CYTOTOXIC EFFECT OF BETA-CAROTENE IN-VITRO IS DEPENDENT ON SERUM CONCENTRATION AND SOURCE

In a previous study we reported that beta-carotene solubilized in tetr ahydrofuran (THF) is toxic for human colonic tumor cells in vitro usin g media containing 10% fetal calf serum (FCS). Cytotoxicity was eviden t using beta-carotene concentrations that are achieved in human serum as a result of supplementation with 30 mg beta-carotene/day. In an att empt to determine the mechanism for this toxicity we investigated the effect of beta-carotene when present in human serum as a result of die tary supplementation. This effect was compared to that observed for ce lls incubated in THF-solubilized beta-carotene. The results indicate t hat human serum from subjects with a high concentration of beta-carote ne is not cytotoxic. Subsequent analysis revealed that in contrast to the results using FCS, THF-solubilized beta-carotene is not cytotoxic in the presence of human serum. In addition, the effect observed with FCS is blunted with increasing FCS concentration from greater than or equal to 90% cytotoxicity using 10% FCS to 36% using 100% FCS. The dif ference in results obtained using FCS and human serum may be due to a serum component that is relatively lacking in FCS as compared to human serum.