3种海洋鱼类肝微粒体EROD活性的测定

根据鱼类的生态习性选择了暖温性近岸底层岩礁鱼类褐菖鲉和浅海底层鱼类黄鳍鲷和黑鲷作为实验动物,系统地研究了0#柴油WSF诱导组和对照组褐菖鲉肝微粒体EROD动力学反应系统的测定条件,确定了最适测定条件为:pH值7.60、温度15℃、底物7-乙氧基异吩恶唑浓度0.5μmol/L、样品蛋白量100—800μg、还原型辅酶II NADPH 70 nmol/mL。诱导组和对照组的最适反应条件没有差别,但是诱导组的酶活性比对照组的高;对照组和诱导组EROD的Km值分别为0.144μmol/L和0.357μmol/L,Vmax值分别为0.466 nmol min-1mg-1蛋白和2.360 nmol min-1mg-1蛋白。首次在我国建立了褐菖鲉肝微粒体EROD活性检测技术。此外,比较了上述3种实验鱼类肝微粒体EROD反应系统的最适pH值和最适温度。结果表明,与褐菖鲉不同,黄鳍鲷和黑鲷肝EROD反应最适pH值都是7.80,最适温度都是25℃。     

氯吡格雷对大鼠肝药物酶CYP3A4 和CYP1A2 表达的影响

目的：氯吡格雷主要由CYP3A4 催化使其激活,CYP1A2 也参与氯吡格雷活化。关于氯吡格雷对肝微粒体酶的影响国内外 文献报道不多,因此本实验通过检测肝细胞色素氧化酶CYP3A4 和CYP1A2 的表达,探讨氯吡格雷对大鼠肝药物酶的影 响。方法：生理盐水为对照组,氯吡格雷设高、中、低三个剂量组（27,13.5,6.75mg/kg/d）,雄性健康大鼠连续灌胃给药7天,脱臼处 死,取肝组织,通过western blot法检测大鼠肝脏CYP3A4 和CYP1A2 蛋白表达情况。结果：1）、氯吡格雷抑制大鼠CYP3A4 蛋白 表达,氯吡格雷高中低剂量组分别比生理盐水组大鼠CYP3A4 蛋白表达量降低（P<0.05）;氯吡格雷低中高剂量组间进行比较,大 鼠CYP3A4 蛋白表达量呈梯度减少（P<0.05）;2）、氯吡格雷抑制大鼠CYP1A2 蛋白表达,氯吡格雷高中低剂量组分别比生理盐水 组大鼠CYP1A2 蛋白表达量降低（P<0.05）,氯吡格雷低中高剂量组间进行比较,大鼠CYP1A2 蛋白表达量呈梯度减少（P<0.05）。 结论：氯吡格雷使肝细胞色素氧化酶CYP3A4 和CYP1A2 的表达量减少,因此氯吡格雷高、中、低3 个剂量组均不同程度的抑制 大鼠肝脏CYP3A4 和CYP1A2 的表达,提示当氯吡格雷与某些主要经CYP3A4 和CYP1A2 代谢的药物合用时,发生代谢性相关 作用的可能性大。     

