Fluorescence line narrowing spectrometric analysis of benzo[a]pyrene-DNA adducts formed by one-electron oxidation

Fluorescence line narrowing (FLN) was demonstrated for five benzo[a]pyrene (BP)-nucleoside adducts synthesized by one-electron oxidation of BP in the presence of guanosine, deoxyguanosine, and deoxyadenosine. The standard FLN spectra were used to prove that a major depurination adduct from the binding of BP to DNA in rat liver nuclei is 7-(benzo[a]pyren-6-yl)guanine (N7Gua). The structural characterization was performed with only 20 pg of the adduct. Metabolic activation of BP by one-electron oxidation in the horseradish peroxidase catalyzed reaction of BP with DNA (in vitro) was also investigated. The major adduct identified was 8-(benzo[a]pyren-6-yl)guanine (C8Gua).     

Evidence for distinct binding sites in the cumene hydroperoxide-dependent metabolism of benzo[a]pyrene catalyzed by cytochrome P-450

A few constitutive cytochrome P-450 isozymes in male rat liver microsomes catalyzed the metabolism of benzo[a]pyrene (BP) in cumene hydroperoxide (CHP)-dependent reactions, which produced predominantly 3-hydroxyBP and BP quinones. This process varied with the concentration of CHP. At 0.05 mM CHP, 3-hydroxyBP was the major metabolite. An increase in CHP concentration reduced 3-hydroxyBP formation but increased the level of BP quinones. This change in metabolic profile was reversed by preincubation with pyrene. Pyrene selectively inhibited quinone formation and enhanced 3-hydroxyBP formation. Naphthalene, phenanthrene and benz[a]anthracene nonspecifically inhibited total metabolism. BP binding to microsomal protein correlated with quinone formation, suggesting a common precursor reactive intermediate. BP metabolism by female rat liver microsomes also depended on CHP concentration but was much less effective than that in the male. With females, quinones were the major metabolites at all CHP concentrations, and their formation was again modulated by pyrene. These data indicate that two distinct binding sites are responsible for the formation of 3-hydroxyBP and BP quinones.     

Metabolic activation and covalent binding of benzo[a]pyrene to deoxyribonucleic acid catalyzed by liver enzymes of marine fish

Metabolic activation and covalent binding of benzo[a]pyrene (BP) to deproteinized salmon sperm DNA by supernatant fractions (10,000 g) of liver homogenates isolated from untreated, 3-methylcholanthrene (3-MC) or BP-treated starry flounder (Platichthys stellatus) and coho salmon (Oncorhynchus kisutch) were investigated. The influence of temperature, pH, time and concentrations of protein, BP, NADPH and DNA on covalent binding was investigated to obtain optimum conditions for in vitro binding (pmoles of BP equivalents bound/mg DNA/mg protein) of [³H]BP to DNA for each of the two fish species. When the supernatant fractions from untreated starry flounder were used, the covalent binding of BP to DNA was 7.5 and 2.5 times greater than the values obtained with the supernatant fractions from untreated coho salmon or rat respectively. Treatment of both fish species with 3-MC or BP resulted in a marked (10- to 53-fold) increase in the binding. Ethyl acetate-extractable metabolites formed by fish liver supernatant fractions consisted of BP dihydrodiols (4,5-, 7,8-, and 9,10-dihydrodiols), phenols (3-OH, 9-OH, and 7-OH), quinones (3,6-, 1,6- and 6,12-Q) and BP 4,5-oxide. For both fish species, BP 9,10-dihydrodiol and BP 7,8-dihydrodiol were the major metabolites comprising as much as 48–72 per cent of the total ethyl acetate-extractable metabolites; 3-hydroxy BP was also present in significant amounts. The ratio of the non-K region dihydrodiols to phenols was significantly greater for both fish species compared to rat.     

