in the supranuclear region followed by migration of labeled glycoproteins toward the apical surface in absorptive and goblet cells by 5 h. [3H]glucosamine was incorporated effectively by absorptive and goblet cells, whereas [3H]galactose was incorporated selectively by goblet cells. Glucosamine and galactose were incorporated into high MW and low MW glycoprotein fractions as determined by gel filtration of cytosol glycoproteins. The cellular differentiation of rat colon during the last 4 gestational days was accompanied by increased glycoprotein synthesis and development of the adult pattern of intracellular migration of newly synthesized glycoproteins.