紫杉醇对食蟹猴和人CYP1A2、CYP3A4及CYP2A6酶代谢的影响

目的探讨紫杉醇对食蟹猴和人肝微粒体CYP1A2、CYP2A6和CYP3A4酶活性的影响。方法采用食蟹猴和人肝脏微粒体,分别以非那西汀、睾丸酮和香豆素分别作为CYP1A2、CYP2A6、CYP3A4的底物,建立CYP1A2、CYP2A6和CYP3A4体外代谢体系。采用不同浓度的紫杉醇分别与上述3种底物共同孵育于肝微粒体代谢体系中。用HPLC法分别测定各底物的代谢产物扑热息痛、6β-羟基睾丸酮、7-羟基香豆素的产生量,计算IC50值,以评估紫杉醇对CYP1A2、CYP2A6和CYP3A4代谢的影响。结果紫杉醇对食蟹猴肝微粒体3种酶的IC50值分别为570±5.9μmol/L、140±2.9μmol/L和无影响;紫杉醇对人肝微粒体3种酶的IC50值分别为193±6.6μmol/L、253±3.6μmol/L和24±1.6μmol/L。结论紫杉醇对食蟹猴肝微粒体CYP1A2和CYP3A4活性具有一定的抑制作用,但对CYP2A6酶的活性几乎没有影响。紫杉醇对人肝微粒体CYP1A2和CYP3A4活性的抑制作用较弱,但对CYP2A6酶的活性抑制作用较强,提示临床上紫杉醇与作为上述酶底物的药物联合用药时应慎重,以避免因中西药物相互作用所导致的不良反应发生。     

鱼肝EROD酶活力诱导作为二噁的水生态毒理学指标

利用离体EROD法对严家湖各氧化塘鱼肝中二噁的毒性效应进行了定量测定,同时与HRGC／HRMS－MID化学分析结果和野外活体暴露鱼肝中EROD活力诱导结果进行了比较。研究发现,各氧化塘中鱼肝的离体、活体EROD测定结果与化学分析结果之间有着极好的相关性。这不仅揭示了鱼肝细胞色素P450系统以EROD酶活力诱导指示可作为二的水生态毒理学指标的可靠性和准确性,同时也表明了活体EROD和离体EROD生物监测方法两者可以相互补充,用于其他环境生物样品中二类毒物的快速筛选。     

氯吡格雷对大鼠肝药物酶CYP3A4和CYP1A2表达的影响

目的：氯吡格雷主要由CYP3A4催化使其激活,CYPlA2也参与氯吡格雷活化。关于氯吡格雷对肝微粒体酶的影响国内外文献报道不多,因此本实验通过检测肝细胞色素氧化酶CYP3A4和CYPlA2的表达,探讨氯吡格雷对大鼠肝药物酶的影响。方法：生理盐水为对照组,氯吡格雷设高、中、低三个剂量组（27,13．5,6．75mg／kg／d）,雄性健康大鼠连续灌胃给药7天,脱臼处死,取肝组织,通过westernblot法检测大鼠肝脏CYP3A4和CYPlA2蛋白表达情况。结果：1）、氯吡格雷抑制大鼠CYP3A4蛋白表达,氯吡格雷高中低剂量组分别比生理盐水组大鼠CYP3A4蛋白表达量降低（P〈0．05）;氯吡格雷低中高剂量组间进行比较,大鼠CYP3A4蛋白表达量呈梯度减少（P〈0．05）;2）、氯吡格雷抑制大鼠CYPlA2蛋白表达,氯吡格雷高中低剂量组分别比生理盐水组大鼠CYPlA2蛋白表达量降低（P〈0．05）,氯吡格雷低中高剂量组间进行比较,大鼠CYPlA2蛋白表达量呈梯度减少（P〈0．05）。结论：氯吡格雷使肝细胞色素氧化酶CYP3A4和CYPlA2的表达量减少,因此氯吡格雷高、中、低3个剂量组均不同程度的抑制大鼠肝脏CYP3A4和CYPlA2的表达,提示当氯吡格雷与某些主要经CYP3A4和CYPlA2代谢的药物合用时,发生代谢性相关作用的可能性大。     

白色念珠菌CYP51蛋白功能性氨基酸残基定点突变、蛋白表达及活性测定

实验设计了白色念珠菌CYP51蛋白功能性氨基酸残基突变体Y118A、Y118F、Y118T、S378A、S378T、H310A、H310R, 并转入基因工程菌D12667中表达。用Western及紫外分光光度法定性、定量检测蛋白, 用GC-MS法测定蛋白代谢活性。结果表明, 成功表达目标蛋白, 蛋白诱导表达量接近微粒体蛋白总量的25%。活性测定表明, 表达的野生型蛋白保持其对天然底物的代谢能力; 相较于野生型蛋白, 突变体蛋白代谢活性不同程度改变, 最多可下降1/2左右。因此, 本研究中成功表达了野生型和     

