A Novel Gene Required for the Alkaliphily of the Facultative Alkaliphile Bacillus sp. Strain C-125

This study clarifies the effect of exposure to cigarette smoke on L-ascorbic acid (AsA) metabolism and on the activities of drug-metabolizing enzymes. Male Wistar rats were used. The test rats (group T) were exposed to sidestream smoke from cigarette for 2 h every day for 25 days. During the experimental period, the excreted amount of AsA in the urine from group T was higher than that from the control group (group C). At the end of the experimental period, the AsA content of the plasma and tissues, the liver cytochrome P-450 content and the activities of drug-metabolizing enzymes in group T were each higher than those in group C.     

Effects of non-ortho-substituted polychlorinated biphenyls (congeners 77 and 126) on cytochrome p4501a and conjugation activities in rainbow trout (Oncorhynchus mykiss)

Immature rainbow trout (Oncorhynchus mykiss) in two separate experiments received a single intraperitoneal injection of 0.1, 1 and 5 mg/kg of either 3,3′,4,4′-tetra- or 3,3′,4,4′,5-pentachlorobiphenyl (IUPAC congeners 77 and 126, respectively). The experiments were run at water temperatures of 6 °C and 4 °C. Fish were killed 6 days after the injection. Biotransformation enzyme activities and cytochrome P4501A (CYP1A) amount and occurrence in different tissues were assayed. Congeners 77 and 126 strongly induced 7-ethoxyresorufin O-deethylase (EROD) and benzo(α)pyrene hydroxylase (AHH) activities in liver and kidney of rainbow trout. The induction of these cytochrome P4501A dependent monooxygenases was dose-related especially with congener 77 in the kidney. However, in the liver the highest dose of both congeners and in kidney the highest dose of congener 126 did not increase the catalytic monooxygenase activities as much as would have been expected based on the responses obtained with the lower doses. This may be because the monooxygenase activities already had attained their maximal induction capacity at 1 mg/kg dose of each congener. The PCB residues in liver were also determined and found to be highest after 5 mg/kg injections (610 μg/kg wet weight with congener 77 and 220 μg/kg with congener 126). When cytochrome P4501A protein content was measured, the induction of cytochrome P4501A was still on the increase even in those cases where catalytic activity failed to show any further induction. Immunohistochemical samples from liver, kidney and intestine showed cytochrome P4501A staining which strongly correlated with cytochrome P4501A in microsomes. Such observations suggest that the amount and occurrence of P4501A in the tissues can express the induction even when catalytic activities seem to be suppressed. With respect to enzymes mediating conjugation reactions, hepatic and renal UDP-glucuronosyltransferase (UDP-GT) activities showed elevated levels especially with the 1 and 5 mg/kg doses of both congeners. Glutathione S-transferase (GST) activities did not show such a clear trend. Congeners 77 and 126 preferentially affected the P4501A enzymes but to some extent also conjugation activities.     

Short-term Effects of Ethanol Intoxication on Ascorbic Acid and Lipid Metabolism and on Drug-metabolizing Enzymes in Liver of Rats

The effects of one-time ethanol intoxication on ascorbic acid and lipid metabolism and on drug-metabolizing enzymes in liver of rats were investigated. Male Donryu rats that had been fed semi-purified feed were given 5 g/kg ethanol solution (25%, w/v) via a stomach tube and killed 16 h after intubation. The amount of ascorbic acid excreted in the urine after ethanol administration increased, but renal and adrenal concentrations of ascorbic acid decreased. The serum levels of total cholesterol, high-density-lipoprotein cholesterol, triglycerides, phospholipids, and non-esterified fatty acids were elevated in rats given ethanol, but hepatic level of total lipids, cholesterol, triglycerides, phospholipids were not. The hepatic concentrations of cytochrome P-450 and cytochrome b₅ did not increase, but this large dose of ethanol increased the activities of aminopyrine N-demethylase and cytochrome c reductase.

