Further studies on metabolism in vivo of 3,4,3′,4′-tetrachlorobiphenyl in rats: Identification of minor metabolites in rat faeces

1. Metabolism in vivo of 3,4,3′,4′-tetrachlorobiphenyl (TCB) was investigated in male Wistar rats.

2. Five new minor metabolites in addition to two previously identified major metabolites (5-hydroxy-3,4,3′,4′-TCB and 4-hydroxy-3,5,3′,4′-TCB) were isolated as methylated derivatives from faeces of rats treated with 3,4,3′,4′-TCB, by silica gel column chromatography and subsequent preparative t.l.c.

3. Among these methylated metabolites, three were identified as dimethoxy-TCB, and one as monomethoxy-trichlorobiphenyl (TriCB), by g.l.c.-mass spectrometry. By comparison with synthetic standards they were fully identified as 2,5-dimethoxy-3,4,3′,4′-TCB, 4,4′-dimethoxy-3,5,3′,5′-TCB, 5,6-dimethoxy-3,4,3′,4′-TCB, and 4-methoxy-3,3′,4′-TriCB, respectively. The structures of these metabolites in rat faeces should therefore be 2,5-dihydroxy-3,4,3′,4′-TCB, 4,4′-dihydroxy-3,5,3′,5′-TCB, 5,6-dihydroxy-3,4,3′,4′-TCB, and 4-hydroxy-3,3′,4′-TriCB.

4. One further metabolite was isolated, which was shown to be an oxepin, existing in a state of equilibration with the 4′,5′-oxide of the major metabolite, 4-hydroxy-3,5,3′,4′-TCB, by mass and ¹H-n.m.r. spectra. On standing for several months, this metabolite isomerized to a new compound with a different g.l.c. retention time, which on methylation yielded a product identical with synthetic 4,4′-dimethoxy-3,5,3′,5′-TCB by g.l.c.-mass spectrometry. From these results this metabolite was assumed to be an oxepin, equilibrated with 4-hydroxy-4′,5′-epoxy-3,5,3′,4′-TCB.     

Tissue distribution metabolism and excretion of 2,2′,4,4′, 5-pentachlorodiphenyl ether in the rat

The tissue distribution, metabolism and excretion of ¹⁴C-2,2,4,4,5-pentachlorodiphenyl ether (PCDE) were studied in the rat. Radioactivity was distributed in all tissues examined, with the highest concentrations being found in the fat followed by the skin, liver, kidney and muscle. Most of the radioactivity found in the tissues was due to unchanged PCDE. Decay of PCDE in the blood was fitted to a four-compartment pharmacokinetic model, and the last compartment had a half-life of 5.8 days. A total of 55% and 1.3% of an orally administered dose was excreted in feces and urine, respectively, in 7 days. More than 64% of the fecal radioactivity was due to unchanged PCDE, while hydroxylated PCDE accounted for 23%.     

Effects of bilobalide on rat astrocytes in vitro

In the previous studies we found that the treatment with amyloid-β25 - 35 peptide (Aβ 25 - 35) resulted in an elevation of monoamine oxidase B (MAO-B) expression in rat astrocytes,suggesting that the upregulation of MAO-B in Aβstimulated astrocytes may play an important role in the pathogenesis of Alzheimer's disease.In present studies,we reported that bilobalide, a sesqulterpene isolated from Ginkgo biloba leaves attenuated the upregulation of MAO-B expression induced by Aβ in rat astrocytes.A significant increase in the expression of vascular endothelial growth factor was also found when the astrocytes was treated with bilobalide.The results suggest that bilobalide may play important roles in the beneficial effects of     

Effects of β-blockers on glucose and lipid metabolism

Abstract

Background:

Activation of the sympathetic nervous system (SNS) has been linked to hypertension. Beta-blockers, which decrease SNS activation via β-adrenergic receptor antagonism, are effective in lowering blood pressure and reducing cardiovascular morbidity and mortality in several conditions, including post-myocardial infarction and heart failure. Despite these clinical benefits, many physicians are reluctant to prescribe β-blockers because of perceived negative metabolic effects, including reduced glycemic control, masking of hypoglycemia, insulin resistance, and dyslipidemia.     