梯度离心法制备鸡肝微粒体方法的建立

目的：建立梯度离心法制备鸡肝微粒体的方法。方法：利用蔗糖密度梯度离心法制备鸡肝微粒体,经透射电镜和Western—blot检测肝微粒体纯度,BCA法检测总蛋白质含量,CO差示光谱法检测总CYP450含量。结果：电镜下,制备的肝微粒体可清楚见到大量膜囊泡状结构,其它污染细胞器成分较少见;制备的肝微粒体仅与GRtXM抗体特异性结合;肝微粒体总蛋白质含量与总CYP450含量分别为8．749mg／mL和0．763nmol／mg。结论：利用蔗糖梯度密度离心法制备得到高质量鸡肝微粒体蛋白,为鸡细胞色素P450的深入研究奠定了基础。     

UFLC-MS/MS研究胡椒碱在不同种属肝微粒体中的代谢稳定性和代谢表型

应用体外肝微粒体孵育体系,考察胡椒碱在人、SD大鼠、小鼠、恒河猴和比格犬5个种属肝微粒体中的代谢稳定性,比较代谢的种属差异,确定其在人肝微粒体中的代谢表型。通过UFLC-MS/MS检测方法,测定胡椒碱在各个种属肝微粒体中孵育后的剩余浓度,考察他们的代谢稳定性及体外代谢动力学参数。采用化学抑制法考察胡椒碱在人肝微粒体中的代谢表型。结果表明胡椒碱在人、SD大鼠、小鼠、恒河猴和比格犬的肝微粒体中,半衰期T1/2分别为31. 36、48. 46、138. 60、147. 45、165. 00 min;体外固有清除率CLint分别为0. 0442、0. 0286、0. 0100、0. 0094、0. 0084m L/(m L·mg);在人肝微粒体中,胡椒碱主要被CYP3A4和CYP2C9酶代谢。推测胡椒碱在各种肝微粒体中的代谢均相对较稳定,其中大鼠和人的肝微粒体代谢性质最相近,在后续的实验中可以考虑用大鼠的代谢结果预测人的代谢结果;人肝微粒体中参与胡椒碱代谢的酶主要有CYP3A4和CYP2C9。     

苯并[a]芘暴露对三疣梭子蟹鳃、肝胰腺组织毒理学指标的影响

本文研究了三疣梭子蟹(Portunus trituberculatus)在对苯并[a]芘(BaP)富集(15 d)、释放(15d)过程中其鳃和肝胰腺组织的4种毒理学指标的响应.4种毒理学指标分别为7-乙氧基异吩噁唑酮-脱乙基酶(EROD)、谷胱甘肽硫转移酶(GST)、超氧化物歧化酶(SOD)和脂质过氧化(LPO).设置了0.05 μg/L和0.45 μg/L两个实验组以及海水和丙酮对照组.结果显示,在富集阶段,与海水对照组相比,第1天时0.05 μg/L和0.45μg/L实验组鳃、肝胰腺组织的各毒理指标均显著受到诱导(P＜0.05),诱导程度随BaP暴露浓度的增加而增大.而后鳃、肝胰腺组织的EROD、GST活性以及鳃组织的SOD活性达到峰值后下降,肝胰腺组织的SOD活性以及鳃、肝胰腺组织的丙二醛(MDA)含量则持续增加.鳃组织的EROD、GST、SOD活性到达峰值时间早于肝胰腺组织,其活性以及MDA含量也低于肝胰腺组织.在释放阶段,0.45pg/L实验组鳃组织的SOD活性,0.05μ-g/L和0.45 μg/L两个实验组肝胰腺组织的SOD活性均依然显著高于同期海水对照组水平(P＜0.05),其余各浓度实验组鳃、肝胰腺组织均能恢复到同期海水对照组水平(P＞ 0.05).实验结果表明,三疣梭子蟹的鳃组织对于BaP暴露响应时间比肝胰腺组织更早,但均具有一定的恢复能力.     