Induction of benzpyrene hydroxylase in fetal liver explants by flavones and phenobarbital

The addition of β-naphthoflavone (BNP) to fetal rat liver explants was accompanied by an increase in benzpyrene (BP) hydroxylase activity. The concentration of BNF which produced a one-half maximal induction was approximately 3 × 10^?7 M. (The term “induction” is used in a general sense to describe an elevation in enzyme activity, without specifying a genetic mechanism.) A lag of induction of 12 hr was observed when BNF was added to fresh cultures. This lag of induction was mitigated when BNF was added to 22- and 44-hr preincubated explants. Maximal induction was observed at 48–74 hr after the addition of BNF at 10^?5 M to 44-hr preincubated cultures. The early but not the later phase of BNF-mediated induction of BP hydroxylase was blocked by mercapto-(pyridethyl)-benzimidazole, an inhibitor of RNA synthesis, while both phases of induction were blocked by cycloheximide, an inhibitor of protein synthesis. The results are in accord with the hypothesis that BNF increases the de novo synthesis of BP hydroxylase in the fetal rat liver explant system. Pretreatment of fetal liver explants with pentamethoxyflavone (PMF) resulted in a decreased induction of BP hydroxylase by either BNF or 4'-bromoflavone (BrF), the latter being a much more potent inducer in this system. Since it was recently reported that the flavone derivative, PMF, was unable to induce BP hydroxylase in this system over a wide dose range, the results suggest that a common receptor interaction is required prior to the induction of BP hydroxylase by flavones.     

Influence of effectors of prostaglandin metabolism on the toxicity induced by 7-hydroxymethyl-12-methylbenz(a)anthracene in cultured rat adrenal cells

1. 7,12-Dimethylbenz(a)anthracene (DMBA) and 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA), but not benzo(a)pyrene (BP), selectively produce necrosis in the two inner zones of the rat adrenal cortex and are toxic to cultured rat adrenocortical cells. 2. The toxicity induced by 7-OHM-12-MBA in the adrenocortical cells was partially prevented by the inhibitor of the cyclooxygenase activity of prostaglandin H synthetase, indomethacin. In contrast, indomethacin did not influence the effect of BP and DMBA on these cells. 3. Two other effectors of the prostaglandin metabolism, 5,8,11,14-eicosatetraynoic acid (ETYA) and nordihydroguaiaretic acid (NDGA), as well as the anti-inflammatory steroids cortisol and dexamethasone, partially protected against, whereas arachidonic acid and bradykinin exacerbated, the cytotoxicity induced by 7-OHM-12-MBA. 4. These results indicate that prostaglandin metabolism may be involved in the necrotic mechanism of 7-OHM-12-MBA in rat adrenal cortex.     

Induction of benzpyrene hydroxylase by flavone and its derivatives in fetal rat liver explants

Fetal rat liver organ culture affords a system for the comparison of the mechanism(s) of induction^∗ of benzpyrene (BP) hydroxylase by flavones and 3-methyl-cholanthrene(3-MC). Flavone and β-naphthoflavone (BNF) were equally potent inducers at 10⁻⁵ M. 4′-halogenated flavone derivatives proved even more effective in this regard; flavanone and the naturally occuring flavone, tangeretin, were inactive. Although BP hydroxylase activity was inhibited by BNF, 3-MC or 4′-bromoflavone when added to homogenates of fetal rat liver explants, no interference by the inducer was observed under the experimental conditions employed in this study. When equal amounts of the induced and control enzyme were mixed, no less than additive enzyme activity was observed. Flavone derivatives and 3-MC appear to act by a similar mechanism in elevating BP hydroxylase, since combinations of inducers at unsaturating levels resulted in an additive effect, while at saturating levels, enzyme induction was no greater than that of the most potent agent alone.     

Central control of blood pressure by nitrergic mechanisms in organum vasculosum laminae terminalis of rat brain.

Experiments were carried out to explore the possible role played by the nitric oxide (NO) system in the organum vasculosum laminae terminalis (OVLT) of rat brain in arterial pressure regulation. Intracerebroventricular (ICV) or intra-OVLT administration of NO donors such as hydroxylamine, sodium nitro-prusside or s-nitro-acetylpenicillamine caused an up to 55 mmHg decrease in blood pressure (BP) but an increase in NO release (measured by porphyrin/nafion coated carbon fibre electrodes in combination with voltammetry) in the OVLT. In contrast, ICV or intra-OVLT administration of N(G)-nitro-L-arginine methyl ester (L-NAME; a constitutive NO synthase inhibitor) caused an up to 45 mmHg increase in BP but a fall in NO release in the OVLT. Compared with the BP responses induced by ICV injection of NO donors or NO synthase inhibitors, the OVLT route of injection required a much lower dose of NO donors or NO synthase inhibitors to produce a similar BP effect. The depressor effects induced by ICV or intra-OVLT administration of NO donors were attenuated by pretreatment with intra-OVLT injection of methylene blue (an inhibitor of guanylate cyclase), haemoglobin (a NO scavenger), L-NAME or spinal transection. On the other hand, the L-NAME-induced pressor effects were attenuated by pretreatment with intra-OVLT injection of L-arginine or spinal transection. The data suggest that activation of cyclic GMP-dependent NO synthase in the OVLT of rat brain causes cyclic GMP-dependent decreases in arterial pressure via inhibiting the sympathetic efferent activity.     

