Effect of natural antioxidants and apocynin on LPS-induced endotoxemia in rabbit

The objective of this study was to compare the prophylactic effects of the natural antioxidant from spinach (NAO) and apocynin, on the hepatic oxidative stress and liver damage induced by lipopolysaccharide (LPS). Male New Zealand rabbits were challenged with LPS with or without 8 days of antioxidant pretreatment. Pretreatment with NAO, but not apocynin, significantly (p < 0.05) decreased the levels of hydroperoxides and malondialdehyde (MDA) in the liver cytosolic fraction and the activity of NADPH oxidase-generated superoxide in the microsomal fraction, compared to LPS alone. The activity of glutathione peroxidase (G-POX) was significantly (p < 0.05) increased in the LPS-treated group, whereas treatment with NAO, but not apocynin, significantly (p < 0.05) decreased G-POX activity. Pretreatment with the same antioxidants had no significant effects on superoxide dismutase (SOD) activity, whereas an increased level of catalase (CAT) was obtained in all LPS-treated groups. TUNEL immunohistochemical staining in the LPS-treated animals indicated that there was no increase in apoptosis outside of necrotic foci. However, apoptotic hepatocytes were observed within areas of focal necrosis in animals exposed to LPS alone or LPS plus apocynin. Hepatocyte cell proliferation was tested by the proliferating-cell nuclear antigen (PCNA) tool, which indicated a proliferative effect in the LPS group, whereas the effect disappeared in the antioxidant-treated groups. The prophylactic effect of NAO on liver pathology and the significant decreases in lipid peroxidation products and NADPH oxidase activity suggest the use of NAO as an efficient strategy for treatment of endotoxemia.     

Levels and subcellular distributions of detoxifying enzymes in the ovarian corpus luteum of the pregnant and non-pregnant pig.

The levels and subcellular distribution of enzymes involved in defenses against reactive oxygen superoxide dismutase (SOD; E.C.1.15.1.1), glutathione peroxidase (GPX; E.C.1.11.1.9), catalase (CAT; E.C.1.11.1.6), and DT-diaphorase (DT; E.C.1.6.99.2) and of the conjugating enzymes glutathione transferase (GST; E.C.2.5.1.18) and p-sulphotransferase (p-ST; E.C.2.8.2.1) in the corpus luteum of ovaries from pregnant and non-pregnant pigs were investigated. In addition, non-protein thiols and glutathione reductase (GRD; E.C.1.6.4.2) were examined in the same manner. The total cytosolic activities of CAT, DT, GRD, and p-ST were significantly increased, whereas total GST activity was decreased in the pregnant corpus luteum compared to the corresponding activities in non-pregnant corpus luteum. In the case of the mitochondrial fraction from pregnant corpus luteum, GPX and GRD displayed significant increases in specific activity. Upon subfractionation of the mitochondrial fraction (i.e. mitoplast preparation), SOD activity was distributed equally between the mitoplasts and the supernatant. CAT and GPX activities were mainly recovered in the supernatant, while the major GRD activity pelleted with the mitoplasts. Microsomes from pregnant corpus luteum demonstrated increased specific GPX activity and decreased SOD activity compared to the non-pregnant corpus luteum. No differences in the non-protein thiol levels in the cytosolic, mitochondrial, or microsomal fractions from the corpus luteum were observed between non-pregnant and pregnant sows.     

Age-related changes in the activities of epoxide hydrolases in different tissues of mice

Age-related changes in epoxide hydrolase (EH) activity in the liver, kidney, lung, and intestine were studied in male C57BL/6 mice of 1 through 30 months of age. Hepatic cytosolic EH activity increased until 15 months after which there was a decline of 59% during senescence (30 months). Hepatic EH activity in the mitochondrial fraction increased until 4 months and decreased thereafter with a 43% decline by 30 months. The hepatic microsomal EH activity increased until 6 months followed by decline of 32% by 30 months. All of these increases and declines were statistically significant. Renal cytosolic EH showed maximum activity at 6 months after which the activity decreased significantly with age. However, renal EH activity in the mitochondrial fraction, in general, did not change substantially with age. Although changes in renal microsomal EH activity were small, the decrease in activity at 9-18 months was significantly lower than at 1 month and 23-30 months. EH activity in the cytosolic, mitochondrial and microsomal fractions of kidney was 2.5-, 2-, and 10-fold less, respectively, than that found in similar subcellular fractions of liver. Cytosolic EH activity in lung and intestine and lung microsomal EH showed variations with age. The intestinal microsomal EH was not detectable under the experimental conditions used.     