苯并[a]芘暴露对三疣梭子蟹鳃、肝胰腺组织毒理学指标的影响1

本文研究了三疣梭子蟹(Portunus trituberculatus)在对苯并[a]芘(Ba P)富集(15 d)、释放(15 d)过程中其鳃和肝胰腺组织的4种毒理学指标的响应。4种毒理学指标分别为7-乙氧基异吩噁唑酮-脱乙基酶(EROD)、谷胱甘肽硫转移酶(GST)、超氧化物歧化酶(SOD)和脂质过氧化(LPO)。设置了0.05μg/L和0.45μg/L两个实验组以及海水和丙酮对照组。结果显示,在富集阶段,与海水对照组相比,第1天时0.05μg/L和0.45μg/L实验组鳃、肝胰腺组织的各毒理指标均显著受到诱导(P0.05),诱导程度随Ba P暴露浓度的增加而增大。而后鳃、肝胰腺组织的EROD、GST活性以及鳃组织的SOD活性达到峰值后下降,肝胰腺组织的SOD活性以及鳃、肝胰腺组织的丙二醛(MDA)含量则持续增加。鳃组织的EROD、GST、SOD活性到达峰值时间早于肝胰腺组织,其活性以及MDA含量也低于肝胰腺组织。在释放阶段,0.45μg/L实验组鳃组织的SOD活性,0.05μg/L和0.45μg/L两个实验组肝胰腺组织的SOD活性均依然显著高于同期海水对照组水平(P0.05),其余各浓度实验组鳃、肝胰腺组织均能恢复到同期海水对照组水平(P0.05)。实验结果表明,三疣梭子蟹的鳃组织对于Ba P暴露响应时间比肝胰腺组织更早,但均具有一定的恢复能力。     

Cytochrome P450 1A1 (CYP1A1) in blood lymphocytes evidence for catalytic activity and mRNA expression.

Studies initiated to characterise the catalytic activity and expression of CYP1A1 in rat blood lymphocytes revealed significant activity of 7-ethoxyresorufin-O-deethylase (EROD) in rat blood lymphocytes. Pretreatment with 3-methylcholanthrene (MC) and beta-naphthoflavone (NF) resulted in significant induction in the activity of lymphocyte EROD suggesting that like the liver enzyme, EROD activity in lymphocytes is inducible and is mediated by the MC inducible isoenzymes of P450. The increase in the activity of EROD was associated with a significant increase in the apparent Vmax and affinity of the substrate towards EROD. That this increase in the activity of EROD could be primarily due to the increase in the expression of CYP1A1 isoenzymes was demonstrated by RT-PCR and western immunoblotting studies indicating an increase in the expression of CYP1A1 in blood lymphocytes after MC pretreatment. Significant inhibition in the EROD activity of MC induced lymphocyte by anti-CYP1A1/1A2 and alpha-naphthoflavone further provided evidence that the CYP1A1/1A2 isoenzymes are involved in the activity of EROD in blood lymphocytes. The data indicating similarities in the regulation of CYP1A1 in blood lymphocytes with the liver isoenzyme suggests that factors which may affect expression of CYP1A1 in liver may also affect expression in blood lymphocytes and that blood lymphocytes could be used as a surrogates for studying hepatic expression of the xenobiotic metabolising enzymes.     

