Determination of norcantharidin in mouse tissues by liquid chromatography coupled to tandem mass spectrometry and its tissue distribution study

The purpose of this study is to determine the concentrations of norcantharidin (CAS NO: 5442-12-6) in mouse tissues and investigate its tissue distribution after intragastric administration of disodium norcantharidate solution. A highly sensitive and specific liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated, using ribavirin (CAS NO: 36791-04-5) as the internal standard (IS). Norcantharidin and IS were extracted from 0.3 mL tissue homogenates using protein precipitation with acetone under acid condition. The analyte was separated on a C18 reverse phase column and analyzed by MS/MS in the multiple reaction monitoring (MRM) mode using ESI with positive ionization, m/z 169→123 for norcantharidin and m/z 267→135 for IS. The developed method was validated over a linear range of concentrations 0.01~5 μg·mL - 1 in liver, lung, kidney, stomach, small intestine, uterus and testis, 0.005~0.5 μg·mL - 1 in heart, spleen and brain, the correlation coefficients (r2) were between 0.9918 and 0.9976. The tissue distribution study result was as follows: The AUC0-t of norcantharidin in tissues was in the order as follows: small intestine, stomach, uterus, kidney, testis, liver, lung, spleen, heart, brain.     

Efficacy of diphenyl diselenide against cerebral and pulmonary damage induced by cadmium in mice

This study was designed to examine if diphenyl diselenide (PhSe)(2), an organoselenium compound, attenuates pulmonar and cerebral oxidative stress caused by sub-chronic exposure to CdCl(2). Male adult Swiss albino mice received CdCl(2) (10 micromol/kg, subcutaneously), 5 times/week, for 4 weeks. (PhSe)(2) (10 micromol/kg or 20 micromol/kg, orally) was given concomitantly with CdCl(2) to mice. A number of toxicological parameters in lung and brain of mice were examined including delta-aminolevulinic acid dehydratase (delta-ALA-D), superoxide dismutase (SOD) and catalase activities, lipid peroxidation, non-protein thiols (NPSH) and ascorbic acid content. Na(+),K(+)-ATPase activity, acetylcholinesterase (AChE) activity, [(3)H]glutamate uptake and [(3)H]glutamate release were also carried out in brain. Cadmium concentration and histopathological analysis were carried out in lung tissue. (PhSe)(2) at the dose of 20 micromol/kg protected the inhibition of delta-ALA-D, SOD and CAT activities, the reduction of vitamin C content and the increase of lipid peroxidation levels caused by CdCl(2) in lungs. At 10 micromol/kg, (PhSe)(2) protected cerebral AChE and CAT activities inhibited by CdCl(2). There were no histopathological alterations in the lung of mice after CdCl(2) exposure. The pulmonary cadmium concentration was higher (2.8-fold) in the group exposed to CdCl(2) than in control mice. (PhSe)(2) at dose of 20 micromol/kg reduced cadmium concentration towards the control level. The results suggest that oral administration of (PhSe)(2) attenuated the oxidative damage induced by CdCl(2) in lung and brain of mice.     

Tissue Distribution of Indinavir Administered as Solid Lipid Nanocapsule Formulation in <Emphasis Type="Italic">mdr1a</Emphasis> (+/+) and <Emphasis Type="Italic">mdr1a</Emphasis> (−/−) CF-1 Mice

