Affiliations: Department of Environmental Toxicology, University of
California, Davis, CA 95616, USA
Note: [] Address for correspondence: Dr. Michael S. Denison, Department
of Environmental Toxicology, Meyer Hall, One Shields Ave, University of
California, Davis, CA 95616, USA. Tel.: +1 530 752 3879; Fax: +1 530 752 3394;
E-mail: msdenison@ucdavis.edu
Abstract: In this study, we have compared the time and dose response curves
for TCDD using the pGudLuc1.1-chemically activated luciferase expression
(CALUX) cell bioassay and two new recombinant cell lines that contain a stably
transfected mutated form of firefly luciferase reporter gene (pGudLuc6.1) or
enhanced green fluorescent protein (EGFP) reporter gene (pGreen1.1). The time
course of induction with pGudLuc1.1-containing H1L1.1c2 cells is transient,
with maximal activity observed at 4 hours after treatment with 1 nM TCDD. In
contrast, expression of luciferase from the pGudLuc6.1-containing H1L6.1c2
cells and the pGreen1.1-containing H1G1.1c3 cells progressively increases with
time, with luciferase activity increasing at a significant faster rate than
that of EGFP. Dose response analysis with each cell line at optimal analysis
times reveal similar relative dose response curves and
EC_{50}s for H1L6.1c2 and H1G1.1c3 cells, while the
EC_{50} for TCDD in the H1L1.1c2 cells was about 7-fold
lower. In addition, these bioassay systems respond to halogenated and/or
polycyclic aromatic hydrocarbons in a dose-specific manner. Given the above
differences between cell lines and reporters, the choice of which cell line to
use will certainly be dependent on the specific questions and issues being
examined.
