Nutrient uptake into undifferentiated and differentiated HT-29 cells in culture

HT-29 human colon carcinoma cells in culture have many characteristics of enterocytes, and these cells have been used by others to study intestinal drug and nutrient transport and metabolism. When grown in glucose-containing medium, HT-29 cells are largely undifferentiated (HT-29(glu)) but when grown in the absence of glucose but in the presence of galactose (HT-29(gal)), the population of cells is mostly differentiated. This study was undertaken with HT-29(glu) and HT-29(gal) cells to study the uptake of palmitic acid (16:0), linoleic acid (18:2), and cholesterol. The relationship between concentration and uptake of 16:0, 18:2, and cholesterol was linear in HT-29(glu) and HT-29(gal) cells, with the relative values of the slopes of this relationship being 18:2 >> 16:0 >> cholesterol. The rates of uptake of these lipids were at least three times higher in HT-29(gal) than in HT-29(glu) cells. In HT-29(glu) cells, the relative rates of uptake of the sugars at 32 mM were D-glucose = galactose > fructose >> alpha-methylglucose. Uptake of these sugars was much greater in HT-29(gal) than in HT-29(glu) cells. When 100 mu M forskolin was added to the incubation medium for 7 days post-confluency, which stimulates the activity of adenylate cyclase and thereby increases the intracellular synthesis of cAMP, there was no effect on the uptake of the lipids or the sugars in either HT-29(glu) or HT-29(gal) cells. Thus, (i) differentiated HT-29(gal) cells transport larger amounts of lipids and sugars than do undifferentiated HT-29(glu) cells; (ii) forskolin has no effect on the uptake of lipids or sugars in these cells. This human cell culture system may be useful to study the in vitro transport of lipids, to establish the role of cell differentiation on these uptake processes, and to determine the potential role of selected intracellular signals.