Purpose Due to protease inhibitor (PI) efflux transport by P-glycoprotein (P-gp), insufficient PI concentrations result in low ongoing HIV replication in the so-called virus sanctuaries (brain and testes). The aim of the present study was to evaluate indinavir-loaded nanocapsules (Ind-LNC) including Solutol^? HS15, an excipient reported to possess in vitro P-gp inhibiting properties, as a means to improve indinavir distribution into brain and testes of mice. Methods Normal mdr1a (+/+) or P-gp-deficient mdr1a (−/−) CF-1 mice were dosed with Ind-LNC (10 mg indinavir/kg, i.v.). At 30 min postadministration, indinavir was determined in plasma, brain, testes, as well as in kidneys, liver, and heart by LC-MS/MS, and tissue/plasma concentration ratios were calculated. Results were compared with those of control groups that received an indinavir solution (Ind-Sol). Results Using Ind-Sol, ratios were 21.3- and 3.3-fold higher in brains and testes of mdr1a (−/−) mice than of mdr1a (+/+) mice, respectively, whereas in the other organs ratios were not significantly different between the two substrains. When Ind-LNC was used, a similar [mdr1a (−/−) vs. mdr1a (+/+) mice] trend was observed. Moreover, ratios were found to be significantly increased (1.9-fold increase in average) in most organs (brain and testes in particular) with Ind-LNC compared to Ind-Sol, regardless of the substrain used. Conclusions In agreement with previous works, P-gp governs at least in part indinavir uptake into brain and testes. LNC formulation increased indinavir uptake in brain and testes by mechanisms other than, or additional to, P-gp inhibition.     

Diquat induces renal proximal tubule injury in glutathione reductase-deficient mice

Reactive oxygen species (ROS) have been associated with many human diseases, and glutathione (GSH)-dependent processes are pivotal in limiting tissue damage. To test the hypothesis that Gr1(a1Neu) (Neu) mice, which do not express glutathione reductase (GR), would be more susceptible than are wild-type mice to ROS-mediated injury, we studied the effects of diquat, a redox cycling toxicant. Neu mice exhibited modest, dose- and time-dependent elevations in plasma alanine aminotransferase (ALT) activities, 126+/-36 U/l at 2 h after 5 micromol/kg of diquat, but no ALT elevations were observed in diquat-treated C3H/HeN mice for up to 6 h after 50 micromol/kg of diquat. Histology indicated little or no hepatic necrosis in diquat-treated mice of either strain, but substantial renal injury was observed in diquat-treated Neu mice, characterized by brush border sloughing in the proximal tubules by 1 h and tubular necrosis by 2 h after doses of 7.5 micromol/kg. Decreases in renal GSH levels were observed in the Neu mice by 2 h post dose (3.4+/-0.4 vs 0.2+/-0.0 micromol/g tissue at 0 and 50 micromol/kg, respectively), and increases in renal GSSG levels were observed in the Neu mice as early as 0.5 h after 7.5 micromol/kg (105.5+/-44.1 vs 27.9+/-4.8 nmol/g tissue). Blood urea nitrogen levels were elevated by 2 h in Neu mice after doses of 7.5 micromol/kg (Neu vs C3H, 32.8+/-4.1 vs 17.9+/-0.3 mg/dl). Diquat-induced renal injury in the GR-deficient Neu mice offers a useful model for studies of ROS-induced renal necrosis and of the contributions of GR in defense against oxidant-mediated injuries in vivo.     

Quantitative determination of total methamphetamine and active metabolites in rat tissue by liquid chromatography with tandem mass spectrometric detection

High-throughput liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) methodology for the determination of methamphetamine (METH), amphetamine (AMP), 4-hydroxymethamphetamine (4-OH-METH), and 4-hydroxyamphetamine (4-OH-AMP) was developed and validated using simple trichloroacetic acid sample treatment. The method was validated in rat serum, brain, and testis. Lower limits-of-quantitation (LOQ) for METH and AMP were 1 ng x mL(-1) using positive ion electrospray tandem mass spectrometry (MS/MS). The accuracy of the method was within 25% of the actual values over a wide range of analyte concentrations. The within-assay precision was better than 12% (coefficient of variation). The method was linear over a wide dynamic range (0.3-1000 ng x mL(-1)). Quantitation was possible in all 3 matrices using only serum standards because of minimal matrix-associated ion effects or the use of an internal standard. Finally, the LC-MS/MS method was used to determine serum, brain, and testis METH and AMP concentrations during a subcutaneous infusion (5.6 mg kg(-1) day(-1)) of METH in rats. Concentrations of 4-OH-AMP and 4-OH-METH were below the LOQ in experimental samples. The bias introduced by using serum calibrators for the determination of METH and AMP concentrations in testis and brain was less than 8% and insignificant relative to the interanimal variability.     

