Uptake and distribution of carotenoids, retinol, and tocopherols in human colonic epithelial cells in vivo.

Studies suggest that micronutrients such as the tocopherols, retinol, and the carotenoids have a chemopreventive action against colonic carcinogenesis and that they may be essential for the functioning and structural integrity of the gastrointestinal epithelium. In this study, we have determined the concentrations of tocopherols, retinol, and the carotenoids in human colonic epithelial cells using a noninvasive procedure developed in this laboratory (G.P. Albaugh et al., Int. J. Cancer, 52: 347-350, 1992). In subjects on a normal diet, almost all of these micronutrients were restricted to cells in the density range of rho 1.065-1.090 and rho 1.090-1.110. The lighter fraction (rho 1.033-1.064), representing the most senescent subpopulation, retained these micronutrients only when the subjects were on diets rich in vegetables. Cells isolated from subjects on their usual diets gave the following values expressed as ng/10(7) cells: alpha-tocopherol, 93-151; gamma-tocopherol, 152-280; retinol, 12-20; lutein, 4-18; cryptoxanthin, not detected; lycopene, 0-17; alpha-carotene, 3-7; and beta-carotene, 6-9. Peak responses in specific micronutrients following 5 days on a high carotenoid diet showed a lag period of at least 5 days, corresponding to the turnover rates of the epithelium itself. The evidence suggests that uptake of these micronutrients by the colonic mucosa occurs in the deep cryptal zone where the actively proliferating cells extract the nutrients from the systemic circulation.