Sustained overexpression of CYP1A1 and 1B1 and steady accumulation of DNA adducts by low-dose, continuous exposure to benzo[a]pyrene by polymeric implants

Many carcinogenesis and tumorigenesis studies reported in the past several decades have relied upon bolus dose(s) of test compounds to determine their DNA damage and carcinogenic potential. The high doses are far from the human scenario where exposure is almost always to low doses and for long duration. In this study, we report a novel polymeric implant system that provides continuous ("24/7") exposure to low doses using benzo[a]pyrene (BP) as a model carcinogen. Cylindrical implants (1 cm length, 3.2 mm diameter; 10 mg BP/100 mg implant) prepared from polycaprolactone:F68 (9:1) showed controlled release in vitro for long duration. To determine the rate of release and biochemical effects in vivo, groups of female Sprague-Dawley rats received either no treatment or subcutaneous sham or BP implants (1 cm, 10% load) and were euthanized after 6, 15, 30, and 180 days; the average dose of BP by the implant route was 16.7 ± 3 μg/rat. For comparison, rats were also treated with a single bolus dose of BP intraperitoneally (10 mg/rat) and euthanized at 6, 15, and 30 days. DNA adducts analyzed by (32)P-postlabeling in the lung and liver increased steadily with time with levels reaching 31 ± 3 and 17 ± 6 adducts/10(9) nucleotides, respectively, after 25 weeks; the adduct burden in the mammary tissue initially increased but then declined with time presumably due to high cell turn over. In contrast, the bolus dose treatment showed the highest DNA adduct levels after 6 days, followed by a steady decline. The steady accumulation of tissue DNA adducts in the implant groups corroborates the sustained overexpression of CYP1A1 and 1B1, the cytochrome P450s involved in the conversion of BP to its electrophilic metabolites. In contrast, the overexpression of CYP1A1 and 1B1 resulting from the bolus dose of BP lasted only for a few days. This is the first demonstration revealing that low-dose, continuous exposure to environmental polycyclic aromatic hydrocarbons such as BP can render sustained expression of CYPs and steady accumulation of tissue DNA adducts. On the basis of our recent study in which we showed the presence of 17β-estradiol in the lung, the sustained overexpression of CYP1A1 and 1B1 due to continuous exposure to BP may increase the susceptibility to estrogen-mediated carcinogenicity.     

Comparison of benzo(a)pyrene metabolism by testicular homogenate and the isolated perfused testis of rat following 2,3,7,8-tetrachlorodibenzo-P-dioxin treatment