The metabolism of clomethiazole in gerbils and the neuroprotective and sedative activity of the metabolites

A single dose of clomethiazole (600 micromol kg(-1) i.p.) has previously been shown to be neuroprotective in the gerbil model of global ischaemia. In gerbils, clomethiazole (600 micromol kg(-1)) injection produced a rapid appearance (peak within 5 min) of drug in plasma and brain and similar clearance (plasma t(1/2): 40 min) from both tissues. The peak brain concentration (226+/-56 nmol g(-1)) was 40% higher than plasma. One major metabolite, 5-(1-hydroxyethyl-2-chloro)-4-methylthiazole (NLA-715) and two minor metabolites 5-(1-hydroxyethyl)-4-methylthiazole (NLA-272) and 5-acetyl-4-methylthiazole (NLA-511) were detected in plasma and brain. Evidence suggested that clomethiazole is metabolized directly to both NLA-715 and NLA-272. Injection of NLA-715, NLA-272 or NLA-511 (each at 600 micromol kg(-1)) produced brain concentrations respectively 2.2, 38 and 92 times greater than seen after clomethiazole (600 micromol kg(-1)). Clomethiazole (600 micromol kg(-1)) injected 60 min after a 5 min bilateral carotid artery occlusion in gerbils attenuated the ischaemia-induced degeneration of the hippocampus by approximately 70%. The metabolites were not neuroprotective at this dose. In mice, clomethiazole (600 micromol kg(-1)) produced peak plasma and brain concentrations approximately 100% higher than in gerbils, drug concentrations in several brain regions were similar but 35% higher than plasma. Clomethiazole (ED(50): 180 micromol kg(-1)) and NLA-715 (ED(50): 240 micromol kg(-1)) inhibited spontaneous locomotor activity. The other metabolites were not sedative (ED(50) >600 micromol kg(-1)). These data suggest that the neuroprotective action of clomethiazole results from an action of the parent compound and that NLA-715 contributes to the sedative activity of the drug. British Journal of Pharmacology (2000) 129, 95 - 100     

Sub-chronic administration of diphenyl diselenide potentiates cadmium-induced testicular damage in mice

Sub-chronic cadmium (Cd) exposure causes testicular damage in mice. The mode of action may involve oxidative stress and especially lipid peroxidation. The present study has monitored the pathogenesis of testicular damage during sub-chronic Cd exposure and has evaluated the potential protective effect of antioxidant therapy with diphenyl diselenide (PhSe)(2). Male mice were dosed with 2.5 mg/kg CdCl(2) (2.5 mg/kg) with or without (PhSe)(2) (5 micromol/kg) at 30 min post-exposure using a model of five weekly subcutaneous injections. Histological evaluation of the testis was performed across a 4 week test period. Animals exposed to CdCl(2) and CdCl(2) plus (PhSe)(2) displayed a reduction in body weight gain and testicular weight. Progressive damage and histolopathological changes in the testis were not remedied with, but rather were potentiated by, (PhSe)(2) therapy. We conclude that (PhSe)(2) enhances testicular injury in an animal model for sub-chronic Cd exposure mice.     

Central nervous system distribution kinetics of indinavir in rats

The central nervous system (CNS) distribution kinetics of indinavir were extensively evaluated using a combinational in-vivo model comprising the integration plot method (a single-passage approach) and neuropharmacokinetic method (a multiple-passage approach). A 5 mg kg(-1) dose of indinavir was administered intravenously to rats. Blood and cerebrospinal fluid (CSF) samples and whole brain were collected from the animals at specified time points and the drug concentration in each sample was determined using a high-performance liquid chromatography method. For the neuropharmacokinetic study, the simultaneous plasma, CSF and brain concentrations were fitted to an integrated model, which resulted in the estimation of the influx (K(in)) and efflux (K(out)) rate constants of the drug to/from CSF and brain parenchyma. The integration plot method involved plotting the brain-plasma or CSF-plasma concentration ratios (K(p, app)) against AUC(0-->t)/C(p(t)), and estimating the uptake clearance of the drug by brain/CSF from the slope of the initial linear portion of the plot. The K(in) and K(out) values of the drug to/from CSF were estimated to be 2.42 x 10(-2) and 13.26 x 10(-2)min(-1), respectively, and the corresponding values for brain parenchyma were 1.02 x 10(-2) and 1.32 x 10(-2) min(-1), respectively. The uptake clearances of indinavir by CSF and brain parenchyma were 8.89 and 8.38microL min(-1)g(-1), respectively. The permeability surface area products of the drug for the blood-brain barrier and blood-CSF barrier were estimated as 1.05 x 10(-2) and 2.45 x 10(-2) mLmin(-1)g(-1), respectively. The estimated kinetic parameters indicated limited CNS entry of the drug because of the limited blood-brain barrier permeability and the efficient drug efflux from CNS, particularly from CSF.     