Comparative studies on distribution and covalent tissue binding of 2,4,2′,4′- and 3,4,3′,4′-tetrachlorobiphenyl isomers in the rat

The ¹⁴C-labeled tetrachlorobiphenyl (TCB) isomers 2,4,2,4-tetrachlorobiphenyl (2,4,2,4-TCB) and 3,4,3,4-tetrachlorobiphenyl (3,4,34-TCB) were administered orally to rats, and distribution and covalent binding were measured in several organs. Marked differences in distribution and covalent binding of the two TCBs were observed. The accumulation and retention of 2,4,2,4-TCB in adipose tissue were much higher than those of 3,4,3,4-TCB, although the level of radioactivity in the blood was consistently higher in 3,4,3,4-TCB treated rats. The radioactivity bound in covalent linkages with cellular macromolecules in several tissues was also measured. The data obtained indicated that covalent binding was higher in 3,4,3,4-TCB treated rats than in those treated with 2,4,2,4-TCB, particularly in liver and blood components. These results suggest that the two TCB isomers have different pharmacokinetic properties in rats, and the association of covalent binding with 3,4,3,4-TCB-induced toxicities might be important. In addition, we found that repeated oral dosing with the two TCB isomers caused an increase in in vitro liver microsomal generation of reactive metabolites of TCBs, indicating that the microsomal enzyme system is likely to play an important role in the in vivo covalent binding of TCB.     

Effects of methacholine,histamine and atropine on pulmonary guanosine-3′, 5′-monophosphate levels in hypersensitive mice

Summary Pulmonary levels of cGMP and cAMP in mice sensitized to methacholine and histamine with b. pertussis were examined to determine whether sensitization could be the result of an alteration in the metabolism of these cyclic nucleotides. The results presented show that in sensitized mice, methacholine raised cGMP to levels that were about double those produced without sensitization. In analogous experiments, histamine raised cGMP by approximately 100% in sensitized mice without producing significant increases in nonsensitized groups. Atropine completely blocked the cGMP rises produced by methacholine but did not eliminate those produced by histamine, thus indicating that cholinergic, but not the histaminergic elevation of cGMP involves activation of muscarinic receptors. The influence of pertussis on cAMP appeared to be opposite in direction from cGMP, i.e., a small but significant drop in cAMP levels was found following methacholine administration to sensitized, but not to nonsensitized mice. It was concluded that pertussis sensitization increases the responsiveness of the pulmonary guanylate cyclase-cGMP system to methacholine and histamine, and that the altered patterns of cGMP accumulation may contribute to the biochemical mechanism of sensitization.     

Effects of arecoline and cholinesterase inhibitors on cyclic guanosine 3′,5′-monophosphate and adenosine 3′,5′-monophosphate in mouse brain

Summary In mice, Arecoline in vivo dose-dependently increased the cGMP concentrations of the cerebellum and the cerebrum (= parts of cortex, hippocampus, hypothalamus, thalamus, striatum and midbrain) without influencing the cAMP levels. The cholinesterase inhibitors paraoxon and physostigmine caused an elevation only in cerebrum, whereas the cGMP content of the cerebellum even decreased.Pretreatment with atropine prevented the rise in cGMP levels as well as the symptoms of cholinergic stimulation elicited by arecoline or paraoxon. Diazepam reduced cGMP levels below control values and blocked the effect of arecoline, while typical symptoms due to arecoline, e.g., tremor and salivation remained unaffected. The tripeptide prolyl-leucyl-glycinamide (MIF) had no effect on either cGMP values or the peripheral signs of cholinergic stimulation elicited by arecoline.The results show that elevation of cGMP in the central nervous system caused by cholinomimetic agents can be prevented not only by cholinolytics, blocking muscarinic receptors but also by influencing other mechanisms to be discussed.     

Effects of lentinan on dendritic cell metabolism北大核心CSCD

Aim To study the effects of lentinan(LNT)on the metabolism of dendritic cells(DCs)by metabonomics, and uncover the potential mechanism of its regulation of DC function. Methods DC2.4 cells were co-incubated with LNT for 24 h, and the activity of the cells was detected by thiazolyl blue tetrazolium bromide(MTT)assay. The contents of interleukin-6(IL-6), tumor necrosis factorα(TNF-α)and interleukin-12(IL-12)in supernatant were detected by enzyme-linked immunosorbent assay(ELISA). The metabolic general changes of DC2.4 cells were detected by Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry(UPLC-QTOF/MS), and the differential metabolites were analyzed by multi-distance covariates and bioinformatics, partial least squares-discriminant analysis(PLS-DA). Finally, metabolic pathway analysis was performed by MetaboAnalyst 5.0. Results LNT did not significantly inhibit the activity of DC2.4 cells at the dose of 25～100 mg·L-1. LNT(100 mg·L-1)could significantly stimulate the secretion of IL-6, TNF-α and IL-12 in DC2.4 cells. 20 differential metabolites were identified in DC2.4 cells after being stimulated by LNT(100 mg·L-1), which involved 25 metabolic pathways including urea cycle, arginine and proline metabolism. Conclusion The regulation of LNT on DC function involves a variety of amino acid metabolism. © 2023 Publication Centre of Anhui Medical University. All rights reserved.     

