CAAT-binding transcription factor(CTF) proteins are implicated in the expression of multipleforms and are probably identical to nuclear facfor-1(NF-1). In herpes simplex virus thymidinekinase gene, CTF is required not only to induce basal transcription of this gene, but also tostimlulate the transcription of this gene by thyroid hormone. Gel mobility shift assays and biotin-avidin protein-DNA binding assays were performed to investigate if the synthesis of transcription factors which bind to CCAAT sequences of the TK promoter(CTF or CTF-like factors) is stimulated by T₃ and to kdentify the CCAAT-binding proteins in GH₄C₁ cells havingendogenous thyroid hormone receptors. There are two different sized(31 and 33 kDa) CCAAT-binding proteins in GH₄C₁ cells having endogenous thyroid hormone receptors. The synthesisof these CTF-binding proteins were not affected by T₃.

Cytochrome P-450(CYP) enzymes are important in catalyzing the hiotransffrmation on manyendogeneous compounds and xenobiotics, including drugs and carcinogens. In the presentstudy, effect of nifedipine a voltage dependent calcium channel blocker on the induction ofCYP1A1 and 2B1 was investigated. Change of CYP1A1 and 2B1 activities were measuredby using specific enzyme activities and Western blot analysis. CYP1A1, as quantified by ethoxyresorufin-0-deethylase activity and Western blot with monoclonal antibody 1-7-1, increasedin liver microsome of nifedipine-treated spontaneous hypertensive rat(SHR. 30mg/kg.b.w, twicea day for 3days) but not in kidney microsome. CYP2B1, as quantified by benzyloxyresorufin-O-dealkylase activity and Western blot wit]1 monoclonal antibody 2-66-3, markedly increasedin liver microsome of nifedipine-treated SHR but slightly in kidney microsome. The resultsdemonstrate that nifedipine is a potent inducer of CYP2B1 in SHR.

No abstract available in English.