Changes in [3H]galactose uptake in human colonic mucosa with carcinoma: an ultrastructural study.

As part of our investigation on glycoprotein synthesis in pre-malignant colonic epithelium, changes in the uptake of [3H]galactose were studied at the ultrastructural level. Normal control mucosa from rectal biopsies of patients with no known gastro-intestinal disease and mucosa adjacent to carcinoma ('transitional' mucosa) from specimens resected for colo-rectal cancel were compared. These tissues were incubated in TC 199 medium containing [3H]galactose for various intervals of time and for pulse labelling. Silver grain distribution was statistically analysed. The results showed a reduction in the incorporation of the galactose by 'transitional' mucosa. The uptake by this mucosa was less uniform than normal and showed considerable peaking in the endoplasmic reticulum of the goblet cells and in the Golgi of the absorptive cells, suggesting a blockage or alteration in glycoprotein synthesis. The differences were most marked in the middle crypt (the region of differentiation) and in the upper crypt (the region of maturation).