滴滴涕和六六六对戊巴比妥体内转化的双相影响

滴滴涕和六六六对大鼠肝脏转化戊巴比妥的作用都是双相的,卽先抑制而后刺激;对小鼠的作用,六六六是双相的,滴滴涕则只有抑制相,连续多次给与滴滴涕和六六六的所以能缩短大鼠戊巴比妥睡眠时间,除刺激药物转化酶外,部分由于肝脏重量的增加。苯巴比妥能进一步缩短滴滴涕处理大鼠的戊巴比妥睡眠时间,而对六六六处理动物则无明显影响。六六六和滴滴涕都能使大鼠尿中的维生素C排泄增加。     

Mechanisms contributing to barbiturate intolerance in rats

1. Female rats, 3 weeks after pretreatment with 200 or 400 (mg/kg)/day barbitone for 2 or 30 days, exhibited a prolonged sleeping time and a reduced awakening barbiturate brain level when challenged with either barbitone or pentobarbitone. After 3 additional weeks, the latter responses had returned, or were returning to, control values.2. Barbitone pretreatment schedules had no residual effect upon in vitro hepatic pentobarbitone-metabolizing activity measured 3 or 6 weeks later, except in one instance, when hepatic enzyme activity was significantly enhanced 3 weeks after 30 daily doses of 200 mg/kg barbitone. In this case, however, an enhanced barbiturate sleeping time, together with a reduced awakening barbiturate brain level, were observed.3. It is concluded that barbitone administered intraperitoneally in doses of 200 to 400 (mg/kg)/day for 2 or 30 days induces a non-hepatogenic intolerance to barbiturates, related to an increased sensitivity of the central nervous system to these drugs. This central intolerance is seen 3 weeks, but not 6 weeks, after pretreatment. Furthermore, this central intolerance has been observed to co-exist with an hepatic tolerance, a situation which could result in a reduced LD(50) coupled with an increase in ED(50).     

CNS tolerance to the hypnotic effect of pentobarbital in rats by injections of pentobarbital suspension.

Functional (CNS) tolerance to the hypnotic effect of barbiturates was determined in vivo by comparing the brain barbiturate level at awakening from a test dose in control rats and rats chronically treated with barbiturate. Approximately two-fold CNS tolerance to barbital was achieved by giving rats increasing concentrations of barbital in their drinking water according to trie schedule of Morgan, Pfeil and Gonzales (1977), but the tolerance was lost after the three days of withdrawal necessary to eliminate the drug from the brain. No significant CNS tolerance to the hypnotic effect of pentobarbital was developed when it was administered in the rats' food or water on various schedules. Administration of pentobarbital by daily injections of the drug in suspension, however, resulted in approximately 1.5-fold CNS tolerance to the hypnotic effect of this barbiturate in 5–10 days. Barbiturates in vitro inhibit K-stimulated ACh release from brain slices; the degree of inhibition by pentobarbital in vitro was not changed after chronic pentobarbital suspension injections in vivo.     

Blood pentobarbital concentrations during thiopental therapy

The desulfuration of thiopental to pentobarbital has previously been shown to be a relatively minor pathway of thiopental metabolism. In two cases, we observed significant conversion, resulting in blood pentobarbital concentrations up to 50 percent of total blood barbiturate (thiopental and pentobarbital) concentrations. Both patients received continuous infusions of thiopental and had present a condition (hypothermia) or drug (cimetidine) known to inhibit hepatic microsomal enzyme activity. It is suggested that inhibition of hepatic microsomal enzyme activity may prevent thiopental's metabolism to its major metabolite, a carboxylic acid analogue, and increase the amount of thiopental desulfurated to pentobarbital. Inhibition of hepatic microsomal metabolism also decreases the metabolism of pentobarbital. Until further elucidation of the causes of altered thiopental metabolism is available to identify patients more likely to have elevated concentrations of pentobarbital, monitoring of blood drug concentrations in patients receiving thiopental should include determination of both thiopental and pentobarbital concentrations.     

