Relationship between cellular levels of beta‐carotene and sensitivity to genotoxic agents

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Abstract
The usefulness of an in vitro test system to predict the inhibitory effect of beta‐carotene on the genotoxic activity of carcinogens/mutagens was explored. To facilitate the comparison of data obtained from cultured cells (CHO) and from exfoliated human cells, end‐points were used which can be quantitated in both cell systems: the frequency of micronuclei for estimating the effect of genotoxic agents, and cellular levels of beta‐carotene as a protective agent. In CHO cells, beta‐carotene inhibited the clastogenic and micronu‐cleus‐forming effect of methyl methanesulfonate (MMS) and 4‐nitroquinoline‐l‐oxide (4NQO), but had no protective action against gallic acid, tannic acid, an aqueous extract of areca nut or H2O2. The extent of inhibition depended on the ratio of beta‐carotene to MMS. Doses of beta‐carotene which exerted a protective effect in vitro ranged from approximately 2 to 5 ng per 106 CHO cells. Comparable levels of beta‐carotene were previously found to reduce the frequency of micronucleated exfoliated cells from the buccal mu‐cosa of tobacco and areca‐nut chewers (Stich et al., 1984b).