Effect of desmethyldiazepam and chlordesmethyldiazepam on 3′,5′-cyclic guanosine monophosphate levels in rat cerebellum

Three different benzodiazepines (diazepam, its pharmacologically active metabolite desmethyldiazepam, and the derivative chlordesmethyldiazepam) have been compared in our study for their effects on 3,5-guanosine monophosphate (cGMP) cerebellar levels. Desmethyldiazepam and chlordesmethyldiazepam are several-fold more potent that diazepam in decreasing rat cyclic cGMP cerebellar concentrations. None of the three drugs induces detectable changes of cerebellar cyclic 3,5-adenosine monophosphate (cAMP).On the other hand, the three compounds did not modify the levels of cGMP in cerebellum of newborn rats, where Purjinje cell and dendrites lack synaptic contacts. However, injection of gamma aminobutyric acid (GABA) in the newborn is still able, as in the adult, to decrease cGMP concentration in cerebellum. Our data support the hypothesis that cGMP cerebellar concentrations may be a reliable biochemical marker of the clinical activity of benzodiazepines.     

Effect of the intraperitoneal administration of salmon-calcitonin on the “in vitro” actions of opioid agonists

• 1.1. The interaction of intraperitoneal administration of salmon-calcitonin with opioids was studied. The study was carried out using guinea pig ileum (μ and κ-opioid receptors), rabbit vas deferens (κ-opioid receptors) and mouse vas deferens (δ-opioid receptors), and selective μ, δ and κ agonists were used in the pertinent tissues.
• 2.2. The treatment with salmon-calcitonin increased, in a dose-dependent manner, the effect of U-50,488H in guinea pig ileum and rabbit vas deferens and the effects of [d-Pen², d-Pen⁵]enkephalin in mouse vas deferens.
• 3.3. The treatment with analgesic doses of salmon-calcitonin enhances the in vitro effects of κ- and δ-opioid agonists. The increase of the effectiveness of the opioid agonists may be one of the mechanisms involved on the analgesia induced by salmon-calcitonin.

     

Relationship of metabolism of 2′-, 3′- and 5′-adenine nucleotides to presynaptic inhibition of transmitter release in rat vas deferens

Summary In the isolated rat vas deferens stimulated at 0.2 Hz, a series of 2, 3-, and 5-substituted adenine nucleotides all inhibited the twitch responses, their actions being potentiated by the nucleoside transport inhibitors, HNBTGR, NBMPR and dipyridamole.The metabolism of these nucleotides was examined utilising HPLC analysis of the bathing medium after exposure to 30 M nucleoside or nucleotide for 5 min. 5-AMP, 5-ADP, 5-ATP, and NAD⁺ were all partially hydrolysed to adenosine, the relative extent of this being 5-AMP>5-ADP=5-ATPNAD⁺. However, the other nucleotides examined were not detectably converted to adenosine or to adenosine deamination products.These results indicate that the 2-, 3- and 5-substituted nucleotides studied act at a P₁-purinoceptor in rat vas deferens to inhibit neurotransmission and, with the exception of 5-AMP, 5-ADP, 5-ATP and NAD⁺, all appear to act directly at this receptor. However, the 5-adenine nucleotides (AMP, ADP and ATP) and NAD⁺ all appear to act at least partially indirectly subsequent to their hydrolysis to adenosine.Abbreviations. The following abbreviations are used ADA adenosine deaminase (EC 3.5.4.4) - 5-ADP adenosine 5-diphosphate - 2,5-ADP adenosine 2,5-diphosphate - 3 5-ADP, adenosine 3,5-diphosphate - 2-, 3 or 5-AMP adenosine 2-, 3-, or 5-monophosphate - 5-ATP adenosine 5-triphosphate - cNADP⁺ -nicotinamide dinucleotide 2,3-cyclic monophosphate - CoA coenzyme A - HNBTGR 6-(2-hydroxy-5-nitrobenzyl)-thioguanosine - NAD⁺ -nicotinamide adenine dinucleotide - NADP⁺ -nicotinamide adenine dinucleotide phosphate - NBMPR 6-(4-nitrobenzylthio)-purine riboside     

Effect of different oxygen pressures and N,N′-diphenyl-p-phenylenediamine on adriamycin® toxicity to cultured neonatal rat heart myocytes