The influence of pure polychlorinated biphenyl compounds on hepatic function in the rat

Pure biphenyl and isomerically pure mono-, di-, tetra-, hexa-, and octachlorobiphenyls of known chemical composition were injected ip (50 mg/kg/day) into young male Wistar rats for 3 days; the animals were killed 96 hr after the last injection. The potency of the pure PCBs was compared to that of o,p′-DDT and p,p′-DDT and commercial Aroclors (1254, 1260) administered at the same concentrations. Hepatic function was assessed by pentobarbital sleeping times and in vitro assays of hepatic microsomal O-demethylase, N demethylase, aniline hydroxylase, nitroreductase, carboxylesterase and the cytoplasmic bromosulfophthalein-glutathione conjugating enzyme. Biphenyl and 4-monochlorobiphenyl did not cause induction of hepatic drug-metabolizing enzymes. Microsomal mono-oxygenases were induced by hexa- and octachlorobiphenyls and by di- and tetrachlorobiphenyls with chlorines substituted at the 3 and 4 positions. Nitroreductase and carboxylesterase activities were affected only by the highly chlorinated compounds whereas all agents, including biphenyl, caused a marked induction of the bromosulfophthalein-conjugating system.     

Possible involvement of cyclic AMP-dependent protein kinase in p,p'-DDT-induced changes in hepatic metabolism.

Administration of an acute dose of p,p-1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (p,p′-DDT) (600 mg/kg, p.o.) resulted in a significant increase in hepatic adenylate cyclase activity (40 per cent) and endogenous cyclic AMP levels (31 per cent). Although the cytosol cyclic AMP-independent protein kinase activity was only slightly affected (18 per cent), the activity of the nucleotide-dependent enzyme was significantly decreased to 74 per cent of the control values. Whereas the protein kinase activity ratio (?cyclic AMP/+cyclic AMP) of this soluble enzyme was increased, the ability of the enzyme to bind [³H]cyclic AMP in vitro was significantly decreased after pesticide administration. As observed with the soluble enzyme, maximal stimulation of the crude nuclear protein kinase (1500 g pellet) was observed 1 hr after p,p′-DDT treatment, as indicated by changes in the phosphorylation of endogenous nuclear substrates and cyclic AMP-binding capacity. Studies with lower dosages of DDT revealed that a dose as low as 100 mg/kg was sufficient to produce statistically significant alterations in the activities of both the soluble and paniculate enzymes. In most cases, doubling the dosage (200 mg/kg) resulted in greater changes in these biochemical parameters. The present study supports the concept that the DDT-induced alterations in hepatic carbohydrate metabolism may be related to an initial stimulation of the hepatic cyclic AMP-adenylate cyclase-protein kinase system.     

A model for the rapid development of dispositional and functional tolerance to barbiturates

The s.c. implantation of a 75 mg pentobarbital pellet in the back of a conscious mouse resulted in a much more rapid development of tolerance to barbiturates than that produced in mice receiving daily i.p. injections of 75 mg/kg sodium pentobarbital. Acceleration in tolerance development by pentobarbital pellet implantation was evidenced by a decrease in sleeping time after the challenge with either sodium pentobarbital or sodium barbital. The degree of hepatic microsomal drug enzyme induction after pentobarbital pellet implantation also was found to be significantly higher than that produced by the injection technique. Further studies demonstrated that the threshold for pentylenetetrazol-induced seizures was significantly reduced compared to that of the sodium pentobarbital daily injected and control groups. These studies provide an animal model for studying the mechanism of barbiturate tolerance and dependence.     

Influence of ozone on pentobarbital pharmacokinetics in mice

Previous studies have indicated that acute exposure to ambient concentrations of ozone (O3) as low as 196 micrograms/m3 (0.1 ppm) increases pentobarbital (PEN)-induced sleeping time in female mice. To elucidate potential mechanisms involved, additional studies were performed. A 3 h exposure to 9800 micrograms O3/m3 (5 ppm) did not affect brain concentrations of PEN at time of awakening, even though sleeping time was increased. Exposure for 3 h to 9800 micrograms O3/m3 (5 ppm) did not alter the pattern of brain or plasma metabolites of PEN. Pentobarbital clearance followed first-order kinetics with a one-compartment model. Mice exposed to 9800 micrograms O3/m3 (5 ppm) for 3 h had a 106% increase in the plasma half-life of pentobarbital; at 1960 micrograms O3/m3 (1 ppm) for 3 h, a 71% increase was observed. It therefore appears possible that PEN-induced sleeping time might be increased due to an decrease in hepatic metabolism of PEN.     

