TY - JOUR
T1 - Regulation of 2‐acetylaminofluorene‐and 3‐methylcholanthrene‐mediated induction of multidrug resistance and cytochrome P450IA gene family expression in primary hepatocyte cultures and rat liver
AU - Gant, Timothy W.
AU - Silverman, Jeffrey A.
AU - Bisgaard, Hanne Cathrine
AU - Burt, Richard K.
AU - Marino, Pamela A.
AU - Thorgeirsson, Snorri S.
PY - 1991
Y1 - 1991
N2 - Previous studies by this laboratory have indicated that expression of the multidrug resistance (mdr) gene can be increased in vivo by exposure to a variety of xenobiotics. Because of the nature of these compounds, it was proposed that mdr gene expression might, at least in part, be regulated by the arylhydrocarbon (Ah) receptor. In the present study, we used a primary hepatocyte culture model to examine the relationship between induction of cytochrome P450IA and mdr expression in vitro. Both 3‐methylcholanthrene (MC) and 2‐acetylamino‐fluorene (AAF) were efficient inducers of mdr expression in this model. Induction of mdr gene expression by both MC and AAF obeyed a log10 concentration/response relationship. In contrast, 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin did not induce mdr expression at concentrations that yielded maximum induction of cytochrome P450IA expression. These data suggest that mdr induction was not mediated via the Ah receptor. Nuclear run‐off analysis indicated that both AAF and MC induced mdr expression by increasing transcription. Primer extension analysis indicated that mdr gene transcription was initiated at one major site 151 bp upstream of the ATG site in both the uninduced and induced state in vivo and in vitro. The sequence of the primer and the site of initiation of gene transcription indicate that the main gene induced was the mdr1b gene.
AB - Previous studies by this laboratory have indicated that expression of the multidrug resistance (mdr) gene can be increased in vivo by exposure to a variety of xenobiotics. Because of the nature of these compounds, it was proposed that mdr gene expression might, at least in part, be regulated by the arylhydrocarbon (Ah) receptor. In the present study, we used a primary hepatocyte culture model to examine the relationship between induction of cytochrome P450IA and mdr expression in vitro. Both 3‐methylcholanthrene (MC) and 2‐acetylamino‐fluorene (AAF) were efficient inducers of mdr expression in this model. Induction of mdr gene expression by both MC and AAF obeyed a log10 concentration/response relationship. In contrast, 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin did not induce mdr expression at concentrations that yielded maximum induction of cytochrome P450IA expression. These data suggest that mdr induction was not mediated via the Ah receptor. Nuclear run‐off analysis indicated that both AAF and MC induced mdr expression by increasing transcription. Primer extension analysis indicated that mdr gene transcription was initiated at one major site 151 bp upstream of the ATG site in both the uninduced and induced state in vivo and in vitro. The sequence of the primer and the site of initiation of gene transcription indicate that the main gene induced was the mdr1b gene.
KW - 2‐acetylaminofluorene
KW - 3‐methylcholanthrene
KW - Multidrug resistance
KW - cytochrome
KW - induction
KW - transcription
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U2 - 10.1002/mc.2940040614
DO - 10.1002/mc.2940040614
M3 - Article
C2 - 1686552
AN - SCOPUS:0026327875
SN - 0899-1987
VL - 4
SP - 499
EP - 509
JO - Molecular Carcinogenesis
JF - Molecular Carcinogenesis
IS - 6
ER -