Benzo(a)pyrene (BP) metabolism was studied in the cell free testicular homogenate and in the isolated perfused rat testis 72 h following tetrachlorodibenzo-P-dioxin (TCDD). The BP concentration for both metabolic systems was 2 × 10^–7 M. BP metabolites were extracted from testicular homogenate, perfusate and testicular tissue and subjected to high-pressure liquid Chromatographic analysis. The ratio of various BP metabolites in the cell free homogenates ranged from 3.5 to 164 times those of the isolated perfused testis, and the total BP metabolites in the cell free system of either control or TCDD-induced testis were 16 times that of the intact isolated perfused testis. The major BP metabolites in the organic extractable phase from the isolated perfused testis and the testicular homogenate were BP dihydrodiols and BP phenols, respectively.The ratio of water soluble metabolites to organic soluble metabolites in the homogenate and the isolated perfused testis is 1.1 and 3.0 respectively. Therefore, in the intact isolated testis, water soluble BP metabolites are formed three times greater than those of the organic soluble BP metabolites, and thus suggests that specific conjugating enzyme activities in the intact testis are greater than those of the homogenates. The magnitude of various BP metabolites in either the homogenates or the isolated perfused testis of TCDD treated rats ranged from 1.4 to 2.2 times their respective controls, except 4,5-dihydroxy-4,5-dihydrobenzo(a)pyrene in the isolated perfused testis was not altered by TCDD treatment. In conclusion, the isolated perfused rat testis is metabolically active and capable of biotransforming PAH. This system better reflects metabolic capability of the intact organ in the rats than do cell free homogenate system. The isolated perfused testis system retains the integrity of the complex biological organization of tissues, cell types, and enzymes in testicular metabolism and may provide data that may aid in the prediction of germ cell mutation as well as toxicity.The Abbreviations Used are PAH polycyclic aromatic hydrocarbons - BP benzo(a)pyrene - 9,10-diol 9,10-dihydroxy-9,10-dihydrobenzo(a)pyrene - 7,8-diol 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene - 4,5-diol 4,5-dihydroxy-4,5-dihydrobenzo(a)pyrene - 3-OH 3-hydroxybenzo(a)pyrene - 9-OH 9-hy-droxybenzo(a)pyrene - 7-OH 7-hydroxybenzo(a)pyrene - 12-OH 12-hydroxybenzo(a)pyrene - 1,6-quinone benzo(a)pyrene-1,6-dione - 3,6-quinone benzo(a)pyrene 3,6-dione - 6,12-quinone benzo(a)pyrene 6,12-dione - DMBA 7,12-dimethylbenzanthracene - DMN dimethylnitrosamine - 7,8-diol 9,10-epoxide 5,7-t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene - HPLC high pressure liquid chromatography - TCDD 2,3,7,8-tetrachlorodibenzo-P-dioxin - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid - NADP⁺ nicotinamide adenine dinucleotide - AHH aryl hydrocarbon hydroxylase - EH epoxide hydrolase - GSH-T glutathione transferase - HPRT hypoxanthine phosphoribosyltransferase     

Inhibition of poly (ADP-ribose) synthetase by gene disruption or inhibition with 5-iodo-6-amino-1,2-benzopyrone protects mice from multiple-low-dose-streptozotocin-induced diabetes.

Activation of poly(ADP-ribose) synthetase (PARS, also termed polyADP-ribose polymerase or PARP) has been proposed as a major mechanism contributing to beta-cell destruction in type I diabetes. In the present study, we have investigated the role of PARS in mediating the induction of diabetes and beta-cell death in the multiple-low-dose-streptozotocin (MLDS) model of type I diabetes. Mice genetically deficient in PARS were found to be less sensitive to MLDS than wild type mice, with a lower incidence of diabetes and reduced hyperglycemia. A potent inhibitor of PARS, 5-iodo-6-amino-1,2-benzopyrone (INH(2)BP), was also found to protect mice from MLDS and prevent beta-cell loss, in a dose-dependent manner. Paradoxically, in the PARS deficient mice, the compound increased the onset of diabetes. In vitro the cytokine combination; interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma inhibited glucose-stimulated insulin secretion from isolated rat islets of Langerhans and decreased RIN-5F cell viability. The PARS inhibitor, INH(2)BP, protected both the rat islets and the beta-cell line, RIN-5F, from these cytokine-mediated effects. These protective effects were not mediated by inhibition of cytokine-induced nitric oxide formation. Inhibition of PARS by INH(2)BP was unable to protect rat islet cells from cytokine-mediated apoptosis. Cytokines, peroxynitrite and streptozotocin were all shown to induce PARS activation in RIN-5F cells, an effect suppressed by INH(2)BP. The present study provides evidence for in vivo PARS activation contributing to beta-cell damage and death in the MLDS model of diabetes, and indicates a role for PARS activation in cytokine-mediated depression of insulin secretion and cell viability in vitro.     

Alterations of pulmonary benzo[a]pyrene metabolism by reactive oxygen metabolites.