Effect of viral infection on drug metabolism and pesticide disposition in ducks.

The influence of duck hepatitis virus (DHV) on hepatic drug metabolism was investigated using adult mallard ducks. Mallard drakes were fed 900 ppm of DDT and were killed at various times over periods of 10 or 12 days. Pesticide analysis by electron-capture gas chromatography revealed an enhanced in vivo biotransformation of DDT in mallards infected with DHV 48 hr prior to feeding the DDT diet for 12 days. Concentrations of DDT were lower in the serum of infected ducks, while the concentration of the metabolite DDD was significantly higher (p < 0.001) in the bile of infected ducks throughout the 12-day feeding trial. The ratio of biliary DDD to DDE increased steadily in both control and DHV-treated groups, but was significantly higher (p < 0.01) among the virus-treated birds indicating a preferential induction of the microsomal dechlororeductase activity which produces DDD. Microsomal enzyme activities were generally higher in the virus-treated birds fed DDT than in noninfected controls fed DDT. The differences were most pronounced on Day 8 when the activities of all three enzymes were higher at the p < 0.05 level.     

Development of tolerance to the prolongation of Hexobarbitone sleeping time caused by cannabidiol

1 The effects of acute and subacute cannabidiol (CBD) administration on hexobarbitone sleeping time and on some constituents of the hepatic microsomal drug-metabolizing system were assessed in the mouse.

2 Acutely administered CBD prolonged sleeping time; but with subacute treatment, tolerance to the effect rapidly developed.

3 Brain hexobarbitone concentration upon awakening was unchanged by either acute or subacute CBD treatment, which suggests that neither the prolongation of sleeping time nor the tolerance is the result of a change in sensitivity of the central nervous system to the barbiturate.

4 Acute CBD treatment increased the half-time of hexobarbitone in the brain, which returned toward normal with the development of tolerance.

5 Acutely, CBD caused a 30% decrease in hepatic cytochrome P-450 level; with tolerance, the cytochrome concentration returned to normal.

6 The evidence suggests that the CBD-induced prolongation of barbiturate sleeping time and the tolerance to this effect are the result of changes in the rate of drug metabolism, which are related to changes in the amount of cytochrome P-450.

7 The effects of CBD on the hepatic microsomal drug-metabolizing enzyme system are different from those attributed to SKF 525-A and piperonyl butoxide because the cannabinoid does not decrease cytochrome P-450 quantitatively by complex formation, it does not produce a recovery overshoot in the cytochrome concentration and, finally, it does not cause an induction of the hexobarbitone-metabolizing enzymes.

     

Uterotropic activity of DDT in rats and mink and its influence on reproduction in the rat

The injection of o,p′-DDT increased uterine weights in intact immature rats, and in intact and castrate immature mink. The p,p′-isomer had only slight activity while the uterotropic activity of technical DDT was dependent upon the level of the o,p′-isomer it contained. Chronic ingestion of these compounds by rats at levels of 1 to 15 ppm in the diet did not influence fertility or fecundity in 2 successive generations. The time of vaginal opening, growth rate, and litter size was not influenced. The injection of 90 or 900 μg of p,p′-DDT or o,p′-DDT on days 1, 2, and 3 of pregnancy did not influence the number of embryos surviving to day 10 of pregnancy in the rat. However, following castration of adult female rats raised on DDT-containing diets, uterine involution was accelerated in animals receiving 15 ppm technical DDT.     

Metabolome Wide Association Study of serum DDT and DDE in Pregnancy and Early Postpartum

The advancement of high-resolution metabolomics (HRM) and metabolome-wide-association study (MWAS) enables the readout of environmental effects in human specimens. We used HRM to understand DDT-induced alterations of in utero environment and potential health effects. Endogenous metabolites were measured in 397 maternal perinatal serum samples collected during 1959-1967 in the Child Health and Development Studies (CHDS) and in 16 maternal postnatal serum samples of mice treated with or without DDT. MWAS was performed to assess associations between metabolites and p,p’-DDT, o,p’-DDT and p,p’-DDE levels, followed by pathway analysis. Distinct metabolic profiles were found with p,p’-DDT and p,p’-DDE. Amino acids such arginine had a strong association with p,p’-DDT and o,p’-DDT in both women and mice, whereas lipids and acyl-carnitine intermediates were found exclusively associated with p,p’-DDE in CHDS women indicating mitochondrial impairment. It suggests that the role of serine and fatty acid metabolism on the causal disease pathway should be examined.     