These results indicated that the single dose of ethanol affected the ascorbic acid and lipid metabolism of rats, and induced drug-metabolizing enzymes in their liver.     

烟草烟雾暴露对哮喘大鼠气道CCR6 mRNA及其蛋白表达的影响

目的研究烟草烟雾暴露对支气管哮喘（简称哮喘）大鼠气道chemokine receptor 6（CCR6）表达的影响,探讨吸烟加重哮喘气道炎症的免疫学机制。方法雄性Wistar大鼠40只,随机分为对照组、烟雾暴露组、哮喘组和哮喘＋烟雾暴露组,每组10只。建立哮喘大鼠模型和哮喘大鼠烟草烟雾暴露模型,采集大鼠支气管肺泡灌洗液（BALF）行白细胞计数及分类,采用逆转录-聚合酶链式反应（RT-PCR）方法及免疫组织化学法检测各组大鼠气道CCR6 mRNA及蛋白的表达。结果①哮喘组（69.0±3.5;4.1±1.0;8.9±2.0）、哮喘＋烟雾暴露组（86.7±5.2;2.2±1.0;19.0±2.8）BALF中白细胞总数、嗜酸粒细胞、中性粒细胞均高于对照组（10.1±3.8;1.3±0.7;2.2±1.1）、烟雾暴露组（47.7±6.8;0.5±0.3;2.7±1.4）（P均〈0.05）;哮喘＋烟雾暴露组BALF中白细胞总数和中性粒细胞高于哮喘组,嗜酸粒细胞低于哮喘组（P均〈0.05）。②哮喘组（8.15±0.88;0.452±0.013）、哮喘＋烟雾暴露组（15.16±0.87;0.531±0.024）CCR6 mRNA及其蛋白表达水平均明显高于对照组（1.01±0.52;0.299±0.027）、烟雾暴露组（5.55±0.54;0.442±0.018）（均P〈0.01）;哮喘＋烟雾暴露组明显高于哮喘组（均P〈0.01）。结论烟草烟雾暴露可通过促使气道CCR6 mRNA及其蛋白高表达,加重哮喘大鼠气道慢性炎症。     

Ascorbic acid deficiency decreases hepatic cytochrome P-450, especially CYP2B1/2B2, and simultaneously induces heme oxygenase-1 gene expression in scurvy-prone ODS rats

The mechanisms underlying the decrease in hepatic cytochrome P-450 (CYP) content in ascorbic acid deficiency was investigated in scurvy-prone ODS rats. First, male ODS rats were fed a diet containing sufficient ascorbic acid (control) or a diet without ascorbic acid (deficient) for 18?days, with or without the intraperitoneal injection of phenobarbital. Ascorbic acid deficiency decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial cytochrome oxidase (COX) complex IV subunit I protein, and simultaneously increased heme oxygenase-1 protein in microsomes and mitochondria. Next, heme oxygenase-1 inducers, that is lipopolysaccharide and hemin, were administered to phenobaribital-treated ODS rats fed sufficient ascorbic acid. The administration of these inducers decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial COX complex IV subunit I protein. These results suggested that the stimulation of hepatic heme oxygenase-1 expression by ascorbic acid deficiency caused the decrease in CYP content in liver.     

Effect of nicotine on glycosaminoglycan metabolism in rats.

Cigarette smoking has been established as a major risk factor for atherosclerosis and also for lung cancer. Nicotine is one of the major components of cigarette smoke which is believed to be partly responsible for the deleterious effect of cigarette smoke. There was significant alteration in the concentration of glycosaminoglycans (GAG) in rats exposed to cigarette smoke. Administration of nicotine to rats has been found to decrease many of GAG fractions in the aorta, liver and heart and increase in the lungs. The increase in GAG now observed in lung tissue in rats administered nicotine and those exposed to cigarette smoke may be involved in the increased incidence of lung cancer in smokers. Increased activity of many of GAG hydrolysing enzymes indicates increased degradation of GAG. Sulphate metabolism in the liver is also significantly altered by nicotine. Thus administration of nicotine to rats caused alteration in the metabolism of GAG which are similar to those observed on exposure of rats to cigarette smoke, indicating that nicotine content of the tobacco smoke may partly be responsible for the effect on GAG observed on exposure to cigarette smoke.     