Distribution and inducibility of cytosolic epoxide hydrolase in male Sprague-Dawley rats

Cytosolic epoxide hydrolase (cEH) activity has been determined in liver and various extrahepatic tissues of male Sprague-Dawley rats using trans-stilbene oxide (TSO) and trans-ethylstyrene oxide (TESO) as substrates. Large interindividual differences in the specific activity of cytosolic epoxide hydrolase in the liver from more than 80 individual rats were observed varying by a factor of 38. In a randomly selected group of five animals liver cEH varied by a factor of 3.9 and kidney cEH by a factor of 2.7, whereas liver microsomal epoxide hydrolase and lactate dehydrogenase showed only very low variations (1.4- and 1.1-fold, respectively). The individual relative activity of kidney cEH was related to that of the liver. Cytosolic epoxide hydrolase activity was present in all of six extrahepatic rat tissues investigated. Interestingly specific activities were very high in the heart and kidney (higher than in liver), followed by liver greater than brain greater than lung greater than testis greater than spleen. TSO and TESO hydrolases in subcellular fractions of rat liver were present at highest specific activities in the cytosolic and the heavy mitochondrial fraction. As indicated by the marker enzymes, catalase, urate oxidase and cytochrome oxidase, this organelle-bound epoxide hydrolase activity may be of peroxisomal and/or mitochondrial origin. In the microsomal fraction, TSO and TESO hydrolase activity is very low, whereas STO hydrolase activity is highest in this fraction and very low in cytosol. In kidney, subcellular distribution is similar to that observed in liver. None of the commonly used inducers of xenobiotic metabolizing enzymes caused significant changes in the specific activities of rat hepatic cEH (trans-stilbene oxide, alpha-pregnenolone carbonitrile, 3-methylcholanthrene, beta-naphthoflavone, isosafrole, butylated hydroxytoluene, 2,3,7,8-tetrachlorodibenzo-p-dioxin, dibenzo[a,h]anthracene, phenobarbitone). However, clofibrate, a hypolipidemic agent, very strongly induced rat liver cEH (about 5-fold), whereas microsomal epoxide hydrolase activity was not affected. Specific activity of kidney cEH was increased about 2-fold.     

Measurement of contents in organs of selenium- or vitamin E-deficient rat using instrumental neutron activation analysis

The contents of iron (Fe), cobalt (Co), zinc (Zn), and selenium (Se) in the organs (liver, kidney, spleen, heart, lung, and brain) and the liver cell fractions (nuclear, mitochondrial, microsomal, and cytosolic fractions) of Se- or vitamin E (VE)-deficient rats were measured using instrumental neutron activation analysis (INAA). The contents of Fe in the liver of Se-deficient rats, and in the liver and the spleen of VE-deficient rats were increased compared with those in normal rats. Fe contents increased mainly in the microsomal fraction. Contents of Co in the organs and liver cell fractions of Se- and VE-deficient rats were markedly low, reflecting the Co contents in both diets. Contents of Zn in the organs and liver cell fractions of Se- and VE-deficient rats decreased to 60-80% of the contents in normal rats. The Se contents in Se-deficient rat organs except for the kidney, spleen, and brain were below the detectable level under the present conditions. Se contents in VE-deficient rat decreased to 50-80% of those in normal rats in all organs and fractions. It is suggested that oxidative stress due to Se- or VE-deficiency affects the dynamics of Fe and Zn.     