The effect of different oxygen pressures and the antioxidant DPPD (N,N′-diphenyl-p-phenylenediamine) on Adriamycin (doxorubicin) cytotoxicity in highly purified cardiac myocytes was investigated to evaluate the involvement of free radicals in the mechanism of toxicity. Adriamycin exposure caused a time-dependent decrease in viability measured as intracellular potassium ion release or lactate dehydrogenase retention. Incubation of myocytes in 16, 172 or 834 μM oxygen during exposure to 200 μM Adriamycin for 6 hr killed 13, 42 and 56% of the cells in the respective cultures. DPPD prolonged viability in the latter two oxygen concentrations and protected against lipid peroxidation measured as production of malondialdehyde and 4-hydroxynonenal. Addition of superoxide dismutase decreased the Adriamycin-induced cell killing to 6% after a 4-hr incubation, as compared to 24% in cultures exposed to Adriamycin only. Adriamycin exposure decreased the concentration of reduced glutathione, and the toxicity of the drug was increased when glutathione reductase was inhibited by the addition of BCNU (1,3-bis-2-chloroethyl-1-nitrosourea). No significant effect on Adriamycin toxicity was observed after inhibition of glutathione synthesis by treatment with BSO (buthionine sulfoximine). It is concluded that free radicals play an important role in Adriamycin toxicity to heart myocytes, and that the cell killing mechanism is likely to be related to induction of lipid peroxidation.     

Effects of several 5′-carboxamide derivatives of adenosine on adenosine receptors of human platelets and rat fat cells

Summary The effects of several 5-carboxamide derivatives of adenosine on stimulatory (R _a) adenosine receptors of human platelets and inhibitory (R _i) adenosine receptors of rat fat cells have been compared. 5-N-Cyclopropylcarboxamidoadenosine (CPCA) and 5-N-ethylcarboxamidoadenosine (NECA) most potently inhibited ADP-induced aggregation of human platelets as shown by IC₅₀-values of 0.24 and 0.34 mol/l. 5-N-Methylcarboxamidoadenosine (MECA; IC₅₀ 0.81 mol/l) and 5-N-carboxamidoadenosine (NCA; IC₅₀ 2.1 mol/l) were less potent, whereas adenosine, 2-chloroadenosine and (-)N⁶-phenylisopropyladenosine [(-)PIA] exhibit IC₅₀-values of about 1.5 mol/l. Nearly the same rank order of potency was obtained for stimulation of adenylate cyclase activity of platelet membranes and for inhibition of [³H]NECA binding to human platelets. In order to examine the effects of the carboxamide analogues on R _i adenosine receptors of rat fat cells inhibition of lipolysis and adenylate cyclase were studied. (-)PIA was the most potent inhibitor of lipolysis as shown by an IC₅₀ of 0.5 nmol/l, followed by CPCA (IC₅₀ 1.1 nmol/l) and NECA (IC₅₀ 1.3 nmol/l), whereas MECA (IC₅₀ 17.9 nmol/l) and NCA (IC₅₀ 20.1 nmol/l) were much less potent than NECA in inhibiting lipolysis. Similar results were obtained for inhibition of adenylate cyclase activity of fat cell membranes and for competition with [³H]PIA binding to fat cell membranes. The relative potencies of the adenosine analogues at both receptor subclasses were calculated from the ratio of the IC₅₀-values for inhibition of platelet aggregation and of lipolysis. (-)PIA showed the highest selectivity for R _i receptors as indicated by a 2,900-fold lower IC₅₀ for the antilipolytic than for the antiaggregatory effect. The R _a/R _i activity ratio for NECA was about 260, for CPCA 220, for NCA 105 and for MECA 45. These results indicate that all 5-carboxamide adenosine derivatives are more potent agonists at R _i receptors than at R _a receptors. Since MECA has a higher selectivity for R _a receptors than NECA, it may be useful for the characterization of stimulatory adenosine receptors in different tissues.     