Vitamin C prevents cigarette smoke-induced oxidative damage in vivo

Our recent in vitro results [4] indicate that cigarette smoke induces oxidation of human plasma proteins and extensive oxidative degradation of the guinea pig lung, heart, and liver microsomal proteins, which is almost completely prevented by ascorbic acid. In this paper, we substantiate the in vitro results with in vivo observations. We demonstrate that exposure of subclinical or marginal vitamin C-deficient guinea pigs to cigarette smoke causes oxidation of plasma proteins as well as extensive oxidative degradation of the lung microsomal proteins. Cigarette smoke exposure also results in some discernible damage of the heart microsomal proteins. The oxidative damage has been manifested by SDS-PAGE, accumulation of carbonyl and bityrosine, as well as loss of tryptophan and protein thiols. Cigarette smoke exposure also induces peroxidation of microsomal lipids as evidenced by the formation of conjugated dienes, malondialdehyde, and fluorescent pigment. Cigarette smoke-induced oxidative damage of proteins and peroxidation of lipids are accompanied by marked drop in the tissue ascorbate levels. Protein damage and lipid peroxidation are also observed in cigarette smoke-exposed pair-fed guinea pigs receiving 5 mg vitamin C/animal/day. However, complete protection against protein damage and lipid peroxidation occurs when the guinea pigs are fed 15 mg vitamin C/animal/day. Also, the cigarette smoke-induced oxidative damage of proteins and lipid is reversed after discontinuation of cigarette smoke exposure accompanied by ascorbate therapy. The results, if extrapolated to humans, indicate that comparatively large doses of vitamin C may protect the smokers from cigarette smoke-induced oxidative damage and associated degenerative diseases.     

DNA damage induced by cigarette smoke condensate in vitro as assayed by 32P-postlabeling. Comparison with cigarette smoke-associated DNA adduct profiles in vivo.

Cigarette smoke induces a multitude of bulky/aromatic DNA adducts in vivo as revealed by 32P-postlabeling assay. The formation of such adducts is thought to involve metabolic activation of aromatic chemicals especially polycyclic aromatic hydrocarbons (PAHs) present in tumor-initiating cigarette tar fractions, via cytochrome P450-associated monooxygenases. Because radicals are present in both the gas and particulate (tar) phase of cigarette smoke and in aqueous extracts of cigarette smoke condensate (CSC), we addressed the question as to whether cytochrome P450-independent, possibly free radical-mediated reactions may contribute, also, to formation of cigarette smoke-associated bulky DNA adducts. Rat-lung DNA was incubated with aqueous extracts of CSC in the absence of microsomes under various conditions and analyzed by 32P-postlabeling. Radioactively labeled bulky reaction products were found to accumulate in a time- and CSC concentration-dependent manner. The resulting chromatographic profiles resembled cigarette smoke-associated DNA-adduct patterns observed in vivo. Pretreatment of aqueous CSC extract with radical scavengers/reducing agents (ascorbic acid, glutathione) diminished adduct formation in a concentration-dependent manner. Adduct formation in vitro may involve oxygen-free radicals, which are known to be present in aqueous CSC extracts and could (i) attack DNA directly to produce bulky adducts, (ii) induce radical sites on DNA covalently binding CSC components, or (iii) convert CSC components to DNA-reactive electrophiles. In addition, DNA may react with direct-acting mutagens in CSC. Adduct fractions derived from in vitro and in vivo experiments showed similar chromatographic behavior, suggesting that metabolic activation as well as processes not involving metabolism lead to formation of smoking-induced bulky DNA adducts in vivo.     

