Analysis of gene abnormalities in newly found rats with congenital defect of alcohol metabolism.

Long Evans Cinamon(LEC)和Long Evans Agti(LEA)大鼠是从Long Evans大鼠建立的突变株。LEC大鼠表现为遗传性肝炎和自发性肝细胞癌。我们先前发现，用含5%乙醇的液体饲料喂养的LEA和LEC大鼠均在2周内死于急性乙醇中毒。在本研究中，阐明了这些菌株乙醇代谢的分子异常。乙醇脱氢酶(ADH)和乙醛脱氢酶(ALDH)活性均下降，为对照组的60-75%。对LEC和LEA大鼠肝脏ALDH RNA(ALDH-2外显子3)的核苷酸序列分析表明，在67位密码子上存在CAG到CGG的点突变，这表明在东方人中存在变异的低KM ALDH。除ALDH点突变外，ADH基因还显示出第一类ADH基因第一内含子的异常。TG重复序列长度为98个碱基对，而对照Wistar大鼠为80个碱基对。提示LEC大鼠体内存在TG重复序列的插入，可能是ADH基因转录效率降低的原因之一。相反，Western印迹分析显示，乙醇可诱导LEC大鼠细胞色素P450表达2E1(meos活性)增加8倍，为正常反应。

Long Evans Cinamon (LEC) and Long Evans Agouti (LEA) rats are mutant strains established from Long Evans rats. LEC rats display hereditary hepatitis and spontaneous hepatocellular carcinoma. We preveously found that both LEA and LEC rats fed with liquid diet containing 5% ethanol died within 2 weeks owing to acute ethanol intoxication. In the present study, the molecular abnormalities of ethanol metabolism on these strains were elucidated. Enzymatic activities of both alcohol dehydrogenase (ADH) and acetaldehyde deheydrogenase (ALDH) were decreased at the level of 60-75% of the control Wistar rats. Nucleotide sequence analysis of both LEC and LEA rat liver ALDH RNA (exon 3 of ALDH-2) showed that there was a point mutation ; CAG to CGG at codon 67, indicating the presence of variant low Km ALDH as seen in human oriental people. In addition to ALDH point mutation, ADH gene also showed an abnormality in the first intron of class 1 ADH gene. The sequence length of TG repeat was 98 base pairs, while that of control Wistar rat was 80 base pairs. This result suggests that the insertion of TG repeat was present in LEC rat and may be responsible for the reduction of transcriptional efficiency of ADH gene. In contrast, by Western blot analysis, cytochrome P450 expression 2E1 (MEOS activity) was induced 8 times higher by ethanol feeding in LEC rat, which is normal response.