Superoxide anion radical and hydrogen peroxide (H2O2) are reactive oxygen metabolites which are thought to be involved in oxidant-induced lung injuries. Therefore, we studied their effects on the pulmonary metabolism of benzo[a]pyrene (BP) in rat lung microsomes. The microsomes were incubated with xanthine and xanthine oxidase to generate superoxide anion (effects verified with superoxide dismutase) or H2O2 and then the products formed during the metabolism of BP were measured. Both oxygen metabolites inhibit BP hydroxylase activity, i.e., the production of 3- and 9-hydroxybenzo[a]pyrene (phenols) in a concentration-dependent manner. The phenols account for approximately 75% of metabolite formation and are the major products of BP metabolism. Two components of the monooxygenase system responsible for BP metabolism, cytochrome P-450 and NADPH-cytochrome P-450 reductase, are also inhibited by the two oxygen metabolites in a similar manner. Superoxide anion is more effective than H2O2 in the inhibition of both BP hydroxylase and the monooxygenase components. Neither oxygen metabolite has any effect on the formation of minor metabolites of benzo[a]pyrene, i.e., BP-quinones and BP-dihydrodiols. These are the BP metabolites thought to produce toxic effects and which may lead to the formation of carcinogens and/or mutagens. The results of all these experiments suggest that exposure of lung microsomes to oxygen metabolites can lead to a slowing of overall BP metabolism and the increased accumulation of potentially toxic BP metabolites.     

Identification and quantitation of benzo[a]pyrene-DNA adducts formed by rat liver microsomes in vitro.

The two DNA adducts of benzo[a]pyrene (BP) previously identified in vitro and in vivo are the stable adduct formed by reaction of the bay-region diol epoxide of BP (BPDE) at C-10 with the 2-amino group of dG (BPDE-10-N2dG) and the adduct formed by reaction of BP radical cation at C-6 with the N-7 of Gua (BP-6-N7Gua), which is lost from DNA by depurination. In this paper we report identification of several new BP-DNA adducts formed by one-electron oxidation and the diol epoxide pathway, namely, BP bound at C-6 to the C-8 of Gua (BP-6-C8Gua) and the N-7 of Ade (BP-6-N7Ade) and BPDE bound at C-10 to the N-7 of Ade (BPDE-10-N7Ade). The in vitro systems used to study DNA adduct formation were BP activated by horseradish peroxidase or 3-methylcholanthrene-induced rat liver microsomes, BP 7,8-dihydrodiol activated by microsomes, and BPDE reacted with DNA. Identification of the biologically-formed depurination adducts was achieved by comparison of their retention times on high-pressure liquid chromatography in two different solvent systems and by comparison of their fluorescence line narrowing spectra with those of authentic adducts. The quantitation of BP-DNA adducts formed by rat liver microsomes showed 81% as depurination adducts: BP-6-N7Ade (58%), BP-6-N7Gua (10%), BP-6-C8Gua (12%), and BPDE-10-N7Ade (0.5%). Stable adducts (19% of total) included BPDE-10-N2dG (15%) and unidentified adducts (4%). Microsomal activation of BP 7,8-dihydrodiol yielded 80% stable adducts, with 77% as BPDE-10-N2dG and 20% of the depurination adduct BPDE-10-N7Ade. The percentage of BPDE-10-N2dG (94%) was higher when BPDE was reacted with DNA, and only 1.8% of BPDE-10-N7Ade was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)     

乌菊降压丸药效学实验

目的 :对乌菊降压丸的药理作用进行实验研究。方法 :以正常血压大鼠和自发性高血压大鼠 (SHR )的血压和心率为动物模型 ,观察乌菊降压丸的药效作用。空白对照组给予相应量的0 5 %羧甲基纤维素钠 ;阳性对照组给予牛黄降压丸2g/kg;实验组给予乌菊降压丸 ,高、中、低剂量分别为1 2、0 6、0 2g/kg。灌胃给药 ,qd ,连续15d。分别观察并记录给药后10、20、30、45、60、90、120、240min时的血压和心率变化。结果 :乌菊降压丸高、中剂量对SHR分别在20、30min起效 ,血压开始下降 ,心率开始减慢 ,分别维持3h和1h ,4h和2h恢复原来水平。结论 :乌菊降压丸对正常血压大鼠的血压和心率无明显影响 (P>0 05) ,但有一定降低趋势 ;对SHR连续给药15d后具有明显降压作用和减慢心率的作用 (P<0 05) ;高剂量组有较好的降压效果     

Effects of bepridil hydrochloride on cardiocirculatory dynamics, coronary vascular resistance, and cardiac output distribution in normal, conscious rats