The protective effects of caffeic acid phenethyl ester (CAPE) against liver damage induced by cigarette smoke inhalation in rats

The aim of this study was to investigate the histological and biochemical changes in liver of rats exposed to cigarette smoke and effects of caffeic acid phenetyl ester (CAPE) on these changes. For this purpose, 21 male Wistar rats were divided into three groups. Animals in Group I were used as control. Rats in Group II were exposed to cigarette smoke and rats in Group III were exposed to cigarette smoke and injected daily with CAPE. At the end of the 60-days experimental period, all rats were killed by decapitation and blood samples were obtained. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin levels and hepatic superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px ), malondialdehyde (MDA) contents were determined. Following routine histological procedures, liver tissue specimens were examined under a light microscope. The levels of ALT, AST, total bilirubin, SOD, GSH-Px and MDA were significantly increased in rats exposed to cigarette smoke compared with those of the controls. Light microscopic examination of liver specimens from rats exposed to cigarette smoke revealed mononuclear cell infiltration and that some of the hepatocytes had a hyperchromatic nucleus and enlarged sinusoids. The rats which were treated with CAPE along with cigarettes had partially attenuated histological changes associated with cigarette exposure. In conclusion, the damage inflicted by cigarette in the rat liver can be partially prevented by CAPE administration.     

Comparisons of Acids in Smoke of Lamina and Midrib of Flue-cured Tobacco Leaves

Acids of lamina and midrib cigarette smoke were converted into trimethylsilyl derivatives and they were analyzed with glass capillary column gas chromatography. Then compositional differences of acids between lamina and midrib cigarette smoke were discussed. The concentrations of organic acids were higher for lamina cigarette smoke than for midrib cigarette smoke. Large concentration difference were found in formic, acetic, propionic, lactic, glycolic, furoic, benzoic, phenylacetic, fumalic and m-hydroxybenzoic acid. Succinic and methylsuccinic acid were similar in lamina smoke and in midrib smoke.

A large amount of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one(amino-carbonyl reaction product) was identified for the first time in lamina smoke.     

Physiological role of the N-terminal processed P4501A1 targeted to mitochondria in erythromycin metabolism and reversal of erythromycin-mediated inhibition of mitochondrial protein synthesis

Recently, we showed that the major species of beta-naphthoflavone-inducible rat liver mitochondrial P450MT2 consists of N-terminal truncated microsomal P4501A1 (+33/1A1) and that the truncated enzyme exhibits different substrate specificity as compared with intact P4501A1. The results of the present study show that P450MT2 targeted to COS cell mitochondria by transient transfection of P4501A1 cDNA is localized inside the mitochondrial inner membrane in a membrane-extrinsic orientation. Co-expression with wild type P4501A1 and adrenodoxin (Adx) cDNAs resulted in 5-7-fold higher erythromycin N-demethylation (ERND) in the mitochondrial fraction but minimal changes in the microsomal fraction of transfected cells. Erythromycin, a potent inhibitor of bacterial and mitochondrial protein synthesis, caused 8-12-fold higher accumulation of CYP1A1 mRNA, preferential accumulation of P450MT2, and 5-6-fold higher ERND activity in the mitochondrial compartment of rat C6 glioma cells. Consistent with the increased mitochondrial ERND activity, co-expression with P4501A1 and Adx in COS cells rendered complete protection against erythromycin-mediated mitochondrial translation inhibition. Mutations that specifically affect the mitochondrial targeting of P4501A1 also abolished protection against mitochondrial translation inhibition. These results for the first time suggest a physiological function for the xenobiotic inducible cytochrome P4501A1 against drug-mediated mitochondrial toxicity.     

