Ishii Yuji, Akazawa Daisuke, Aoki Yasunobu, Yamada Hideyuki, Oguri Kazuta
Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Biol Pharm Bull. 2005 Jun;28(6):1087-90. doi: 10.1248/bpb.28.1087.
The effect of an aryl hydrocarbon receptor (AhR) ligand on the carbonic anhydrase III (CAIII) mRNA level was studied using primary cultured hepatocytes of rats. CAIII gene which is highly suppressible by dioxins in vivo, was also suppressible in primary cultured hepatocytes of rats by an AhR ligand, 3-methylchlanthrene (3MC). The suppression of CAIII by 3MC was observed in a dose-dependent fashion. The suppression was marked at 10 microM MC. It is likely that AhR is involved in the suppression of the CAIII gene. The transcriptional regulation region of rat CAIII gene was cloned by polymerase chain reaction on the basis of the similarity to the mouse and human CAIII genes. A 1.5 kb section upstream of rat CAIII was sequenced and the transcription initiation site of this gene was mapped to 58 bases upstream of the initiation codon. A xenobiotic responsive element (XRE)-like sequence was found at -555 to -549 bp of the transcription initiation site. The location of XRE-like element was conserved between rats and mice those CAIIIs in liver were shown as dioxins-suppressible. Although the roles of the XRE have not been clarified, these results suggest that the AhR ligands could elicit the suppressive effect on hepatic CAIII and the effect on the factors from extrahepatic tissues is not required for the suppression.
利用大鼠原代培养肝细胞研究了芳烃受体（AhR）配体对碳酸酐酶III（CAIII）mRNA水平的影响。CAIII基因在体内可被二噁英高度抑制，在大鼠原代培养肝细胞中也可被AhR配体3-甲基胆蒽（3MC）抑制。3MC对CAIII的抑制呈剂量依赖性。在10μM 3MC时抑制作用明显。AhR可能参与了CAIII基因的抑制。基于与小鼠和人CAIII基因的相似性，通过聚合酶链反应克隆了大鼠CAIII基因的转录调控区。对大鼠CAIII上游1.5 kb区域进行了测序，并将该基因的转录起始位点定位到起始密码子上游58个碱基处。在转录起始位点的-555至-549 bp处发现了一个类似外源性反应元件（XRE）的序列。在大鼠和小鼠中，肝脏中CAIII可被二噁英抑制，XRE样元件的位置是保守的。虽然XRE的作用尚未阐明，但这些结果表明，AhR配体可对肝脏CAIII产生抑制作用，且这种抑制作用不需要来自肝外组织的因子参与。