Differential in vivo effects of H3 receptor ligands in a new mouse dipsogenia model

The selective H(3) receptor agonist (R)-alpha-methylhistamine [(R)-alpha-MeHA] stimulates drinking in the adult rat. In the present study, we investigated the role of the H(3) receptor in mediating this behavior in a new dipsogenia model using the CD-1 mouse. In addition, the putative inverse agonists ciproxifan, thioperamide and clobenpropit; the reported antagonist (1R,2R)-4-[2-(5,5-dimethylhex-1-ynyl)cyclopropyl]imidazole (GT-2331); and the putative neutral antagonist/weak partial agonist proxyfan were evaluated for possible differences in pharmacological activity in this new model. Water intake increased over baseline in a dose-related manner following intraperitoneal administration of 80, 160 or 240 micromol/kg (R)-alpha-MeHA, but this effect was dependent on age (P30相似文献   

Determination of indinavir, a HIV-1 protease inhibitor, in human plasma using ion-pair reversed-phase high-performance liquid chromatography.

Indinavir is widely prescribed as a component of potent antiretroviral therapy for the treatment of HIV-1 infection. Because virologic failure of therapy can result from subtherapeutic drug levels, monitoring of indinavir levels may be important in clinical management. We have developed a simple, accurate, and precise high-performance liquid chromatographic (HPLC) assay for measurement of indinavir concentration in human plasma. In our method, indinavir was extracted from plasma with dichloromethane at pH 10.4, which resulted in quantitative recovery of indinavir and the internal standard (IS), methyl-indinavir (86% and 80%-97%, respectively). Chromatographic separation was accomplished using a Luna C18 (2) (Phenomenex) analytic column with a mobile phase composed of acetonitrile:phosphate buffer (25 mM) and 0.2% triethylamine pH 7.0 (34.5:65.5, v/v). Ion-paired reagent triethylamine was necessary to ensure an appropriate retention time for indinavir and differentiate it from other protease inhibitors that were coextracted. Quantification was performed at 210 nm. The standard curves were linear (r2>0.999) over the concentration range 25-5,000 ng/mL, when 1-mL aliquots of plasma were extracted. Inter- and intraday coefficients of variation were acceptable. The assay was used to determine trough and peak levels of in plasma from 12 subjects who received indinavir 1200 mg every 12 hours, 1000 mg every 12 hours, or 800 mg every 8 hours. The concentrations of indinavir found in this study (trough 26-768 ng/mL; peak at 1 hr 3,309-17,568 ng/mL) has a wider range than defined previously (trough 50-300 ng/mL; peak 6,000-12,000 ng/mL). This study illustrates three potential uses of indinavir monitoring: to assess individual dosing regimen, to assess patient compliance, and to monitor unusual indinavir levels caused by changed drug clearance.     

