Dubey R K, Singh J
Biochemistry Section, Council of Scientific and Industrial Research Jammu Tawi, India.
Biochem Pharmacol. 1988 Jan 15;37(2):169-76. doi: 10.1016/0006-2952(88)90714-9.
To investigate the drug-metabolizing potential of different sub-populations of cells along the villus-crypt surface of the small intestine, the major monooxygenase activities directed towards the substrates benzo[a]pyrene (BP), 7-ethoxycoumarin and ethylmorphine were studied. The cells were isolated in sequential fractions corresponding to the villus tip-to-crypt gradient in the small intestinal epithelium of the rat. Cells from the upper- and mid-villus regions were rich in aryl hydrocarbon (BP)hydroxylase (AHH) and 7-ethoxycoumarin deethylase (7-ECDE) activities whereas in crypt cells the activities of these enzymes were at the level of detectability. Ethylmorphine demethylase (EMD) was not detectable in the entire villus-crypt surface. The intestinal epithelial cells responded strongly to inducers. 3-Methylcholanthrene (3-MC), given to rats 24 hr previously, induced increases in AHH activity of 4- to 7-fold in the villus and of 19- to 26-fold in the crypt cells. 7-ECDE had a similar pattern. The induced level of monooxygenase activity in crypt cells was sustained for a longer time, followed in order by consecutively higher cells of the villus. Phenobarbital caused maximal expression of EMD activity in the mid-villus region whereas the activity in crypt cells was half the maximal activity. PB also significantly induced AHH and 7-ECDE in the intestinal epithelium. 7,8-Benzoflavone inhibited AHH activity to the same degree in all the cell fractions. The apparent Km for AHH was 5 microM (BP). Treatment of rats with 3-MC, after 24 hr, enhanced the Km and Vmax differently in the cells along the villus-crypt surface. The Km value in the villus region increased, whereas it did not change in the crypt cells; Vmax increased 6-fold in the villus and about 12-fold in the crypt cells, above their basal levels. The results suggest that the intestinal cells are capable of biotransforming various xenobiotics. The higher sensitivity of their monooxygenases, particularly of the crypt cells, might protect them directly or render the cells capable of generating metabolites that aid and abet toxicity toward target tissue in vivo.
为了研究沿小肠绒毛 - 隐窝表面不同细胞亚群的药物代谢潜力，我们研究了针对底物苯并[a]芘（BP）、7 - 乙氧基香豆素和乙基吗啡的主要单加氧酶活性。在大鼠小肠上皮中，按照与绒毛顶端到隐窝梯度相对应的顺序分离细胞组分。绒毛上部和中部区域的细胞富含芳烃（BP）羟化酶（AHH）和7 - 乙氧基香豆素脱乙基酶（7 - ECDE）活性，而在隐窝细胞中这些酶的活性处于可检测水平。在整个绒毛 - 隐窝表面均未检测到乙基吗啡脱甲基酶（EMD）。肠上皮细胞对诱导剂反应强烈。提前24小时给大鼠注射3 - 甲基胆蒽（3 - MC），可使绒毛中AHH活性增加4至7倍，隐窝细胞中增加19至26倍。7 - ECDE呈现类似模式。隐窝细胞中单加氧酶活性的诱导水平持续时间更长，随后依次是绒毛中更高位置的细胞。苯巴比妥使绒毛中部区域的EMD活性达到最大表达，而隐窝细胞中的活性为最大活性的一半。PB还显著诱导肠上皮中的AHH和7 - ECDE。7,8 - 苯并黄酮在所有细胞组分中对AHH活性的抑制程度相同。AHH的表观Km值为5μM（BP）。24小时后用3 - MC处理大鼠，沿绒毛 - 隐窝表面的细胞中Km和Vmax的增加情况不同。绒毛区域的Km值增加，而隐窝细胞中未改变；Vmax在绒毛中增加6倍，在隐窝细胞中比基础水平增加约12倍。结果表明肠细胞能够对各种外源性物质进行生物转化。它们的单加氧酶，特别是隐窝细胞的单加氧酶具有更高的敏感性，这可能直接保护它们，或使细胞能够产生有助于并加剧体内对靶组织毒性的代谢产物。