胡黄连苷元（香荚兰乙酮）对失血性休克及内毒素诱导“两次打击”损伤的保护作用

目的:评价胡黄连苷元对大鼠“两次打击”损伤的保护作用.方法:采用大鼠“两次打击”损伤模型(失血性休克40 mmHg 45 min后iv细菌内毒素LPS 150 μg/kg).大鼠随机分为七组:对照组,内毒素组,失血组,失血/内毒素组和失血/内毒素 胡黄连苷元(2.5,5.0,10.0 mg/kg)组.胡黄连苷元溶于复苏液(生理盐水,NS)中并在2 h内经静脉给药。在LPS或NS注射后,观察大鼠8,16,24及48 h存活率;检测肺组织(iv LPS后3 h及6 h)及血清(失血前,失血后及iv LPS/NS后0,0.5,1,2,4,6 h)丙二醛含量;检测肺及肝组织(iv LPS/NS后 3 h及 6 h)髓过氧化物酶活性.结果:与对照组比较,“两次打击”损伤大鼠8 h(64.3％,P<0.05),16 h(35.7％,P<0.01),24 h(28.6％,P<0.01),48 h(14.3％,P<0.01)存活率显著降低;血清及肺组织丙二醛含量显著增多,肺、肝组织髓过氧化物酶活力显著升高.胡黄连苷元剂量依赖性升高失血性休克大鼠平均动脉压(P<0.05),提高大鼠存活率,降低血清及组织丙二醛含量,下调肺及肝组织髓过氧化物酶活力.结论:胡黄连苷元可保护由失血性休克及细菌内毒素诱导的大鼠“两次打击”损伤.     

Comparison of the actions of acebutolol, practolol and propranolol on calcium transport by heart microsomes and mitochondria.

1 The effects of acebutolol, practolol and propranolol (0,5-3 mM) on calcium uptake, calcium binding and ATPase activities of the rabbit and rat heart microsomal and mitochondrial fractions were investigated. 2 Dose-response and time course experiments revealed that propranolol greatly inhibited microsomal and mitochondrial calcium uptake whereas both acebutolol and practolol showed slight depressant effects. 3 The ATPase activities of microsomal and mitochondrial fractions were decreased by acebutolol, practolol and propranolol; however, the latter agent was more effective than the other two. 4 The inhibitory effects of acebutolol, practolol and propranolol on mitochondria and microsomes were not antagonized by adrenaline. 5 Propranolol decreased calcium binding by the microsomal fraction only, whereas acebutolol and practolol had no effect on microsomal or mitochondrial calcium binding. 6 The sensitivity of the rabbit heart subcellular fractions to the beta-adrenoceptor blocking drugs was similar to that of the rat heart; however, the calcium uptake and ATPase activities of microsomes were more sensitive to propranolol than mitochondria in both species. 7 Perfusion of rat hearts with 0.2-1 mM propranolol decreased contractile force, and microsomal and mitochondrial fractions obtained from these hearts accummulated less calcium in comparison to the control. On the other hand, acebutolol and practolol (0.2-1nM) had no appreciable effects on contractile force or subcellular fractions under similar conditions. 8 The negative inotropic effect of propranolol may partly be due to its inhibitory actions on calcium transport by subcellular organelles of the myocardium; the depressant action of propranolol on calcium transport is unlikely to be due to its beta-adrenoceptor blocking property.     

Increased cholesterol epoxide hydrolase activity in clofibrate-fed animals

Cholesterol epoxide hydrolase (mCE) is a microsomal enzyme that hydrolyzes cholesterol-5,6-epoxides (CE) to cholestanetriol (CT). In the present study, hepatic mCE activity was measured in mice pretreated with several different xenobiotics known to induce a variety of hepatic drug-metabolizing enzymes. Only the phenoxyacetate hypolipidemics (clofibrate and ciprofibrate, included in the diet for 14 days) were found to increase hepatic mCE activity (1.8-fold increase). Clofibrate administration also increased rabbit hepatic (2.9-fold increase) and rat and rabbit renal mCE activity (1.5- and 2.3-fold increase respectively). On a subcellular level, mCE activities in rabbit nuclear and light mitochondrial fractions were increased (3.3- and 1.8-fold increase respectively), whereas activities in the cytosolic and heavy mitochondrial fractions were unchanged. In rabbits, clofibrate administration enhanced the hepatic microsomal hydrolysis of CE without increasing the hydrolysis of arene epoxides (benzopyrene-4,5-oxide) or fatty acid epoxides (methyl cis-9,10-epoxystearate). Increase of tissue mCE activity may significantly enhance tissue CT levels. In this light, it is worth noting similarities in the mechanisms of hypocholesterolemic action caused by clofibrate or CT administration.     