Immobility stress induces depression-like behavior in the forced swim test in mice: effect of magnesium and imipramine

Previously, we demonstrated antidepressant-like effect of magnesium (Mg) in the forced swim test (FST). Moreover, the joint administration of Mg and imipramine (IMI) at ineffective doses per se, resulted in a potent reduction in the immobility time in this test. In the present study, we examined the effect of immobility stress (IS), and Mg and/or IMI administration on FST behavior. IS induced enhancement of immobility time, which was reversed by Mg or IMI at doses ineffective in non-stressed mice (10 mg/kg and 15 mg/kg, respectively). The joint administration of Mg and IMI was effective in both IS and non-stressed animals in FST. IS did not significantly alter locomotor activity, while IMI or Mg + IMI treatment in IS mice reduced this activity. We also measured serum and brain Mg, IMI and its metabolite desipramine (DMI) concentration in mice subjected to FST and injected with Mg + IMI, both restrained and non-restrained. In the present study we demonstrated a significant increase (by 68%) in the brain IMI and a slight, non-significant reduction in DMI concentration in IS + Mg + IMI + FST vs. Mg + IMI + FST groups, which might indicate the reduction in brain IMI metabolism. The IS-induced reduction in brain IMI metabolism did not participate in the activity in FST, since no differences in such activity were noticed between IS + Mg + IMI + FST and Mg + IMI + FST groups. The present data suggest that IS-induced increase in immobility time in FST is more sensitive for detection antidepressant-like activity. However, further studies are needed to examine the effect of other antidepressants in such an experimental paradigm.     

Effect of breast cancer resistance protein (Bcrp/Abcg2) on the disposition of phytoestrogens

The effect of breast cancer resistance protein (Bcrp/Abcg2) on the disposition of the phytoestrogens daidzein, genistein, and coumestrol was investigated using Bcrp(-/-) mice. Expression of the genes for either mouse Bcrp or human BCRP in MDCK II cells induced apically directed transport of the three phytoestrogens, whereas their transcellular transport was identical in mock and LLC-PK1 cells expressing mouse Mdr1a. After oral administration, the plasma levels of daidzein and genistein were increased in Bcrp(-/-) mice, but only a minimal change was observed for coumestrol. At steady state, tissue-to-plasma concentration ratios of the three phytoestrogens in the brain and testis of wild-type mice were very small and similar to those of [(14)C]inulin, whereas those were significantly increased in the brain and testis of Bcrp(-/-) mice. The largest increases were observed with genistein (9.2- and 5.8-fold in the brain and testis, respectively). The distributions of genistein in the epididymis and fetus, but not the ovary, were also increased in Bcrp(-/-) mice. The Bcrp protein was localized in the luminal membrane of the endothelial cells in the testis and the body of the epididymis and in both the luminal and abluminal side of ducts in the head of the epididymis. These results suggest that Bcrp limits the oral availability and distribution into the brain and testis, epididymis, and fetus of phytoestrogens.     

Analytical method for determination of allylic isoprenols in rat tissues by liquid chromatography/tandem mass spectrometry following chemical derivatization with 3-nitrophtalic anhydride

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method following chemical derivatization with 3-nitrophtalic anhydride was developed for the simultaneous determination of farnesol and geranylgeraniol in rat liver and testis. One analogue compound of the analytes, n-pentadecanol, was used as an internal standard (IS) for both analytes in this method. Rat tissues were disintegrated with 8% KOH ethanol solution, and then farnesol, geranylgeraniol and IS were extracted with a mixture of n-hexane-ethanol (98.5:1.5, v/v) in twice. Farnesol, geranylgeraniol and IS were then converted to 3-nitrophtalic derivatives of each analyte, and extracted with n-hexane. A turbo ion spray interface was used as the ionization source of LC-MS/MS and the analysis was performed in the multiple reaction monitoring (MRM) mode. The calibration curve at the spiked concentrations of 0.15-15 microg/g for both analytes showed good linearity. The method was precise; the relative standard deviations of the method for rat liver were not more than 13.4 and 5.4% for farnesol and geranylgeraniol, respectively, and those for rat testis were not more than 8.4 and 8.6% for farnesol and geranylgeraniol, respectively. The accuracies of the method for both rat liver and testis were good, with the deviations between the nominal concentration and calculated concentration of farnesol and geranylgeraniol typically being within 12.3 and 10.2%, respectively. This method provided reliable concentration levels for farnesol and geranylgeraniol in rat liver and testis.     

