Giri S N, Siegel D M
Department of Veterinary Pharmacology and Toxicology, School of Veterinary Medicine, University of California, Davis 95616.
J Biochem Toxicol. 1991 Summer;6(2):137-45. doi: 10.1002/jbt.2570060208.
In this study, we have characterized the covalent binding of [14C]-2-chloro-4-acetotoluidide (CAT) radioactivity to microsomes of starling liver and kidney. The maximal velocity (Vmax) of covalent binding and apparent Michaelis constant (Km) for both tissues were similar. The Vmax for liver and kidney were 52.8 and 68.9 pmol/min/mg protein, and the apparent Kms were 0.54 and 0.87 mM, respectively. The covalent binding of radioactivity to heat-denatured microsomes of liver and kidney was reduced by 62% and 15%, respectively. Incubation at 0 degrees C reduced the binding by 80% to liver and 70% to kidney microsomes. Absence of nicotinamide adenine dinucleotide phosphate (NADP) and molecular O2 reduced the binding to liver microsomes by 36 and 53%, as opposed to 28% increase and 26% decrease in binding to kidney microsomes, respectively. Inducers of cytochrome P450 monooxygenase (P450), phenobarbital, and 3-methylcholanthrene (3-MC), had opposite effects on the covalent binding of [14C]-CAT radioactivity to hepatic and renal microsomes. Phenobarbital increased the binding to hepatic microsomes by 100% and had no effect on binding to renal microsomes. 3-MC, on the other hand, increased the binding to kidney microsomes by threefold and had no effect on the binding to hepatic microsomes. SKF 525A, an inhibitor of P450, inhibited the binding to hepatic microsomes by 60% at 0.5 mM but failed to have any effect on binding to renal microsomes. alpha-Naphthoflavone, another inhibitor of P450, had no effect on the covalent binding of [14C]-CAT radioactivity to microsomes of either tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
在本研究中，我们已对[¹⁴C]-2-氯-4-乙酰甲苯胺（CAT）放射性与欧椋鸟肝脏和肾脏微粒体的共价结合进行了表征。两种组织的共价结合最大速度（Vmax）和表观米氏常数（Km）相似。肝脏和肾脏的Vmax分别为52.8和68.9 pmol/分钟/毫克蛋白质，表观Km分别为0.54和0.87 mM。放射性与肝脏和肾脏热变性微粒体的共价结合分别减少了62%和15%。在0℃孵育使肝脏微粒体的结合减少80%，肾脏微粒体的结合减少70%。缺乏烟酰胺腺嘌呤二核苷酸磷酸（NADP）和分子氧使肝脏微粒体的结合减少36%和53%，而肾脏微粒体的结合分别增加28%和减少26%。细胞色素P450单加氧酶（P450）的诱导剂苯巴比妥和3-甲基胆蒽（3-MC）对[¹⁴C]-CAT放射性与肝脏和肾脏微粒体的共价结合有相反的影响。苯巴比妥使肝脏微粒体的结合增加100%，对肾脏微粒体的结合无影响。另一方面，3-MC使肾脏微粒体的结合增加三倍，对肝脏微粒体的结合无影响。P450抑制剂SKF 525A在0.5 mM时使肝脏微粒体的结合抑制60%，但对肾脏微粒体的结合无任何影响。另一种P450抑制剂α-萘黄酮对[¹⁴C]-CAT放射性与两种组织微粒体的共价结合均无影响。（摘要截于250字）