Tissue disposition,excretion and metabolism of 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99) in the male Sprague-Dawley rat

1. A disposition, metabolism and excretion study of orally administered 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) was conducted in the conventional and bile duct-cannulated male rat. 2. In the conventional rat, >50% of the radiolabelled dose was retained at 72 h, and lipophilic tissues were the preferred sites for disposition, i.e. adipose tissue, adrenals, gastrointestinal tract and skin. 3. Urinary excretion of BDE-99 was very low (<1% of dose), and glucuronidation of phenolic metabolites was suggested. 4. Biliary excretion of BDE-99 was slightly greater than observed in urine, i.e. 3.6% at 72h. 5. Over 43% of the dose in the conventional male rat and 86% in the bile duct-cannulated rat was excreted in the faeces, mainly as the unmetabolized parent compound. 6. Metabolites in bile and faeces were not conjugated. Mono- and di-hydroxylated pentabromodiphenyl ether metabolites were characterized by mass spectrometry. Two thiol metabolites were characterized in the bile. Oxidative debromination was also observed in the faecal metabolites. 7. Tissue BDE-99 was readily extractable, except for in the liver. The tissue ¹⁴C was not associated with lipids and was mainly the unmetabolized parent compound. 8. Total thyroxine (T4) plasma levels were elevated at 3 and 6 days, and returned to control levels by day 12.     

Effects of age,phenobarbital, β-naphthoflavone and dexamethasone on rat hepatic heme oxygenase

There is a wide range of change in both microsomal heme oxygenase activity and cytochrome P-450 level in the livers of rats of various ages. We tried to investigate the phases of heme oxygenase activity, both spontaneous and caused by typical MFO inducers in the lifetime of the rat. Wistar male rats aged 0.5, 1, 2, 4, 8, 12, 20 and 28 months received phenobarbital (50 mg/kg) twice, 3 and 2 days before being killed. ß-Naphthoflavone and dexamethasone were given three times: 3, 2 and 1 day before decapitation 20 mg/kg and 10 mg/kg, respectively). The highest heme oxygenase activity is observed in intact 2-week-old animals (1.16±0.038 nM/h per mg protein). Before maturity this activity decreases slightly up to the 2nd month of life. Then it stabilizes and remains virtually unchanged till the 8th month of life (1.02±0.03). Afterwards HO activity tends to increase until the 28th month of life (1.10±0.06), but does not reach the level observed in the 2-week-old animals. We have found that some typical MFO inducers can modify HO activy. While phenobarbital stimulates HO activity only in premature animals (1.42±0.056; 1.30±0.059 and 1.13±0.035, respectively in 0.5-, 1- and 2-month-old animals), ß-naphthoflavone enhances HO activity in all the groups studied. Dexamethasone, as a physiological inducer of the MFO system, modifies HO activity very characteristically. It induces this activity until the 2nd month of life and then its inducibility appears to remain unchanged. Correlations between HO activity, ALAS activity and cytochrome P-450 levels still need to be investigated to elucidate these problems.     

Effects of indometacin on joint damage in rat and rabbit

目的：研究吲哚美辛（Ｉｎｄ）对关节损伤的影响．方法：检测佐剂性关节炎大鼠（ＡＡ）非致炎侧后足爪容积，ＬＰＳ诱导腹腔巨噬细胞和关节滑膜细胞产生白细胞介素１（ＩＬ１），以及兔滑膜成纤维细胞增殖反应和软骨蛋白多糖的合成．结果：Ｉｎｄ２ｍｇ·ｋｇ－１·ｄ－１ｉｇ９ｄ，可抑制ＡＡ大鼠ｄ１８，ｄ２１，和ｄ２４继发炎症反应，但促进巨噬细胞和滑膜细胞分泌ＩＬ１．Ｉｎｄ１０μｍｏｌ·Ｌ－１体外分别促进ＩＬ１诱导兔滑膜成纤维细胞增殖反应以及抑制关节软骨蛋白多糖合成．结论：Ｉｎｄ不利于关节损伤的修复．     

Effects of N,N′-methylene-bis-acrylamide (MBA) on mouse germ cells — sperm count and morphology,and testicular pathology

The sperm count and morphology, and testicular histopathology were studied in mice over a period of 75 days following a single oral administration of 50, 100, and 200 mg/kg N.N-methylene-bis-acrylamide (MBA). With a 50 and 100 mg/kg dose, the sperm abnormality reached a maximum at 30 days, whereas the sperm count reached a minimum at 35 days. The abnormality and decrease in sperm count were both dose dependent. Following the administration of 200 mg/kg MBA, the appearance of abnormal sperm showed a diphase pattern, i.e., first at 7–15 days without any reduction of the sperm count and second at 30 days after treatment. Testicular histopathological changes showed that resting spermatocytes, succeeding leptotene and zygotene spermatocytes were either absent or reduced 1–3 days after treatment with 200 mg/kg MBA. These early histopathological changes seemed to precede both the increase in abnormal sperm and the decrease in sperm count observed 30–35 days post-treatment, and also suggested that resting spermatocytes were most sensitive to MBA exposure among various spermatogenic cells.