β‐Carotene uptake, metabolism, and distribution in BALB/c 3T3 cells

Abstract

Although a growing number of epidemiological studies indicate that dietary β‐carotene has anticarcinogenic activity, the mechanism(s) of β‐carotene protection remains to be definitively established. In this context, in vitro studies of β‐carotene have been, and continue to be, valuable. We examined the following critical features in designing an in vitro system for studying the protective action of β‐carotene: 1) form of β‐carotene used for cellular uptake, 2) cellular metabolism of β‐carotene, and 3) subcellular distribution of β‐carotene. It was determined that β‐carotene added to medium in a water‐dispersible formulation is readily taken up by BALB/c 3T3 cells and is located predominantly in cellular membranes. Cellular uptake of β‐carotene added to medium in an organic solvent is greatly reduced. It was also found that intracellular retinol increased significantly after a three‐day exposure of BALB/c 3T3 cells to media containing β‐carotene. This result suggests that the ability to metabolize β‐carotene to retinoids is not limited to cells of intestinal origin. The results and methodology described here will be useful in the rational design of in vitro assays for elucidating the mechanism(s) of β‐carotene protective effects at the cellular level.