Original ArticlesNegative Regulation by Dexamethasone of Fluvastatin-Inducible CYP2B Expression in Primary Cultures of Rat Hepatocytes: Role of CYP3A
Section snippets
Materials
Fluva was a gift from the Sandoz Research Institute. Cycloheximide, Dex, dibutyryl cyclic AMP, glucagon, growth hormone (porcine), PB, triamcinolone, triamcinolone acetonide, and TAO were purchased from the Sigma Chemical Co. Prednisolone and 6β-hydroxyprednisolone were purchased from Steraloids. HPLC solvents were purchased from Burdick & Jackson. Vitrogen (95–98% type I collagen with remainder type III collagen) was purchased from Celtrix. Other supplies and reagents were purchased from the
Results
The primary mechanism through which PB or any other agent induces CYP2B1/2 is not known. However, manipulations that modulate the ability of PB to induce CYP2B in primary hepatocyte culture may provide insight into whether PB and Fluva induce CYP2B through a common mechanism. We therefore examined the effects of several of these manipulations on the levels of CYP2B1/22 RNA induction produced in primary cultured rat hepatocytes treated for 24 hr (beginning 48 hr postplating) with PB or Fluva, at
Discussion
Treatment of primary cultured rat hepatocytes with a variety of agents previously reported to modify PB-inducible CYP2B expression generally produced the expected results. Thus, incubation of cultured rat hepatocytes with fetal bovine serum, growth hormone, or cycloheximide suppressed PB-mediated CYP2B induction, as previously reported 4, 5. Also, maintenance of hepatocytes on a Vitrogen substratum in glucocorticoid-deficient medium did not support PB-inducible CYP2B1/2 mRNA induction, in
Acknowledgements
This work was supported by National Institutes of Health Grant HL50710 and, in part, by NIEHS Center Grant ES06639. The authors thank Dr. Melissa Runge-Morris for her constructive comments during the preparation of this manuscript.
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