Lipid spectrum in different tissues of MT81 toxin-treated mice

The effects of different intraperitoneal doses of MT81 (2.5 mg/kg, 5.0 mg/kg and 7.5 mg/kg, respectively) for a 2-week, 4-week and 6-week treatment on concentration of total lipid and its different fractions of liver, brain, kidney, testis and serum in mice were studied. The following were measured: total lipid, free and total cholesterol, total phospholipid and its fractions (lecithin, lysolecithin, phosphotidylethanolamine and lysophosphotidylethanolamine), triglyceride, free fatty acid; lipase activity was also measured in serum, liver, and testis. Ascorbic acid content of testis was also measured. This mycotoxin (MT81) caused biochemical disorders of the tissues. Total cholesterol, free cholesterol, total phospholipid and its fractions, triglycerides and total lipids were elevated significantly in liver, serum, kidney and testis of toxin-treated animals. Free fatty acid increased significantly at a later stage in serum and remained constant in other tissues of toxin-treated mice. All the lipid fractions except total phospholipid and its fractions remained constant in brain of treated animals; total phospholipid and its fractions decreased significantly in brain of toxin-treated mice. Lipase activity decreased significantly in serum, liver and testis of treated mice. Ascorbic acid content of testis of treated animals increased significantly. Such disorders of lipid concentrations in the aforesaid tissues might be associated with the CNS depressant action and structural and functional toxicity of other tissues induced by the MT81 toxin.     

Acetylcodeine, an impurity of illicitly manufactured heroin, elicits convulsions, antinociception, and locomotor stimulation in mice.

Acetylcodeine is one of the major impurities present in illicitly manufactured heroin (diacetylmorphine). Data on its pharmacology and toxicology are limited and its ability to alter the toxic effects of diacetylmorphine is not known. The first objective of the present study was to compare the acute pharmacological and toxicological effects of acetylcodeine to those of codeine and diacetylmorphine in mice by assessing nociception in the tail-flick test, locomotor stimulation, and convulsive behavior. The second goal of this study was to determine whether acetylcodeine would alter the convulsant effects of diacetylmorphine. The antinociceptive potencies of acetylcodeine and codeine were similar, as reflected by their ED50 (95% confidence limits) values of 35 (29-44) and 51 (40-65) micromol/kg, respectively. Acetylcodeine was somewhat less potent than codeine in stimulating locomotor behavior, with ED50 values of 28 (22-37) and 12 (6-24) micromol/kg, respectively. Diacetylmorphine was considerably more potent than the other two drugs, producing antinociception and locomotor stimulation at ED50 values of 2.4 (1.4-4.1) and 0.65 (0.36-1.2) micromol/kg, respectively. On the other hand, the convulsant effects of acetylcodeine (ED50=138 (121-157) micromol/kg) and diacetylmorphine (ED50=115 (81-163) micromol/kg) were similar in potency and both were more potent than codeine (ED50=231 (188-283) micromol/kg). Finally, a subthreshold dose of acetylcodeine (72 micromol/kg) decreased the convulsant ED50 dose of diacetylmorphine to 40 (32-49). These findings suggest that the convulsant effects of acetylcodeine are more potent than predicted by its effects on locomotor activity and antinociception. The observation that acetylcodeine potentiated the convulsant effects of diacetylmorphine suggests a mechanism for some of the heroin-related deaths reported in human addicts.     

Potential renal and hepatic toxicity of diphenyl diselenide,diphenyl ditelluride and Ebselen for rats and mice

The occupational importance of tellurium and selenium is growing rapidly, but the biochemistry of exposure is poorly understood. Here we report the potential toxic effects of diphenyl diselenide (PhSe)(2), diphenyl ditelluride (PhTe)(2) and Ebselen in rats and mice. The results suggest that (PhTe)(2) is more toxic in rats than mice. (PhSe)(2), (PhTe)(2) and Ebselen are more toxic by intraperitoneal (i.p.) than subcutaneous (s.c.) route. Calculated LD(50) for (PhTe)(2), i.p., was 0.65 micromol/kg in rats and 150 micromol/kg in mice, and LD(50), s.c., was 0.9 micromol/kg in rats and >500 micromol/kg in mice. Calculated LD(50) for Ebselen, i.p., was 400 micromol/kg in rats and 340 micromol/kg in mice and LD(50), s.c., was >500 micromol/kg in both mice and rats. (PhTe)(2) at small doses increased 2-fold serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in rats. LD(50) for all organochalcogens administrated in mice inhibited blood delta-ALA-D activity. The present study provides evidence for liver and renal toxicity of (PhTe)(2).     