Epoxide hydrolase activity in the mitochondrial and submitochondrial fractions of mouse liver

Distribution of epoxide hydrolase activity in subcellular fractions of livers from male Swiss-Webster mice and Sprague-Dawley rats was monitored with trans-β-ethylstyrene oxide, trans-stilbene oxide and benzo[a]pyrene 4,5-oxide following differential centrifugation. With the former two substrates the highest activity was encountered in the cytosolic fraction; however, significant activity was found in the mitochondrial fraction. These fractions hydrated benzo[a]pyrene 4,5-oxide very slowly, and the major benzo[a]pyrene 4,5-oxide hydrolyzing activity was recovered in the microsomal fraction. Using Triton WR-1339-treated mice, it was shown that trans-β-ethylstyrene oxide hydrolyzing activity was predominantly localized in the mitochondria rather than in lysosomes and peroxisomes. Subsequent separation of the mitochondrial fraction into submitochondrial components by swelling, shrinking, and sonication, followed by sucrose density gradient centrifugation, showed that most of the epoxide hydrolyzing activity was present in the matrix and intermembrane space fraction. Significant activity was also present in the outer and inner membrane fractions. However, epoxide hydrolyzing activity in these fractions was reduced if either increased sonication times were used or the fractions were washed, indicating possible contamination of these fractions by the matrix and intermembrane space enzyme(s). The epoxide hydrolase activity in the mitochondrial and cytosolic fractions in mice appeared similar with regard to inhibition, molecular weight, and substrate selectivity.     

CYP isoform induction screening in 96-well plates: use of 7-benzyloxy-4-trifluoromethylcoumarin as a substrate for studies with rat hepatocytes

1. We investigated the nature and roles of various xenobiotic acyl-CoA hydrolases in liver subcellular fractions from rat treated with sulphur-substituted (thia) fatty acids. To contribute to our understanding of factors influencing enzymes involved in the degradation of activated fatty acids, the effects on these activities of the oppositely acting thia fatty acid analogues, the peroxisome proliferating 3-thia fatty acids (tetradecylthioacetic acid and 3- dithiacarboxylic acid), which are blocked for β-oxidation, and a non-peroxisomeproliferating 4-thia fatty acid (tetradecylthiopropionic acid), which undergoes one cycle of β-oxidation, were studied. 2. The hepatic subcellular distributions of palmitoyl-CoA, tetradecylthioacetyl-CoA and tetradecylthiopropionyl-CoA hydrolase activities were similar to each other in the control and 3-thia fatty acid-treated rat. In control animals, most of these hydrolases were located in the microsomal fraction, but after treatment with the 3-thia fatty acids, the specific activities of the mitochondrial, peroxisomal, and cytosolic palmitoyl-CoA, tetradecylthioacetyl-CoA, and tetradecylthiopropionyl-CoA hydrolase activities were significantly increased. This increase in activity was seen mostly for the enzymes using tetradecylthiopropionyl-CoA and tetradecylthioacetyl-CoA as substrates. The increased mitochondrial activities for these two substrates were seen already after 1 day of treatment, whereas the peroxisomal activities increased after 3 days. No stimulation was seen after treatment with the 4-thia fatty acid analogue, tetradecylthiopropionic acid, but a decrease in peroxisomal hydrolase activities for all three substrates was observed. 3. The cellular distributions of clofibroyl-CoA, POCA-CoA, and sebacoyl-CoA hydrolase activities were different from those of the 'long-chain acyl-CoA' hydrolases mentioned above both in the normal and 3-thia fatty acid treated rat. This group of hydrolases was found in the mitochondrial, peroxisomal, and cytosolic fractions. 3-Thia fatty acid treatment increased the activities of clofibroyl-CoA and sebacoyl-CoA hydrolases in all three fractions. Clofibroyl-CoA and sebacoyl-CoA hydrolase activities were increased after 1 day of treatment. Only the cytosolic POCA-CoA hydrolase was stimulated after 3- thia fatty acid treatment after only 1 day of treatment, whereas treatment with the 4-thia fatty acid led to an increase of enzyme activity in the mitochondrial and peroxisomal fractions. 4. Based on the subcellular distributions and specific activities, we suggest that several enzymes exist which may act as regulators of intracellular acyl-CoA levels.     