Selenium and Vitamin E Modulates Cigarette Smoke Exposure-Induced Oxidative Stress in Blood of Rats

Cigarette smoke contains about 5,000 chemicals that include organic and metallic compounds. The current study was undertaken to investigate the effects of selenium and vitamin E on oxidative stress-induced damage in rats exposed to cigarette smoke. Forty male rats were equally divided into four groups. The first and second groups were used as control and cigarette smoke groups, respectively. Selenium was administered to rats constituting the third group for 27 days. The Se and vitamin E combination was given to animals in fourth group for 27 days. All groups except the control, were exposed to cigarette smoke starting at the third day of the experiment and continuing for 27 days. The blood samples from all groups were taken at the end of 27 days. Plasma lipid peroxidation, triacylglycerol, and total cholesterol levels were higher in the cigarette smoke group than in the control, although erythrocytic superoxide dismutase and glutathione peroxidase activities were lower in the cigarette smoke group than in the control. The plasma lipid peroxidation, triacylglycerol, and total cholesterol levels were lower in cigarette smoke+Se+VE group than in the cigarette smoke group, although erythrocytic superoxide dismutase activity and glutathione peroxidase activity in selenium and vitamin E-administered groups were higher than in the exposed to cigarette smoke group. High-density lipoprotein-cholesterol level was not affect by selenium and vitamin E administrations. In conclusion, selenium and vitamin E seem to have protective effects on the cigarette smoke-induced blood toxicity by supporting the enzymatic antioxidant redox systems.     

The metabolism of pentachlorobenzene by rat liver microsomes: the nature of the reactive intermediates formed

Metabolism of [14C]-pentachlorobenzene by liver microsomes from dexamethasone-induced rats results in the formation of pentachlorophenol and 2,3,4,6-tetrachlorophenol as major primary metabolites in a ratio of 4:1, with 2,3,4,5- and 2,3,5,6-tetrachlorophenols as minor metabolites. The unsubstituted carbon atom is thus the favourite site of oxidative attack, but the chlorine substituted positions still play a sizable role. As secondary metabolites both para- and ortho-tetrachlorohydroquinone are formed (1.4 and 0.9% of total metabolites respectively). During this cytochrome P450-dependent conversion of pentachlorobenzene, 5-15% of the total amount of metabolites becomes covalently bound to microsomal protein. Ascorbic acid inhibits this binding to a considerable extent, indicating that quinone metabolites play an important role in the binding. However, complete inhibition was never reached by ascorbic acid, nor by glutathione, suggesting that other reactive intermediates, presumably epoxides, are also responsible for covalent binding.     

The effect of a 2-h exposure to cigarette smoke on the metabolic activation of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in A/J mice.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, induces lung adenomas in A/J mice following a single intraperitoneal (i.p.) injection. However, inhalation of mainstream cigarette smoke does not induce or promote NNK-induced lung tumors in this mouse strain purported to be sensitive to chemically-induced lung tumorigenesis. The critical events for NNK-induced lung tumorigenesis in A/J mice is thought to involve O(6)-methylguanine (O(6)MeG) adduct formation, GC-->AT transitional mispairing, and activation of the K-ras proto-oncogene. The objective of this study was to test the hypothesis that a smoke-induced shift in NNK metabolism led to the observed decrease in O(6)MeG adducts in the lung and liver of A/J mice co-administered NNK with a concomitant 2-h exposure to cigarette smoke as observed in previous studies. Following 2 h nose-only exposure to mainstream cigarette smoke (600 mg total suspended particulates/m(3) of air), mice (n=12) were administered 7.5 micromol NNK (10 microCi [5-3H]NNK) by i.p. injection. A control group of 12 mice was sham-exposed to HEPA-filtered air for 2 h prior to i.p. administration of 7.5 micromol NNK (10 microCi [5-3H]NNK). Exposure to mainstream cigarette smoke had no effect on total excretion of NNK metabolites in 24 h urine; however, the metabolite pattern was significantly changed. Mice exposed to mainstream cigarette smoke excreted 25% more 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) than control mice, a statistically significant increase (P<0.0001). Cigarette smoke exposure significantly reduced alpha-hydroxylation of NNK to potential methylating species; this is based on the 15% reduction in excretion of the 4-(3-pyridyl)-4-hydroxybutanoic acid and 42% reduction in excretion of 4-(3-pyridyl)-4-oxobutanoic acid versus control. Detoxication of NNK and NNAL by pyridine-N-oxidation, and glucuronidation of NNAL were not significantly different in the two groups of mice. The observed reduction in alpha-hydroxylation of NNK to potential methylating species in mainstream cigarette smoke-exposed A/J mice provides further mechanistic support for earlier studies demonstrating that concurrent inhalation of mainstream cigarette smoke results in a significant reduction of NNK-induced O(6)MeG adduct formation in lung and liver of A/J mice compared to mice treated only with NNK.     