Einfluß von gewebsgespeichertem DDT auf die Wirkung von Pharmaka

Zusammenfassung Es wurde der Einfluß von akuter und chronischer DDT-Vergiftung auf die Wirkungen von Pentetrazol und Pentobarbital an Ratten untersucht.Die Krampfwirksamkeit von Pentetrazol war nach einmaliger akuter sowie nach chronischer Vergiftung nicht verändert. Erst nach dreimaliger akuter Vergiftung mit 100 mg/kg DDT oral stieg die ED₅₀ für Krämpfe signifikant von 54 auf 65 mg/kg an.Die Wirkungen von Pentobarbital wurden wesentlich stärker beeinflußt. Bei chronischer DDT-Zufuhr war die Schlafzeit nach Gabe von 30 mg/kg Pentobarbital um 80% verkürzt. Auch nach einmaliger akuter Vergiftu g mit 100 mg/kg DDT war schon nach 24 Std eine Schlafzeitabnahme um 55% zu beobachten, die nach 2 Tagen ihr Maximum mit ebenfalls 80% erreichte. Bei der weiteren Kontrolle des Vergiftungsablaufes zeigte die Schlafdauer allmählich wieder eine langsame Zunahme, war nach 70 Tagen aber immer noch um 40% vermindert. DDT-Konzentrationen im Fettgewebe und Schlafzeitverkürzung zeigen ein annähernd paralleles Verhalten.Als Ursache der Schlafzeitverkürzung wurde eine Beschleunigung des Pentobarbitalabbaus an Leberschnitten in vitro festgestellt. Bereits 1 mg/kg DDT i.p. bewirkte eine signifikante Schlafzeitverkürzung um 25%, 2 mg/kg um 50% DDT ist damit wirksamer als alle bisher bekannten Aktivatoren der oxydierenden Lebermikrosomenfermente.

---

Summary The effect of DDT poisoning on pentetrazol convulsions and pentobarbital sleeping time has been studied in rats. Both, a single acute poisoning and the chronic administration of DDT failed to alter the sensitivity towards pentetrazol convulsions. Repeated acute poisoning with an oral dose of 100 mg/kg DDT elevated the ED₅₀ for convulsions significantly from 54 to 65 mg/kg pentetrazol.A more pronounced effect of DDT was observed in pentobarbital sleeping time. In rats treated chronically with DDT the duration of sleep induced by 30 mg/kg pentobarbital was depressed to 20 percent of the control value. A single dose of DDT (100 mg/kg) lead to a reduction to 45 percent within 24 hours and to a minimal value of 20 percent within 2 days. In the further course of such DDT poisoning the duration of sleep showed a gradual increase, but after 70 days only 60 percent of the initial value was obtained. As the sleep induced by pentobarbital was restored the concentration of DDT in adipose tissue declined.The decrease in the duration of pentobarbital sleep can be explained by in vitro experiments on liver slices, showing that pretreatment with DDT caused an acceleration in the metabolism of pentobarbital. As 1 mg/kg DDT was sufficient to reduce the sleeping time to 75 percent of the control value this insecticide is more effective in activating drug metabolism in liver microsomes than any other compound.

---

---

Gefördert mit Hilfe von Forschungsmitteln des Landes Niedersachsen.     