Effects of β-naphthoflavone on the cytochrome P450 system,and phase II enzymes in gilthead seabream (Sparus aurata)

The effect of β-naphthoflavone (β-NF) on several catalytic activities of cytochrome P450 (CYP) and phase II enzymes putatively controlled by [Ah]-receptor activation in the liver, heart and kidney of gilthead seabream, was investigated. In the liver, β-NF treatment [intraperitoneal injection (i.p.) 50 mg/kg] resulted in an increase of CYP content, immunoreactive CYP 1A and methoxyresorufin-O-demethylase (MEROD), pentoxyresorufin O-depentylase (PROD) and ethoxyresorufin-O-deethylase (EROD) activities. However, β-NF had no effect on any of the hepatic phase II enzymes examined (benzaldehyde dehydrogenase, propionaldehyde dehydrogenase, glutathione S-transferase, UDP-glucuronyl-transferase, DT-diaphorase). Single i.p. injection of 10 mg/kg β-NF showed a maximal induction of CYP 1A-like protein and EROD activity after 3–7 days. CYP 1A and EROD returned to control levels 18-days post-treatment. β-NF injection also caused a rapid increase of a single band size of mRNA recognized by a CYP 1A1 cDNA fragment from sea bass (Dicentrarchus labrax). Expression of mRNA preceded the increase of EROD activity and declined rapidly by 96 h. Dose–response experiments demonstrated that EROD was significantly enhanced in liver by a single injection of 0.3 mg/kg β-NF and was the most sensitive measurement for CYP 1A-like induction. β-NF treatments also increased the expression of CYP 1A-like protein, mRNA and EROD, but not MEROD and PROD activities in heart and kidney.     

Cytochrome P450 1A isoenzymes in brain cells: Expression and inducibility in cultured rat brain neuronal and glial cells

Studies initiated to determine the expression of CYP1A1/1A2 isoenzymes in the primary cultures of rat brain neuronal and glial cells revealed significant activity of CYP1A-dependent 7-ethoxyresorufin-o-dealkylase (EROD) in microsomes prepared from both rat brain neuronal and glial cells. RT-PCR and immunocytochemical studies demonstrated constitutive mRNA and protein expression of CYP1A1 and 1A2 isoenzymes in cultured neuronal and glial cells. Cultured neurons exhibited relatively higher constitutive mRNA and protein expression of CYP1A1 and 1A2 isoenzymes, associated with higher activity of EROD than the glial cells. Induction studies with 3-methylchlorantherene (MC), a known CYP1A-inducer, resulted in significant concentration dependent increase in the activity of EROD in cultured rat brain cells with glial cells exhibiting a greater magnitude of induction than the neuronal cells. This difference in the increase in enzyme activity was also observed with RT-PCR and immunocytochemical studies, indicating relatively higher increase in CYP1A1 and 1A2 mRNA as well as protein expression in the cultured glial cells when compared to the neuronal cells. The greater magnitude of induction of CYP1A1 in glial cells is of significance, as these cells are components of the blood-brain barrier and it is suggested that they have a potential role in the toxication-detoxication mechanism. Our data indicating differences in the expression and sensitivity of CYP1A1 isoenzymes in cultured rat brain cells will not only help in identifying and distinguishing xenobiotic metabolizing capability of these cells but also in understanding the vulnerability of these specific cell types towards neurotoxicants.     

Structural features of cytochrome P450 1A associated with the absence of EROD activity in liver of the loricariid catfish Pterygoplichthys sp

The Amazon catfish genus Pterygoplichthys (Loricariidae, Siluriformes) is closely related to the loricariid genus Hypostomus, in which at least two species lack detectable ethoxyresorufin-O-deethylase (EROD) activity, typically catalyzed by cytochrome P450 1 (CYP1) enzymes. Pterygoplichthys sp. liver microsomes also lacked EROD, as well as activity with other substituted resorufins, but aryl hydrocarbon receptor agonists induced hepatic CYP1A mRNA and protein suggesting structural/functional differences in Pterygoplichthys CYP1s from those in other vertebrates. Comparing the sequences of CYP1As of Pterygoplichthys sp. and of two phylogenetically related siluriform species that do catalyze EROD (Ancistrus sp., Loricariidae and Corydoras sp., Callichthyidae) showed that these three proteins share amino acids at 17 positions that are not shared by any fish in a set of 24 other species. Pterygoplichthys and Ancistrus (the loricariids) have an additional 22 amino acid substitutions in common that are not shared by Corydoras or by other fish species. Pterygoplichthys has six exclusive amino acid substitutions. Molecular docking and dynamics simulations indicate that Pterygoplichthys CYP1A has a weak affinity for ER, which binds infrequently in a productive orientation, and in a less stable conformation than in CYP1As of species that catalyze EROD. ER also binds with the carbonyl moiety proximal to the heme iron. Pterygoplichthys CYP1A has amino acid substitutions that reduce the frequency of correctly oriented ER in the AS preventing the detection of EROD activity. The results indicate that loricariid CYP1As may have a peculiar substrate selectivity that differs from CYP1As of most vertebrate.     