Time-dependent changes in cardiovascular regulation caused by chronic tobacco smoke exposure

The purpose of this study was to determine whether chronic tobacco smoke exposure for less than 2 mo alters cardiovascular regulation. One group of male Sprague-Dawley rats was administered tobacco smoke from low-nicotine cigarettes (group A, 1 mg/cigarette) for 4-6 wk, while a second group (B) served as a sham control by receiving only puffs of room air. Reflex adjustments in mean arterial blood pressure (MAP) after bilateral common carotid occlusion (BCCO) were compared between the two groups. In the anesthetized control state, no significant difference existed for the cardiovascular parameters measured in the two groups. However, MAP increases after BCCO were significantly greater in the smoke-treated animals (P less than 0.05) compared with the sham-treated group. At 10, 20, 30, and 40 s after BCCO, MAP increases above preocclusion values were 66, 45, 42, and 38% for group A and 35, 26, 24, and 22% for group B, respectively. Additionally, the time required to reach maximum MAP after BCCO was significantly less (P less than 0.05) for the smoke-treated vs. sham-treated animals (8.5 +/- 0.2s for group A, 11.2 +/- 0.3s for group B). MAP changes during BCCO were significantly different (P less than 0.05) between the treatment groups after cervical vagotomy. It is concluded that chronic tobacco smoke exposure in experimental animals for periods as short as 4-6 wk alters the reflex regulation of the cardiovascular system.     

Membrane Phospholipid Augments Cytochrome P4501a Enzymatic Activity by Modulating Structural Conformation during Detoxification of Xenobiotics

Cytochrome P450 is a superfamily of membrane-bound hemoprotein that gets involved with the degradation of xenobiotics and internal metabolites. Accumulated body of evidence indicates that phospholipids play a crucial role in determining the enzymatic activity of cytochrome P450 in the microenvironment by modulating its structure during detoxification; however, the structure-function relationship of cytochrome P4501A, a family of enzymes responsible for degrading lipophilic aromatic hydrocarbons, is still not well defined. Inducibility of cytochrome P4501A in cultured catfish hepatocytes in response to carbofuran, a widely used pesticide around the world, was studied earlier in our laboratory. In this present investigation, we observed that treating catfish with carbofuran augmented total phospholipid in the liver. We examined the role of phospholipid on the of cytochrome P4501A-marker enzyme which is known as ethoxyresorufin-O-deethylase (EROD) in the context of structure and function. We purified the carbofuran-induced cytochrome P4501A protein from catfish liver. Subsequently, we examined the enzymatic activity of purified P4501A protein in the presence of phospholipid, and studied how the structure of purified protein was influenced in the phospholipid environment. Membrane phospholipid appeared to accelerate the enzymatic activity of EROD by changing its structural conformation and thus controlling the detoxification of xenobiotics. Our study revealed the missing link of how the cytochrome P450 restores its enzymatic activity by changing its structural conformation in the phospholipid microenvironment.     

