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 int estinal drug and nutrient transport and metabolism. When grown in gluc ose-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 differentia ted. 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 c holesterol. 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 l east 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 wer e D-glucose = galactose > fructose >> alpha-methylglucose. Uptake of t hese sugars was much greater in HT-29(gal) than in HT-29(glu) cells. W hen 100 mu M forskolin was added to the incubation medium for 7 days p ost-confluency, which stimulates the activity of adenylate cyclase and thereby increases the intracellular synthesis of cAMP, there was no e ffect on the uptake of the lipids or the sugars in either HT-29(glu) o r HT-29(gal) cells. Thus, (i) differentiated HT-29(gal) cells transpor t larger amounts of lipids and sugars than do undifferentiated HT-29(g lu) cells; (ii) forskolin has no effect on the uptake of lipids or sug ars in these cells. This human cell culture system may be useful to st udy the in vitro transport of lipids, to establish the role of cell di fferentiation on these uptake processes, and to determine the potentia l role of selected intracellular signals.