Adaptive response of hepatic carbohydrate metabolism to oral administration of p,p'-1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane in rats

The effects of an acute dose of p,p′-1,l,1-trichloro-2,2-bis (p-chlorophenyl)ethane (p,p′-DDT) have been investigated on the activities of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-diphosphatase and glucose 6-phosphatase in rat liver. Administration of p,p′-DDT (600 mg/kg, p.o.) produced 2- to 2.5-fold stimulation of these key gluconeogenic enzymes in 5 hr, although statistically significant increases could be detected at 1 hr. Blood glucose increased as early as 0.5 hr, attained peak values at 1 hr, and then declined to reach control levels m 3–5 hr. In contrast, hepatic glycogen decreased gradually to 47 per cent of the control values in 1 hr, and was restored by 3 hr following treatment with this insecticide. Administration of p,p′-DDT to adrenalectomized rats produced similar changes in blood glucose and hepatic glycogen, suggesting that the insecticide-induced hyperglycemia and glycogenolysis may not be mediated by a release of catecholamines from the adrenals. Doseresponse studies revealed that 100 mg/kg of p,p′-DDT was the minimal amount necessary to induce statistically significant increases in the activities of hepatic pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-diphosphatase and glucose 6-phosphatase. Maximal stimulation of the four key gluconeogenic enzymes was seen generally at 5 hr when rats were treated with a 400–600 mg/kg dose of p,p′-DDT. Daily administration of small doses of p,p′-DDT (5 or 25 mg/kg) for 45 days also resulted in significant enhancement in the activities of various hepatic gluconeogenic enzymes. Actinomycin D, cycloheximide or ethionine failed to affect the basal levels of either of these hepatic enzymes, but effectively reduced the insecticide-induced increases in various enzyme activities. Treatment of adrenalectomized rats with p,p′-DDT enhanced various hepatic enzymes to a degree similar to that observed in intact animals. Furthermore, administration of triamcinolone to p,p′-DDT-treated adrenalectomized rats did not potentiate the action of the insecticide on any of the gluconeogenic enzymes examined. Our results suggest that treatment with p,p′-DDT produces marked increases in the quartet of key, rate-limiting gluconeogenic enzymes in hepatic tissue which are not mediated through a release of corticosteroids from adrenal glands.     

Effect of preexposure to kepone on hepatic mixed-function oxidases in the female rat.

The effects of preexposure of female rats to Kepone on hepatic drugmetabolizing enzymes and several other parameters of the multifunction oxidase system were investigated. Animals were exposed to 0, 50, 100, and 150 ppm Kepone in the daily ration for 16 days. There was a dose-related decline in body weight gained to 72, 55, and 22% of the controls for 50, 100, and 150 ppm Kepone, respectively. Liver weight was unaltered at all three levels of dietary Kepone. While hydroxylation of aniline, pentobarbital, and hexobarbital were all enhanced, the increase in metabolism of the latter two substrates was consistently higher than that of controls. Enhanced metabolism of pentobarbital was also evident from the dose-related decrease in the pentobarbital-induced sleeping time. Aminopyrine and ethylmorphine demethylase activities were increased three- to fourfold over the controls. Cytochrome P-450, NADPH-cytochrome c reductase, and aniline binding were all increased, suggesting that there were general increases in the intermediate steps in the electron-transfer system within the multifunction oxidase complex. Cytochrome b₅ was unaltered by Kepone and only a 100-ppm dose elicited a discernible increase in NADPH dehydrogenase activity. These effects in the female rats, along with previously published effects in the male rat, are suggestive of the potential of Kepone to modify hepatic drug-metabolizing function in animals of both sexes.     

DDT and its metabolites in leiomyomatous and normal human uterine tissue

Residues of dichlorodiphenyltrichloroethane (DDT) and its metabolites were monitored in leiomyomatous and normal human uterine tissue by gas-liquid chromatography (GLC). The metabolites detected were: 2,2-bis-(p-chlorophenyl)-1,1-dichloroethylene (p,p-DDE), 2-(o-chlorophenyl)-2-(p-chlorophenyl)-1,1,1-trichloroethane (o,p-DDT), 2,2-bis-(p-chlorophenyl)-1,1-dichloroethane (p,p-DDD) and 2,2-bis-(p-chlorophenyl)-1,1,1-trichloroethane (p,p-DDT). Total DDT ranged from 0.245 to 1.982 ppm, with a mean value of 0.845 ppm in leiomyomatous tissue. In normal human uterine tissue, total DDT ranged from 0.030 to 0.282 ppm, with a mean value of 0.103 ppm. Significantly higher levels of DDT and its metabolites in leiomyomatous tissue as compared to normal uterine tissue suggest their involvement in uterine leiomyomas. The data is discussed in the light of existing knowledge on estrogenic activity of DDT analogs and estrogeninfluenced growth of uterine leiomyomas.     