前列腺素E1脂微球制剂对大鼠急性肺损伤的影响

目的:采用大鼠腹腔注射脂多糖(LPS)复制大鼠急性肺损伤(ALI)模型,评价前列腺素E1脂微球制剂(凯时)对急性肺损伤大鼠的保护作用。方法:雄性健康Sprague Dawley大鼠60只随机分为3组,A组:生理盐水组;B组:LPS模型组;C组:凯时治疗组。动物以硫喷妥纳腹腔注射麻醉,于实验3h分别测量每只大鼠的肺系数,肺通透指数,肺湿重/肺干重,肺组织中髓过氧化物酶(MPO)含量,丙二荃(MDA)和过氧化物歧化酶(SOD)的含量,血清细胞因子TNF-a、IL-12、IL10的浓度,肺组织中NF-KB蛋白的表达,并进行统计学分析。结果:①B组与A组比较,肺系数,肺通透指数,肺湿重/肺干重显著增加(P<0.05);血浆SOD含量,血清细胞因子IL10显著减少(P<0.05);肺组织中髓过氧化物(MPO)活性和丙二荃(MDA)含量,血清细胞因子TNF-a,IL-12显著增加(P<0.05)。②C组与B组比较,肺系数,肺通透指数,肺湿重/肺干重显著减少(P<0.05);肺组织SOD含量,血清细胞因子IL10显著升高(P<0.05);肺组织中髓过氧化物(MPO)活性和丙二荃(MDA)含量,血清细胞因子TNF-a,IL-12显著减少(P<0.05)。③C组与B组比较,NF-kB P65的表达明显低于A组(P<0.05)。结论:前列腺素E1脂微球制剂通过抑制NF-kB的表达,减少中性粒细胞的渗出,对LPS诱导的急性肺损伤大鼠有明显保护作用。     

丹酚酸A激活AKT/mTOR/4EBP1通路缓解脂多糖诱导的H9c2心肌细胞凋亡和氧化应激

目的探究丹酚酸A(Sal A)对脂多糖(LPS)诱导的氧化应激性损伤H9c2心肌细胞增殖、凋亡,以及蛋白激酶B(AKT)/哺乳动物雷帕霉素靶蛋白(mTOR)/起始因子4E结合蛋白(4EBP1)通路相关蛋白表达的影响。方法用LPS诱导制备H9c2心肌细胞氧化应激性损伤模型,分别用含Sal A 5,10和20 mg·L^-1的DMEM培养基培养细胞24 h,加LPS 1 mg·L^-1继续孵育24 h。用5-乙炔基-2’脱氧尿嘧啶核苷(EdU)染色观察H9c2心肌细胞存活;采用流式细胞术检测H9c2心肌细胞凋亡和线粒体膜电位;用试剂盒检测细胞培养液中乳酸脱氢酶(LDH)和超氧化物歧化酶(SOD)活性及丙二醛(MDA)和谷胱甘肽(GSH)含量;Western印迹法检测胱天蛋白酶3、胱天蛋白酶9、存活蛋白、Bax/Bcl-2,AKT、磷酸化AKT(p-AKT)、mTOR、p-mTOR、4EBP1和p-4EBP1蛋白表达水平。结果与细胞对照组比较,模型组EdU红色标记的细胞减少(P<0.05);与模型组比较,Sal A 5,10和20 mg·L^-1处理组EdU红色标记的细胞增多(P<0.05)。Sal A能降低培养液中LDH活性及细胞内MDA和GSH含量,增加胞内SOD活性(P<0.05),减少心肌细胞的凋亡率(P<0.05),降低心肌细胞线粒体膜电位的下降速度(P<0.05)。Sal A 10和20 mg·L^-1处理后,活化胱天蛋白酶3、活化胱天蛋白酶9和Bax/Bcl-2蛋白水平显著下调(P<0.05),存活蛋白水平显著上调(P<0.05);与细胞对照组比较,模型组AKT/mTOR/4EBP1磷酸化水平均显著降低(P<0.05)。与模型组比较,Sal A 10和20 mg·L^-1组AKT和mTOR磷酸化水平均显著升高(P<0.05)。结论Sal A通过激活AKT/mTOR/4EBP1通路、减少心肌细胞凋亡并降低心肌细胞线粒体膜电位的下降速度,减缓了LPS诱导的H9c2心肌细胞凋亡和氧化应激,表明Sal A对LPS造成的氧化应激损伤心肌细胞具有保护作用。     