The effects of gestational arsenic exposure and dietary selenium deficiency on selenium and selenoenzymes in maternal and fetal tissues in mice

Although toxicological and metabolic interactions of arsenic (As) and selenium (Se) have been suggested by epidemiolgical literatures, the past experimental studies mostly focused on acute, high-dose interaction, leaving the long-term, low-dose interaction unexplored. In the present study pregnant mice, fed either Se-deficient or adequate (0 or 5 micromol Se/kg diet, respectively) diet, were given oral gavage of sodium arsenite (0 or 58 micromol/kg per day; chosen as less than half of the fetotoxic dose in this protocol) from gestational day (GD) 7-16. The levels of As and Se as well as five selenoenzymes (glutathione peroxidase (GPx), thioredoxin reductase (TRxR), and type-I, -II and -III iodothyronine deiodinases (DI-I, -II and -III) were examined on GD17 in the tissues of dams and of fetus. The Se-deficient mice showed significantly enhanced accumulation of As compared to the Se-adequate mice in maternal liver (increased by 48%) and fetal brain (by 31%). Although no direct evidence of the enhanced toxicity in the Se-deficient group was obtained, the As exposure affected the levels of Se and selenoenzymes, an effect which was more discernible in Se-deficient group. Although most of theses changes were mild or moderate, the DI-II activity in Se-deficient fetal brain showed a drastic four-fold increase by As exposure, suggesting a possible disturbance of thyroid hormone environment in the fetus. These data suggested that apparently non-toxic, in utero dose of As, showed enhanced accumulation when combined with Se-deficiency and could affect the metabolism/kinetics of Se in fetal brain, which might result in developmental toxicity in mice.     

褪黑素对不同月龄小鼠免疫反应的影响及其机制

目的:研究褪黑素对不同月龄小鼠免疫反应的影响及其作用机制。方法:淋巴细胞增殖采用MTT法;IL-2活性检测 采用激活小鼠脾淋巴细胞增殖法;cAMP测定用竞争蛋白结合法;甲硫氨酸脑啡肽的测定采用放免法。结果:6月龄和11月龄BALB/c小鼠胸腺淋巴细胞增殖能力和IL-2的产生均降低,褪黑素(5mg/kg或30mg/kg,ig×7d)对上述指标有不同程度的改善作用,在体外,11月龄小鼠胸腺淋巴细胞增殖反应明显降低,而其产生的cAMP则明显升高,褪黑素(0.1nmol/L和1μmol/L)对此有反向调节作用,弗司可林(10μmol/L)(腺苷酸环化酶选择性激活剂)能够增强2月龄和11月龄BALB/c小鼠胸腺淋巴细胞内的cAMP水平,褪黑素可部分拮抗此作用,褪黑素的这一作用可被百日咳毒素(1mg/L)完全取消,同时发现褪黑素(1μmol/L和0.1nmol/L)能够明显提高2月龄和11月龄BALB/c小鼠胸腺淋巴细胞的甲硫氨酸脑啡肽含量,这一作用能被硝苯地平(1μmol/L)所阻断,提示褪黑素促进淋巴细胞甲硫氨酸脑啡肽释放可能由Ca~(2+)通道介导。结论:褪黑素对不同月龄小鼠具有免疫调节作用;G蛋白偶联的AC-cAMP信号转导通路和淋巴细胞甲硫氨酸脑啡肽的释放可能是褪黑素发挥免疫调节作用的重要机制之一。     

Brain allopregnanolone regulates the potency of the GABA(A) receptor agonist muscimol

