Decreased expression of γ-glutamyltranspeptidase in the intestinal cell line caco-2 by inducers of cytochrome p450 1a1

Our purpose was to investigate whether inducers of cytochrome P450 1A1 ( CYP1A1), which cause a decreased expression in Caco-2 cells, at both the mRNA and protein levels, of membrane proteins associated with the uptake and transport of hexoses, would also affect the expression of γ-glutamyltranspeptidase (γGT) (EC 2.3.2.2). In Caco-2 clonal TC7 cells grown under standard conditions (25 mM glucose), exposure to β-naphthoflavone (β-NF), 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin, and 3-methylcholanthrene resulted in increased glucose consumption and decreased γGT activity in cells grown to confluence, i.e. when the differentiation is optimum. γGT activity was further analyzed during the time course of differentiation of TC7 cells treated or not with β-naphthoflavone: while γGT activity in untreated cells showed a 10-fold increase from the exponential phase of growth until late postconfluence, γGT activity in β-NF-treated cells, although increasing by 4-fold, remained at a much lower level (