Dichlorodiphenyltrichloroethane exposure induces the growth of hepatocellular carcinoma via Wnt/β-catenin pathway

Dichlorodiphenyltrichloroethane (DDT) is a persistent organic pollutant, involved in the progression of many cancers, including liver cancer. However, the underlying mechanism(s) of DDT, especially how low doses DDT cause liver cancer, is poorly understood. In this study, we evaluated the impact of p,p′-DDT on the growth of hepatocellular carcinoma using both in vitro and in vivo models. The present data indicated that the proliferation of HepG2 cells was strikingly promoted after exposed to p,p′-DDT for 4 days. In addition, reactive oxygen species (ROS) content was significantly elevated, accompanied with inhibitions of γ-glutamylcysteine synthetase (γ-GCS) and superoxide dismutase (SOD) activities. Interestingly, the levels of β-catenin and its downstream target genes (c-Myc and CyclinD1) were significantly up-regulated, and co-treatment of NAC, the ROS inhibitor, inhibited these over-expressed proteins. Moreover, the p,p′-DDT-stimulated proliferation of HepG2 cells could be reversed after NAC or β-catenin siRNA co-treatment. Likewise, p,p′-DDT treatment increased the growth of tumor in nude mice, stimulated oxidative stress and Wnt/β-catenin pathway. Our study indicates that low doses p,p′-DDT exposure promote the growth of hepatocellular carcinoma via Wnt/β-catenin pathway which is activated by oxidative stress. The finding suggests an association between low dose DDT exposure and liver cancer growth.     

Pharmacologic response to pentobarbital in actively immunized mice.

Mice were placed on an immunization schedule known to result in the production of antibodies directed against a variety of barbiturates (antibody binding capacity = 2.71 pmole 3H-phenobarbital bound/ml undiluted serum). The pharmacologic response to barbiturate in these actively immunized mice and suitably treated controls was investigates using rotarod apparatus for monitoring CNS depression. It was found that the response to pentobarbital in actively immunized mice was decreased, as reflected by an increase in the time the mice remained on the rotarod and a shift of the dose--response curve to the right. The decreased pharmacologic response to pentobarbital was not the result of changes in levels of the hepatic drug metabolism components. Furthermore, the alteration of pharmacologic response in actively immunized mice was selective for barbiturate and did not modify the ataxia produced by administration of another depressant agent, ethanol.     

Barbiturate tolerance and hypersensitivity of arterial smooth muscle

Experiments were undertaken on rats chronically treated with pentobarbital sodium, 50 mg/kg three times per day for a period of five days, to determine whether excised aortic or venous (portal vein) smooth muscle would demonstrate any change in reactivity to catecholamines or potassium chloride. Although sleeping time was reduced 50% (indicative of tolerance to the barbiturate), mean arterial blood pressure was not affected. Aortic strips, but not portal veins, excised from barbiturate-treated animals exhibited hypersensitivity to both contractile stimulants. Potassium-depolarized calcium-depleted aortic tissue, but not portal venous smooth muscle, from the barbiturate-treated animals contracted to lower concentrations of Ca2+ than did the arterial smooth muscle from the saline-treated control rats. The present observations thus indicate that chronic barbiturate treatment in rats can induce drug supersensitivity of excitable tissue other than one associated with the central nervous system. Our results on arterial smooth muscle could help to shed light on the unexplained rises in arterial blood pressure observed in humans undergoing barbiturate withdrawal.     

Genetic differences in tolerance to ethanol: A study in UChA and UChB rats

The development of tolerance to ethanol was studied in two strains of rats, UChA (low ethanol consumer) and UChB (high ethanol consumer), by the sleeping time test. Marked tolerance (perhaps both metabolic and tissue) appeared in UCh A rats, while only a slight tissue tolerance and not a metabolic one appeared in the UChB rats, when they were offered 10% ethanol as the sole fluid during 31 days (p<0.001). In UChA, but not in the UChB rats, the chronic treatment with ethanol induced tolerance to pentobarbital as shown by the same test.