The purpose of this study was to characterize the cardiocirculatory effects of bepridil hydrochloride (BP) in the normal, conscious rat. Animals were instrumented under halothane anesthesia for right atrial, left ventricular, arterial, and venous pressure recordings. The radioactive-microsphere technique was used to measure regional blood flow and cardiac output before (control) and during intravenous (i.v.) infusion of either BP at three dosage levels (3.0, 6.0, 12.0 mg/kg) or vehicle (VH) at infusion rates matching those of the BP protocol (0.0408 ml/min). The predominant effects of BP (cumulative dose = 9.0 mg/kg i.v.) in the conscious rat were reduced coronary vascular resistance and heart rate. BP showed selectivity for the coronary circulation since systemic vascular resistance was not significantly reduced until a cumulative i.v. dosage of 21.0 mg/kg was administered. BP had few effects on other regions of the peripheral circulation. BP (21 mg/kg) reduced blood flow and increased vascular resistance in the arterial circulations of four of six skeletal muscles studied although opposite effects occurred in two of six muscles studied. BP had no significant effect on blood flow or vascular resistance in the other major arterial circulations. The results of this study show that BP is a selective coronary vasodilator that also reduces the primary indices of myocardial oxygen demand. These results suggest that the clinical therapeutic antianginal efficacy of BP occurs through a combined effect to increase myocardial oxygen supply and to reduce myocardial oxygen demand.     

CV3988 inhibits in vivo platelet aggregation induced by PAF-acether and collagen

Platelet activating factor (PAF-acether) was shown to cause a fall in the circulating platelet count and blood pressure (BP) in anaesthetised rabbits. CV3988 caused a dose-dependent inhibition of these responses to a low dose of PAF-acether (150 ng · kg⁻¹). CV3988 itself was found to cause a fall in both BP and platelet count in vivo. Collagen (40 μg · kg⁻¹) i.v. caused sudden death in rabbits and pretreatment with CV3988 (5 mg · kg⁻¹) caused a 62% inhibition of the platelet count response to collagen without significantly increasing the survival rate. In the rat, collagen (40 μg · kg⁻¹) was not lethal and CV3988 caused a dose-dependent inhibition of the fall in platelet count due to collagen, but this action was short-lived. CV3988 also caused agonist actions in the rat. These results show that CV3988 inhibits the effects of PAF-acether in vivo and suggests that PAF-acether may play a role in mediating collagen-induced platelet aggregation in vivo.     

Effects of cigarette smoke on rat lung and liver ornithine decarboxylase and aryl hydrocarbon hydroxylase activities and lung benzo(a)pyrene metabolism

The response of rat lung and liver ornithine decarboxylase (ODC) and aryl hydrocarbon hydroxylase (AHH) activities and lung benzo(a)pyrene (BP) metabolism was studied after exposing the rats to cigarette smoke. A close analysis of the time curves for ODC and AHH activities in rat lung and liver after a single exposure to cigarette smoke resulted in no clear correlation between the two parameters. Prolonged treatment (10 days) produced an increase in pulmonary ODC activity; hepatic ODC activity was unaffected. 10-day treatment was ineffective in raising AHH activity above values observed after a single treatment. BP metabolism, as determined in isolated perfused lungs by the appearance of organic- and water-soluble metabolites in the perfusion medium, the amount of covalently bound metabolites in lung tissue and the disappearance of unchanged 3-H BP from the perfusate, was markedly increased in response to cigarette smoke treatment. The data presented indicate that induction of AHH activity and increased metabolism of BP do not necessarily require a pre-existing increase in ODC activity.     

Cardio-respiratory changes and mortality in the conscious rat induced by (+)- and (+/-)-anatoxin-a.

Anatoxin-a (AnTx-a) is a potent nicotinic cholinergic receptor agonist. The relative potencies of the (+)-AnTx-a and the racemic mixture (+/-)-AnTx-a were investigated in the conscious rat by comparing their effects on mean arterial blood pressure (BP), heart rate (HR), blood oxygen and carbon dioxide pressures (pO2 and pCO2, respectively), acid-base balance (pH) and mortality. The present experiments show that while both forms of AnTx-a produce dose-dependent increases in BP and decreases in HR, (+)-AnTx-a is about 10-fold more potent than the optically inactive isomer. (+)-AnTx-a was also 6-fold more potent than (+/-)-AnTx-a in producing severe hypoxemia, and more than 4-fold as potent as the (+/-)-AnTx-a in producing significant hypercapnia accompanied with severe acidosis. The approximate median lethal dose (LD50) of (+)-AnTx-a was about 5-fold less than that of (+/-)-AnTx-a. We conclude that (+)-AnTx-a is more potent than the (+/-)-AnTx-a racemic mixture in causing detrimental cardio-respiratory changes and therefore increased mortality in the rat.     