Modulation of drug-metabolizing enzymes by extracts of a herbal medicine Evodia rutaecarpa in C57BL/6J mice

Evodia rutaecarpa is a traditional Chinese medicine used for the treatment of gastrointestinal disorders and headache. To assess the possible drug interactions, effects of methanol and aqueous extracts of E. rutaecarpa on drug-metabolizing enzymes, cytochrome P450 (CYP), UDP-glucuronosyl transferase (UGT), and glutathione S-transferase (GST) were studied in C57BL/6J mice. Treatment of mice with methanol extract by gastrogavage caused a dose-dependent increase of liver microsomal 7-ethoxyresorufin O-deethylation (EROD) activity. In liver, methanol extract at 2 g/kg caused 47%, 7-, 8-, 4-fold, 81% and 26% increases of benzo(a)pyrene hydroxylation (AHH), EROD, 7-methoxyresorufin O-demethylation (MROD), 7-ethoxycoumarin O-deethylation (ECOD), benzphetamine N-demethylation, and N-nitrosodimethylamine N-demethylation activities, respectively. Aqueous extract at 2 g/kg caused 68%, 2-fold, and 83% increases of EROD, MROD, and ECOD activities, respectively. For conjugation activities, methanol extract elevated UGT and GST activities. Aqueous extract elevated UGT activity without affecting GST activity. Immunoblot analyses showed that methanol extract increased the levels of CYP1A1, CYP1A2, CYP2B-, and GSTYb-immunoreactive proteins. Aqueous extract increased CYP1A2 protein level. In kidney, both extracts had no effects on AHH, ECOD, UGT, and GST activities. Three major bioactive alkaloids rutaecarpine, evodiamine, and dehydroevodiamine were present in both extracts. These alkaloids at 25 mg/kg increased hepatic EROD activity. These results demonstrated that E. rutaecarpa methanol and aqueous extracts could affect drug-metabolizing enzyme activities. Rutaecarpine, evodiamine, and dehydroevodiamine contributed at least in part to the increase of hepatic EROD activity by extracts of E. rutaecarpa. Thus, caution should be paid to the possible drug interactions of E. rutaecarpa and CYP substrates.     

Differential sensitivity of CYP1A to 3,3′,4′,4-tetrachlorobiphenyl and benzo(a)pyrene in two Lepomis species

