The consequences of injected 2‐deoxy‐d‐galactose on the biosynthesis of glycoproteins have been studied in rat liver and Morris hepatoma 9121. The incorporation of 2‐deoxy‐d‐galactose into glycoprotein (a), the Subsequent glycosylation with l‐fucose and N‐acetylneuraminic acid (b), and the impairment of the rat uracil nucleotide levels (c) have been determined.

a) The rates of uptake and incorporation of 2‐deoxy‐d‐galactose into glycoprotein were evaluated in various tissues of the rat. When compared to d‐galactose they were found to be decreased in most tissues, especially in liver and hepatoma. After labeling with 2‐deoxy‐d‐galactose in vivo the identification of the label in glycoprotein fractions mainly yielded 2‐deoxy‐d‐galactose and no 2‐deoxy‐d‐glucose. Autoradiographic analysis of plasma membranes and serum, using polyacrylamide gel electrophoresis for separation, indicates the presence of the same bands with either 2‐deoxy‐d‐galactose or with d‐galactose as the label.

b) 1 h after a single dose of 200 mg 2‐deoxy‐d‐galactose/kg body weight a 25–50% decrease of the subsequent l‐fucose incorporation into the acid‐precipitable fraction of serum, liver and hepatoma was observed compared to untreated controls. Time‐courses and dose‐dependences of the inhibitory effect were obtained in these tissues including the hepatoma plasma membrane fraction. A simultaneous increase in the acid‐soluble l‐fucose concentration was found in both liver and serum. The specificity of this effect was shown by an unchanged incorporation of N‐acetyl‐d‐mannosamine as the precursor of N‐acetylneuraminic acid. Protein synthesis, as measured by l‐leucine incorporation, was also not impaired after 2‐deoxy‐d‐galactose treatment. Injection of 2‐dcoxy‐d‐galactose as followed by labeling with l‐[¹⁴C] fucose in vivo and autoradiographic analysis of plasma membrane, cytosol and serum lead to shifts of bands. In contrast, only minimal changes were seen in hepatoma tissue.

c) Uracil 5′‐nucleotide concentrations were determined in livers and tumors of ACI rats bearing the Morris hepatoma 9121. 1 h after the injection of 200 mg 2‐deoxy‐d‐galactose/kg body weight the levels of UDP‐glucose and UDP‐galactose in host liver were depressed by 50%. However, no fall was found in hepatoma tissue. Supplementation experiments with uridine showed that the decreased concentrations of uracil nucleotides are not responsible for the reduced l‐fucose incorporation into glycoprotein.

From the data presented it can be concluded that the incorporation of 2‐deoxy‐d‐galactose specifically modifies the of oligosaccharide moiety of glycoprotein in vivo. By blocking the C‐2 for the attachment of l‐fucose this d‐galactose analog may serve as an experimental tool for studying the significance of terminal l‐fucose in secreted and membrane‐bound glycoproteins.