Folic acid uptake characteristics of a human colon carcinoma cell line, Caco-2. A newly-described cellular model for small intestinal epithelium.

To investigate a newly described model for differentiated small intestinal function, folic acid uptake characteristics were examined in the human colon carcinoma cell line, Caco-2. Monolayers of this cell line spontaneously exhibit structural and functional differentiation patterns characteristic of mature enterocytes, with the appearance of brush border microvilli and high activity levels of the enzymes associated with the brush border. Our results concur with other models of folic acid uptake that emphasize the importance of intraluminal factors on micronutrient absorption. Folate uptake declined rapidly between pH 5.8 and 7.5, and was dependent on the initial folate concentration in the media. A dual uptake process is suggested, with a high rate of uptake at folate concentrations below 20 nmol/ml and linear uptake characteristics at higher concentrations.