Reduction of the potential anticancer drug oracin in the rat liver in-vitro

Studies on the metabolism of the potential cytostatic drug oracin have shown that a principal metabolite of oracin is 11-dihydrooracin (DHO). We conducted in-vitro experiments to investigate the extent of oracin carbonyl reduction in microsomal or cytosolic fractions and to find out the enzymes involved under these conditions. Among several inducers of rat cytochrome P450 only 3-methylcholanthrene caused a significant (P < 0.01) stimulation (1.9 times) of DHO production in microsomal fraction and the specific P4501A inhibitor alpha-naphthoflavone significantly (P < 0.01) decreased (twice) the induced reduction activity. Cytochrome P4501A participates in oracin reduction in microsomes. 18beta-Glycyrrhetinic acid, a specific inhibitor of hydroxysteroid dehydrogenase, significantly (P < 0.01) inhibited the production of DHO in the microsomal fraction (>95% inhibition) in comparison with the non-inhibited reaction. Statistically significant (P < 0.01) inhibition (95%) of DHO formation was caused by metyrapone, which is also the substrate of 11-hydroxysteroid dehydrogenase. The main microsomal enzyme which catalyses the carbonyl reduction of oracin is probably 11beta-hydroxysteroid dehydrogenase. Important oracin reduction to DHO in the cytosolic fraction was found. According to its specific sensitivity towards quercitrin (inhibition by 99%, P < 0.01), the enzyme responsible for DHO formation in the rat liver cytosol is postulated to be carbonyl reductase.     

Effects of apocynin and natural antioxidant from spinach on inducible nitric oxide synthase and cyclooxygenase-2 induction in lipopolysaccharide-induced hepatic injury in rat

The immunoreactivity of inducible nitric oxide synthase, and cyclooxygenase-2 was compared among groups of male Wistar rats comprising those injected with lipopolysaccharide following pretreatment with either natural antioxidant from spinach or the antioxidant apocynin, with lipopolysaccharide without pretreatment with antioxidants, with each of the two antioxidants alone, and untreated controls. The grade of staining of both inducible nitric oxide synthase and cyclooxygenase-2 increased with the severity of the inflammatory reaction in the lipopolysaccharide-treated animals, compared to the antioxidant-treated groups. Interpretation of the results of the immunostained tissues indicated that pretreatment with either antioxidant significantly (P<0.05) attenuated the lipopolysaccharide-stimulated inducible nitric oxide synthase induction. Analysis of the cycloxygenase-2-stained liver samples indicated that the pretreatment with the natural antioxidant NAO significantly (P<0.05) attenuated lipopolysaccharide-stimulated cycloxygenase-2 induction; whereas, in animals pretreated with apocynin, there was a trend of reduction in the cyclooxygenase-2 expression, but not statistically significant (P>0.05). The negative nitrotyrosine immunoreactivity of the lipopolysaccharide-related hepatic lesions may indicate that there was relatively low interaction between superoxide anions and nitric oxide to form peroxynitrite or that the expression levels of the nitrotyrosine were below the limit of detection. In all treatment groups a positive correlation (P<0.05, r=0.86) found between the inducible nitric oxide synthase and cyclooxygenase-2 scores suggests a strong relationship between these two parameters. The results indicate the possible therapeutic efficacy of NAO and apocynin in the prevention of liver damage related to clinical endotoxemia known to be associated with oxidative stress.     

Effect of in vivo administered hexachlorobenzene on epidermal growth factor receptor levels,protein tyrosine kinase activity,and phosphotyrosine content in rat liver

In the present study, the effects of hexachlorobenzene (HCB) on epidermal growth factor receptor (EGFR) content of liver microsomes and plasma membrane, and on EGFR-tyrosine kinase activity in the microsomal fraction were investigated. In addition, we studied the parameters of the tyrosine kinase signalling pathway such as protein tyrosine kinase (PTK) activity and phosphotyrosine content in microsomal and cytosolic protein. To determine whether the observed alterations were correlated with a manifestation of overt toxicity, a single very low dose of HCB (1mg/kg body wt) and two much higher doses (100 and 1000 mg/kg body wt), the highest being toxicologically significant in that it reduced serum thyroxine (T(4)) and inhibited uroporphyrinogen decarboxylase (URO-D) (EC 4.1.1.37) activity, were tested. Our results demonstrated that liver microsomes of rats treated with HCB had higher levels of EGFR than untreated rats; treated rats also had less EGFR present in hepatocyte plasma membrane fractions than did untreated rats. HCB altered the phosphotyrosine content and protein phosphorylation of some microsomal and cytosolic proteins in a biphasic dose-response relationship. At the low dose, phosphorylation and phosphotyrosine content of several microsomal proteins were increased; however, these effects were diminished or reversed at the higher doses. Our results suggest that chronic HCB treatment produces a down-regulation of the EGFR and a dose-dependent increase in EGFR-tyrosine kinase activity in the microsomal fraction. This effect may contribute to the alteration of membrane and cytosolic protein tyrosine phosphorylation. The level of sensitivity encountered in our studies is extraordinary, occurring at 1/10 to 1/1000 the doses of HCB known to cause other toxicological lesions.     

