Extraction of glycoproteins during tissue preparation for electron microscopy

The extraction of glycoproteins labelled with 3H or 14C precursors: fucose and glucosamine, has been compared during processing of rat liver for transmission electron microscopy. Using 14C labelled fucose, approximately 6% of labelled macromolecules were extracted during processing including 3% during glutaraldehyde fixation, 1% during post-fixation and 2% during dehydration. Greater extraction (8%) occurs with glucosamine as a precursor, which may be attributed to hydrolysis of the more labile sialic acid residues of the glycoprotein molecules. Tritium labelled glycoproteins were more susceptible to extraction than 14C-labelled glycoproteins. The extraction of 3H-labelled glycoproteins as measured by liquid scintillation counting may prove difficult to interpret owing to the quenching from processing solutions.