Combined effect of alcohol and cigarette smoke on lipid peroxidation and antioxidant status in rats

The effect of long-term administration of alcohol and cigarette smoke independently and both in combination on lipid peroxidation and antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) was studied in liver, kidney, heart and lungs of albino rats. The levels of peroxidation products viz., malondialdehyde, hydroperoxides and conjugated dienes were increased in all the tissues of alcohol administered and smoke-exposed rats. Activities of SOD and CAT were decreased in alcohol-treated and alcohol and smoke combination groups, but increased in smoke-exposed group. Activities of GPx and GST have shown an increase, while concentration of reduced glutathione was found decreased in all the three groups.     

Developmental changes of serum steroids produced by cytochrome P450c17 in rat

Serum levels of 17-hydroxypregnenolone, dehydroepiandrosterone, 17-hydroxyprogesterone, and androstenedione were measured during the postnatal development of rats 1-14 weeks of age. A significant decrease in the serum levels of these steroids with increasing age was observed, using multiple regression analysis: 17-hydroxypregnenolone (beta= -1.56, S.E.= 0.25, P < 0.00001), dehydroepiandrosterone (beta= -0.43, S.E.= 0.07, P < 0.00001), 17-hydroxyprogesterone (beta= -2.51, S.E.= 0.45, P < 0.00001), and androstenedione (beta= -1.63, S.E.= 0.33, P < 0.00001). A sex-related difference was not found. The observed decline in the serum levels of the steroids was directly proportional to the previously reported decrease in mRNA expression and enzyme activity of cytochrome P450c17 in the rat liver. Yet, despite this decrease to undetectable levels in liver after 7-8 weeks, significant amounts of 17-hydroxypregnenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, and androstenedione were still observed in the rat serum. This may partly be due to the mRNA expression of cytochrome P450c17 in tissues other than the liver, such as the testis and/or duodenum, after 4 weeks of age. Serum levels of pregnenolone, progesterone, and corticosterone in the developing rats were also examined.     

Effect of cigarette smoke on the mutagenic activation of environmental carcinogens by rodent liver.

In order to assess the effect of cigarette smoke (CS) on metabolic enzymes, male hamsters and rats were exposed for two weeks to smoke produced in a Hamburg type II smoking machine. The livers were then used for Ames liquid incubation and western immunoblot assays. Mutagenic activities of seven heterocyclic amines (HCAs) in Salmonella typhimurium TA98 in the presence of rat or hamster liver S9 were elevated up to 3.7 times above controls (including sham smoke control). Enhancement of mutagenic activities of PhIP and aflatoxin B(1) was observed only in CS-exposed hamster, whereas no significant alteration of mutagenicity was observed with 2-aminofluorene, benzo[a]pyrene, and 3'-hydroxymethyl-N, N-dimethyl-4-aminoazobenzene in strain TA98 or with six N-nitrosodialkylamines in strain TA100. 7,8-Benzoflavone and/or furafylline considerably inhibited the mutagenic activation of IQ and Trp-P-1 in the presence of liver S9 from untreated hamsters and sham smoke- or CS-exposed hamsters and rats, indicating the predominant involvement of hamster cytochrome P450 (CYP) 1A enzymes in the metabolic activation of HCAs. In addition, the data suggest that CS-exposure may selectively induce hepatic CYP1A1/1A2 isoforms. Western immunoblot analyses of liver microsomes using anti-rat CYP antibodies revealed that CS-exposure increased the levels of hamster CYP1A2 (3.9-fold) and rat CYP1A2 (3.0-fold) and CYP1A1, without significant change in the levels of CYP2E1 and CYP2B and 3A isoforms in each species. The presently observed selective induction of HCA activation and CYP isozymes due to CS supports the idea that CS may contribute to enhancing effects on initiation by carcinogens which are metabolically activated by hepatic CYP1A1/1A2. In conjunction with results observed for smokers, the present findings indicate that the hamster is a good animal for studies with CS, and that cigarette smoking in combination with intake of heating protein-rich foods as a life style may markedly contribute to the human carcinogenesis by HCAs.