Effect of 3- and 4-thia-substituted fatty acids on glycerolipid metabolism and mitochondrial beta-oxidation in rat liver

Treatment of normolipidemic rats by alkylthiopropionic acid (CETTD), resulted in a dose- and time-dependent increase in total dihydroxyacetone phosphate acyltransferase (DHAPAT) activity, in extent comparable to that of 3-thiadicarboxylic acid (BCMTD) and alkylthioacetic acid (CMTTD). Thus, in CETTD- and CMTTD-treated rats, the specific DHAPAT activity increased in the microsomal, peroxisomal and mitochondrial fractions. In contrast, repeated administration of the peroxisome proliferator, BCMTD, decreased the specific DHAPAT activity both in the peroxisomal fraction and in purified peroxisomes. A three-fold increase in specific activity was, however, revealed in the mitochondrial fraction. Whether the variation of the DHAPAT activity in the mitochondrial and microsomal fractions among the feeding groups can be explained by increased number of enlarged and small peroxisomes sedimenting in the fractions, are to be considered. Subcellular fractionation studies confirmed previous findings that rat liver glycerophosphate acyltransferase (GPAT) was located both in mitochondria and the microsomal fraction. BCMTD was considerably more potent than CMTTD in stimulating the microsomal and mitochondrial GPAT activities. Administration of CETTD marginally affected the isoenzymes of GPAT. Diacylglycerol acyltransferase (DGAT) activity was increased by 35% in BCMTD and CMTTD treated rats, but by administration of CETTD the enzyme activity was decreased by more than 80%. The acyl-CoA cholesterol acyltransferase (ACAT) activity was marginally affected in animals treated with BCMTD, CMTTD and CETTD. Thus, the results indicate that the initial steps in the synthesis of triacylglycerols and ether glycerolipids as well as the last step in triacylglycerol synthesis could not be identified as mediating the fat accumulation or the lowering of triacylglycerol content in liver of CETTD, or BCMTD and CMTTD treated rats. On the other hand, CMTTD increased the palmitoyl-CoA oxidation in mitochondria, and CETTD considerably inhibited the activity. Therefore, it is conceivable that the development of fatty liver with CETTD is mostly due to inhibition of mitochondrial beta-oxidation.     

Biochemical and ultrastructural alterations in the rat ventral prostate due to repetitive alcohol drinking

Previous studies showed that cytosolic and microsomal fractions from rat ventral prostate are able to biotransform ethanol to acetaldehyde and 1-hydroxyethyl radicals via xanthine oxidase and a non P450 dependent pathway respectively. Sprague Dawley male rats were fed with a Lieber and De Carli diet containing ethanol for 28 days and compared against adequately pair-fed controls. Prostate microsomal fractions were found to exhibit CYP2E1-mediated hydroxylase activity significantly lower than in the liver and it was induced by repetitive ethanol drinking. Ethanol drinking led to an increased susceptibility of prostatic lipids to oxidation, as detected by t-butylhydroperoxide-promoted chemiluminiscence emission and increased levels of lipid hydroperoxides (xylenol orange method). Ultrastructural alterations in the epithelial cells were observed. They consisted of marked condensation of chromatin around the perinuclear membrane, moderate dilatation of the endoplasmic reticulum and an increased number of epithelial cells undergoing apoptosis. The prostatic alcohol dehydrogenase activity of the stock rats was 4.84 times lower than that in the liver and aldehyde dehydrogenase activity in their microsomal, cytosolic and mitochondrial fractions was either not detectable or significantly less intense than in the liver. A single dose of ethanol led to significant acetaldehyde accumulation in the prostate. The results suggest that acetaldehyde accumulation in prostate tissue might result from both acetaldehyde produced in situ but also because of its low aldehyde dehydrogenase activity and its poor ability to metabolize acetaldehyde arriving via the blood. Acetaldehyde, 1-hydroxyethyl radical and the oxidative stress produced may lead to epithelial cell injury.     