Influence of effectors of prostaglandin metabolism on the toxicity induced by 7-hydroxymethyl-12-methylbenz(a)anthracene in cultured rat adrenal cells

1. 7,12-Dimethylbenz(a)anthracene (DMBA) and 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA), but not benzo(a)pyrene (BP), selectively produce necrosis in the two inner zones of the rat adrenal cortex and are toxic to cultured rat adrenocortical cells.

2. The toxicity induced by 7-OHM-12-MBA in the adrenocortical cells was partially prevented by the inhibitor of the cyclooxygenase activity of prostaglandin H synthetase, indomethacin. In contrast, indomethacin did not influence the effect of BP and DMBA on these cells.

3. Two other effectors of the prostaglandin metabolism, 5,8,11,14-eicosatetraynoic acid (ETYA) and nordihydroguaiaretic acid (NDGA), as well as the anti-inflammatory steroids cortisol and dexamethasone, partially protected against, whereas arachidonic acid and bradykinin exacerbated, the cytotoxicity induced by 7-OHM-12-MBA.

4. These results indicate that prostaglandin metabolism may be involved in the necrotic mechanism of 7-OHM-12-MBA in rat adrenal cortex.     

Comparative mutagenicity tests in the Salmonella/microsome assay with rat and woodchuck S9 preparations

The Salmonella mutagenicity assay was utilized to compare the hepatic S9 fractions from untreated and 3-methylcholanthrene (MC) induced woodchucks with Aroclor 1254 induced rats. Three known promutagens, benzo[a]pyrene (BP), 7,12-dimethylbenz[a]anthracene (DMBA), and 2-aminofluorene (AF) were tested at 5 concentrations with the strain TA100 against 3 levels of S9 fraction. Both woodchuck S9 fractions were as effective as the rat S9 in activating BP and both were more effective than the rat S9 in activating DMBA. Untreated woodchuck S9 was also as effective as rat S9 in activating AF. The protein content of the S9 fraction did not differ significantly between rats and woodchucks, but the P-450 content of the rat S9 was approximately 3.5 times that of woodchuck.     

Telemetric monitoring of adrenocorticotrophin-induced hypertension in mice

1. The mouse is the animal of choice for studies involving genetic manipulation and transgenic and knockout mice are valuable tools for physiological studies. We have studied adrenocorticotrophin (ACTH)- and steroid-induced hypertension in both rat and humans. The aim of the present study was to develop a model of ACTH-induced hypertension in the mouse and to assess a chronically implanted telemetric device for measurement of blood pressure (BP). 2. Male Swiss Outbred and Quackenbush Swiss (QS) mice (35-45 g) were implanted with TA11PA-C20 BP devices (Data Sciences International, St Paul, MN, USA) under isoflurane anaesthesia. Seven to 10 days later, mice were monitored telemetrically for baseline BP for 4 days. Mice were then randomly allocated to: (i) sham treatment with normal saline s.c.; or (ii) ACTH at 500 microg/kg per day, s.c. Mice were monitored 24 h/day for 10 days. 3. Sham treatment (n = 7) did not affect BP (114 +/- 2/84 +/- 1 to 115 +/- 2/84 +/- 1 mmHg; P = NS). Adrenocorticotrophin treatment (n = 5) raised BP from 112 +/- 7/82 +/- 4 to 138 +/- 3/104 +/- 4 mmHg, which was significantly different from sham treatment (P = 0.0021 for systolic BP; P < 0.0001 diastolic BP). The increase in BP with ACTH was comparable with that seen in previous studies in humans, sheep and rat. Sham and ACTH-treated animals each lost 3% bodyweight. 4. Administration of ACTH (500 microg/kg per day) raises BP in two strains of mice, measured using a telemetry system. This model will allow the selective use of transgenic and/or knockout mice to further elucidate the mechanism of ACTH- and steroid-induced hypertension.