Retinol binding protein expression is induced in HepG2 cells by zinc deficiency

Zinc (Zn) deficiency is often associated with low plasma vitamin A (retinol ) concentrations. It has been suggested that the reduction in plasma retino l is secondary to reduced liver retinol binding protein (RBP) synthesis. In the present study, REP expression was determined in HepG2 cells cultured i n either Zn adequate media or chelated media containing varying concentrati ons of Zn, Levels of REP mRNA increased in a time- and Zn concentration-dep endent manner such that 0.5 muM Zn-treated cells exhibited a >7.5-fold incr ease while cells treated with 15 muM Zn were increased 2.9-fold at 72 h com pared to controls. REP protein also progressively increased by 72 h to leve ls > 8-fold and 3-fold higher than controls, in 0.5 muM and 15 muM Zn-treat ed cells, respectively. The increase in REP occurred without any change in DNA concentration between groups through 72 h, The Zn deficiency-induced el evations in REP transcript levels could be reversed within 24-48 h of reple tion in Zn adequate media. Thus, the reductions in plasma retinol observed in Zn deficiency are in part a direct consequence of the deficiency. (C) 20 01 Federation of European Biochemical Societies. Published by Elsevier Scie nce B.V. All rights reserved.