Allopregnanolone (ALLO), a potent positive-allosteric modulator of the action of GABA at GABA(A) receptors, is synthesized in the brain from progesterone by the sequential action of two enzymes: 5alpha-reductase and 3alpha-hydroxysteroidoxidoreductase. The concentration of ALLO in various parts of the mouse brain varies substantially, from 15 pmol/g in the olfactory bulb, to approximately 6 pmol/g in the frontoparietal cortex, and 2.7 pmol/g in the cerebellum. The systemic administration of 48 micromol/kg of the Type I and Type II 5alpha-reductase inhibitor, (17beta)-17-[bis (1-methylethyl) amino carbonyl)] androsta-3, 5-diene-3-carboxylic acid (SKF 105,111), reduced brain ALLO content by 80-90% in 30 min; the rate constant (k) of ALLO decrease in each brain area can be utilized to establish the rate of ALLO biosynthesis, which is higher in the olfactory bulb (62 pmol/g/h) than in the frontoparietal cortex (24 pmol/g/h) or cerebellum (11 pmol/g/h). The duration of the righting reflex loss elicited by the potent GABA(A) receptor agonist muscimol was reduced in SKF 105,111-treated ALLO-depleted mice. SKF 105,111 treatment had no effect on muscimol metabolism or on brain levels of pregnenolone and progesterone; however, the brain levels of 5alpha-DHP, the precursor of ALLO, were also decreased. Administration of ALLO at a dose of 15 micromol/kg i.p. by itself did not alter the muscimol-induced loss of the righting reflex; but it completely blocked the effect of SKF 105,111. To elucidate the possible molecular mechanism by which a decrease of brain ALLO content can shorten the duration of the righting reflex loss elicited by muscimol, we patch-clamped neocortical pyramidal neurons of mice pretreated with SKF 105,111 or vehicle, and studied the efficiency of muscimol in eliciting Cl- currents. The current amplitude was significantly smaller in neurons from SKF 105,111-treated mice, especially at lower doses (0.1-1 microM) of muscimol, and the muscimol dose-response (0.1-10 microM) relationship displayed cooperativity (nH=1.4). These data suggest that ALLO synthesized in brain plays an important physiological permissive role in the modulation of GABA-gated Cl- channel function.     

N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline studies on the role of 5-HT1A and 5-HT2 receptors in mediating foot-shock-induced ultrasonic vocalisation in adult rats.

The role of 5-HT1A and 5-HT2 receptors in mediating foot-shock-induced ultrasonic vocalisation has been studied in rats. Furthermore, behavioural effects were correlated to receptor reserves in the brain by means of receptor inactivation with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The dose-dependent inhibition of ultrasonic vocalisation by the 5-HT precursor, L-5-hydroxy-L-tryptophan (110-450 micromol/kg), was abolished by pretreatment with the 5-HT1A/1B antagonist, (-)-penbutolol (27 micromol/kg), and the 5-HT2A/2C antagonist, ritanserin (10 micromol/kg). The inhibitory actions of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and the 5-HT2A/5-HT2C. agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) were reversed by the 5-HT1A antagonist, (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide (WAY-100635), and the 5-HT2A antagonist, (+/-)alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorphenyl)ethyl]-4-pipe ridine-methanol (MDL 100151), respectively. Pretreatment with EEDQ (24 h, subcutaneous [s.c.]) inhibited foot-shock-induced ultrasonic vocalisation (effective dose50=0.95 micromol/kg) and decreased [3H]-8-OH-DPAT and [3H]-ketanserin binding in the brain. Pretreatment with WAY-100635 (0.3-20 micromol/kg) 20 min prior to EEDQ administration (1.3 micromol/kg, s.c.) did not reverse the EEDQ-induced inhibition of ultrasonic vocalisation but protected the 5-HT1A receptors against EEDQ inactivation. Pretreatment with MDL 100151 (0.83-54 micromol/kg) 20 min prior to EEDQ administration both reversed the EEDQ-induced inhibition of ultrasonic vocalisation and protected the 5-HT2A receptors against EEDQ inactivation. These findings demonstrate that 5-HT1A and 5-HT2 receptors are involved in the regulation of ultrasonic vocalisation in rats. However, the function of 5-HT1A and 5-HT2 receptors in this model seems to differ as vocalisation was preserved after protection of 5-HT2 but not 5-HT1A receptors.