![]() |
|
|
Vol. 30, Issue 3, 240-246, March 2002
Department of Pharmacology, Toxicology, and Therapeutics,
University of Kansas Medical Center, Kansas City, Kansas
Treatment of rats with the microsomal enzyme inducers
pregnenolone-16
-carbonitrile (PCN), 3-methylcholanthrene (3-MC), and Aroclor 1254 [PCB (polychlorinated biphenyl)] has been shown to decrease circulating levels of thyroid hormones as well as increase microsomal glucuronidation of thyroxine (T4). In addition,
PCN increases triiodothyronine (T3) uridine diphosphate
glucuronosyltransferase (UGT) activity. Members of the UGT1A
family are believed to glucuronidate T4, specifically
UGT1A1 and UGT1A6, whereas the UGT2 family is believed to glucuronidate
T3, namely UGT2B2. The purpose of this study was to
determine whether the aforementioned microsomal enzyme inducers
increase the mRNAs that encode these and other UGT enzymes in rat
liver. Male Sprague-Dawley rats were fed a control diet or a diet
containing PCN (1000 ppm), 3-MC (250 ppm), or PCB (100 ppm) for 7 days,
at which time livers were collected. Increases in mRNA were detected by
QuantiGene branched DNA signal amplification. A 3-fold increase
in UGT1A1 mRNA was produced by PCN in addition to increases in UGT1A2
(4-fold) and UGT1A5 (2-fold) mRNA. PCN affected neither UGT2B2 nor any
other UGT2B mRNA level. 3-MC and PCB increased UGT1A6 mRNA 6- and
4-fold, respectively. 3-MC and PCB each increased UGT1A7 mRNA 4-fold
but did not significantly increase any other UGT mRNAs. These findings
suggest that PCN enhances T4 UGT activity by increased
expression of UGT1A1 and that 3-MC and PCB enhance T4 UGT
activity by increased expression of UGT1A6. These findings also suggest
that increased T3 UGT activity produced by PCN is due to a
mechanism other than increased transcription of UGT2B2, possibly
increased UGT2B2 protein or induction of another UGT enzyme.
This article has been cited by other articles:
![]() |
L. Lecureux, M. Z. Dieter, D. M. Nelson, L. Watson, H. Wong, B. Gemzik, C. D. Klaassen, and L. D. Lehman-McKeeman Hepatobiliary Disposition of Thyroid Hormone in Mrp2-Deficient TR- Rats: Reduced Biliary Excretion of Thyroxine Glucuronide Does Not Prevent Xenobiotic-Induced Hypothyroidism Toxicol. Sci., April 1, 2009; 108(2): 482 - 491. [Abstract] [Full Text] [PDF] |
||||
![]() |
Z. Tong, H. Li, I. Goljer, O. McConnell, and A. Chandrasekaran In Vitro Glucuronidation of Thyroxine and Triiodothyronine by Liver Microsomes and Recombinant Human UDP-Glucuronosyltransferases Drug Metab. Dispos., December 1, 2007; 35(12): 2203 - 2210. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Emi, S.-i. Ikushiro, and Y. Kato Thyroxine-Metabolizing Rat Uridine Diphosphate-Glucuronosyltransferase 1A7 Is Regulated by Thyroid Hormone Receptor Endocrinology, December 1, 2007; 148(12): 6124 - 6133. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. C. Wolf, J. W. Allen, M. H. George, S. D. Hester, G. Sun, T. Moore, S.-F. Thai, D. Delker, E. Winkfield, S. Leavitt, et al. Toxicity Profiles in Rats Treated with Tumorigenic and Nontumorigenic Triazole Conazole Fungicides: Propiconazole, Triadimefon, and Myclobutanil Toxicol Pathol, December 1, 2006; 34(7): 895 - 902. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Luci, H. Kluge, F. Hirche, and K. Eder Clofibrate Increases Hepatic Triiodothyronine (T3)- and Thyroxine (T4)-Glucuronosyltransferase Activities and Lowers Plasma T3 and T4 Concentrations in Pigs Drug Metab. Dispos., November 1, 2006; 34(11): 1887 - 1892. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. K. Shelby and C. D. Klaassen Induction of Rat UDP-Glucuronosyltransferases in Liver and Duodenum by Microsomal Enzyme Inducers That Activate Various Transcriptional Pathways Drug Metab. Dispos., October 1, 2006; 34(10): 1772 - 1778. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. Nishimura, J. Yonemoto, H. Nishimura, S.-i. Ikushiro, and C. Tohyama Disruption of Thyroid Hormone Homeostasis at Weaning of Holtzman Rats by Lactational but Not In Utero Exposure to 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Toxicol. Sci., May 1, 2005; 85(1): 607 - 614. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Wong, L. D. Lehman-McKeeman, M. F. Grubb, S. J. Grossman, V. M. Bhaskaran, E. G. Solon, H. S. L. Shen, R. J. Gerson, B. D. Car, B. Zhao, et al. Increased Hepatobiliary Clearance of Unconjugated Thyroxine Determines DMP 904-Induced Alterations in Thyroid Hormone Homeostasis in Rats Toxicol. Sci., April 1, 2005; 84(2): 232 - 242. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M. Maglich, J. Watson, P. J. McMillen, B. Goodwin, T. M. Willson, and J. T. Moore The Nuclear Receptor CAR Is a Regulator of Thyroid Hormone Metabolism during Caloric Restriction J. Biol. Chem., May 7, 2004; 279(19): 19832 - 19838. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Desaulniers, K. Leingartner, B. Musicki, A. Yagminas, G.-H. Xiao, J. Cole, L. Marro, M. Charbonneau, and B. K. Tsang Effects of Postnatal Exposure to Mixtures of Non-ortho-PCBs, PCDDs, and PCDFs in Prepubertal Female Rats Toxicol. Sci., October 1, 2003; 75(2): 468 - 480. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. R. Dalton, R. T. Miller, and S. A. Meyer The Herbicide Metolachlor Induces Liver Cytochrome P450s 2B1/2 and 3A1/2, but Not Thyroxine-Uridine Dinucleotide Phosphate Glucuronosyltransferase and Associated Thyroid Gland Activity International Journal of Toxicology, July 1, 2003; 22(4): 287 - 295. [Abstract] [PDF] |
||||
![]() |
N. Nishimura, J. Yonemoto, Y. Miyabara, M. Sato, and C. Tohyama Rat Thyroid Hyperplasia Induced by Gestational and Lactational Exposure to 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Endocrinology, May 1, 2003; 144(5): 2075 - 2083. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. K. Shelby, N. J. Cherrington, N. R. Vansell, and C. D. Klaassen Tissue mRNA Expression of the Rat UDP-Glucuronosyltransferase Gene Family Drug Metab. Dispos., March 1, 2003; 31(3): 326 - 333. [Abstract] [Full Text] [PDF] |
||||