Profile of drug metabolizing enzymes in the nuclear and microsomal fractions from rat liver nodules and normal liver

The activities of UDP-glucuronyl transferase, DT-diaphorase, epoxide hydrolase, aryl hydrocarbon hydroxylase, -glutamyl transferase and NADPH-cytochrome c reductase were measured in the nuclear and microsomal fractions from normal rat liver and rat liver nodules. Nodules were produced by intermittent feeding of Wistar rats with a standard diet supplemented with 0.05% (w/w) 2-acetylaminofluorene. The nuclear and microsomal fractions were isolated by differential centrifugation. The activities of UDP-glucuronyl transferase, DT-diaphorase, epoxide hydrolase and -glutamyl transferase were significantly increased in the nuclear and microsomal fractions obtained from nodules as compared with normal liver. Aryl hydrocarbon hydroxylase activity was decreased in the microsomal fraction from the pathological tissue but not in the nuclear fraction. NADPH-cytochrome c reductase activity was similar in nodular and normal liver tissue. The nuclear/microsomal ratio for phase I reactions in xenobiotic metabolism was increased over normal more than two fold. Thus the nuclear and microsomal systems for drug metabolism are both changed in liver nodules. The relative enhancement of nuclear activating reactions is remarkable in the light of the increased risk for malignant transformation exhibited by nodular cells.     

Subcellular distribution and properties of rabbit liver aldehyde dehydrogenases

In rabbit liver, both NAD⁺- and NADP⁺-dependent aldehyde dehydrogenases were identified. The activities were distributed among at least three major groups of isozymes identifiable by gel electrophoresis. These isozymes also differed in their substrate and coenzyme preferences, subcellular distributions, and/or responses to effectors. The NAD⁺-dependent aldehyde dehydrogenase activity was distributed among the mitochondrial, microsomal, and cytosolic fractions. The NADP⁺-dependent aldehyde dehydrogenase activity was largely microsomal, with little true cytosolic NADP⁺-dependent activity demonstrable. Aliphatic aldehydes were oxidized equally well by aldehyde dehydrogenases in all three fractions. Aromatic aldehydes, however, were preferentially oxidized by microsomal aldehyde dehydrogenases. Disulfiram significantly inhibited mitochondrial (45 per cent) and cytosolic (93 per cent) NAD⁺-dependent aldehyde dehydrogenase, but it did not cause significant inhibition of microsomal NAD⁺-dependent activity. Disulfiram inhibited the NADP⁺-dependent aldehyde dehydrogenase activity (>71 per cent) in all subcellular fractions. Diethylstilbestrol activated both NAD⁺- and NADP⁺-dependent aldehyde dehydrogenases in mitochondria and cytosol. Microsomal aldehyde dehydrogenases were not affected by diethylstilbestrol.     

The in vitro ketone reduction of warfarin and analogues. Substrate stereoselectivity, product stereoselectivity and species differences

The in vitro metabolic ketone reduction of warfarin and its 4'-analogues acenocoumarol (4'-nitrowarfarin) and 4'-chlorowarfarin has been investigated using microsomal and cytosolic fractions of several species. Both subcellular fractions showed ketone reductase activity. The cytosolic fractions, in most species, exhibited strong substrate stereoselectivity as well as product stereoselectivity, i.e. the R(+)enantiomer was preferred as a substrate to be reduced mainly to the RS alcohol. Phenobarbital and methylcholanthrene induced cytosolic ketone reductase activity in the rat 5- to 11-fold and 3- to 7.4-fold, respectively. The microsomal fractions also showed substrate and product stereoselectivity. Contrary to the cytosolic fractions a general pattern for substrate and product stereoselectivity could not be seen. Stereoselectivity seemed species dependent (e.g. sheep vs bovine and pig). Rat liver microsomes showed practically no ketone reductase activity. Induction by phenobarbital or methylcholanthrene resulted in only a slight rise, if any, in rat microsomal ketone reductase activity. Both cytosolic and microsomal ketone reductases proved to be NADPH dependent. Substitution of the 4'-hydrogen of warfarin resulted in a change in reduction rates and in some cases, even in a change in substrate or product stereoselectivity. The data indicate that microsomal ketone reductases are different from cytosolic ketone reductases. Prelog's rule for product stereoselectivity of metabolic ketone reduction, when applied to the ketone reduction of the warfarin analogues did not agree with all data presented here.