Although Lepomis species are abundant in a wide variety of habitats throughout North America and could serve as potentially valuable biomonitoring tools, few studies have examined the induction of pollutant biomarkers in this genus. We hypothesized that the induction of cytochrome P-450 1A (CYP1A), a sensitive and widely used indicator of response to aquatic contaminants, would serve as an effective biomarker of organic pollutant exposure in Lepomis species. We examined the response of CYP1A and two of the major pollutant-responsive phase II enzymes, glutathione S-transferase (GST), and uridine diphosphate glucuronyltransferase (UDPGT), in Lepomis exposed to organic pollutants under laboratory and field conditions. Two Lepomis species (longear sunfish, Lepomis megalottis and bluegill, Lepomis macrochirus) were exposed in the laboratory via intraperitoneal injection to corn oil (vehicle), benzo(a)pyrene (BaP) (10 and 50 mg/kg), a polynuclear aromatic hydrocarbon (PAH) or 3,4,3′,4′-tetrachlorobiphenyl (PCB 77) (0.1 and 1.0 mg/kg), a dioxin-like planar halogenated aromatic hydrocarbon (HAH), and sacrificed 2 (BaP) or 7 (corn oil, PCB77) days later. Lepomis hepatic CYP1A exhibited differential sensitivity to these two classes of environmental contaminants. CYP1A activity was weakly induced in bluegill exposed to 1.0 mg/kg PCB 77 (3 fold induction over controls) but strongly induced in both bluegill and longear sunfish exposed to 50 mg/kg BaP (37 and 15 fold induction over controls, respectively). In contrast, hepatic GST activity in both species remained unchanged following the treatment with either compound and hepatic UDPGT activity, which was assessed only in BaP-treated longear sunfish, was unaffected by that chemical, indicating these phase II enzymes may not be sensitive pollutant biomarkers in this genus. Further, longear sunfish collected from a PCB contaminated site displayed relatively low levels of CYP1A activity despite PCB body burdens associated with strong induction of CYP1A activity in other fish species. The strong induction of CYP1A by BaP with much weaker CYP1A response to PCB indicates that CYP1A in Lepomis sp. could be an excellent biomarker for PAH pollution, but may not be a reliable indicator of site contamination by halogenated hydrocarbons. We conclude that Lepomis species provide a useful model for examining the regulation and potential consequences of differential pollutant sensitivity, but that CYP1A in these species should be used with caution as an indicator of halogenated contaminants.     

Noncompetitive mixed-type inhibition of rainbow trout CYP1A catalytic activity by clotrimazole

Over the past two decades a number of antifungal imidazole derivatives have been approved for use in agricultural. The purpose of this study was to characterize the interaction of a model antifungal imidazole compound with a cytochrome P450 isozyme in a species of fish. Clotrimazole inhibited rainbow trout (Oncorhyncus mykiss) hepatic CYP1A-catalyzed ethoxyresorufin O-deethylase (EROD) activity in vivo and in vitro. Although clotrimazole inhibited EROD activity in vivo, it did not effect CYP1A mRNA levels. Addition of clotrimazole to microsomes produced a type II binding spectrum and clotrimazole was determined to be a noncompetitive mixed-type inhibitor of EROD activity with an IC₅₀ of 190 nM. Since antifungal imidazole compounds may be co-applied with other pesticides, inhibition of cytochrome P450 activity by antifungal imidazole compounds may lead to unexpected toxicological interactions.     

Differential regulation of hepatic cytochrome P450 monooxygenases in streptozotocin-induced diabetic rats

The present investigation was carried out to study the expression of major cytochrome P450 (CYP) isozymes in streptozotocin-induced diabetes with concomitant insulin therapy. Male Sprague-Dawley rats were randomly assigned to untreated control, streptozotocin-induced diabetic, insulin-treated groups and monitored for 4 weeks. Uncontrolled hyperglycemia in the early phase of diabetes resulted in differential regulation of cytochrome P450 isozymes. CYP1B1, CYP1A2, heme oxygenase (HO)-2 proteins and CYP1A2-dependent 7-ethoxyresorufin O-deethylase (EROD) activity were upregulated in the hepatic microsomes of diabetic rats. Insulin therapy ameliorated EROD activity and the expression of CYP1A2, CYP1B1 and HO-2 proteins. In addition, CYP2B1 and 2E1 proteins were markedly induced in the diabetic group. Insulin therapy resulted in complete amelioration of CYP2E1 whereas CYP2B1 protein was partially ameliorated. By contrast, CYP2C11 protein was decreased over 99% in the diabetic group and was partially ameliorated by insulin therapy. These results demonstrate widespread alterations in the expression of CYP isozymes in diabetic rats that are ameliorated by insulin therapy.