bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Early Carbon Tetrachloride Toxicity in Cultured Rat Hepatocytes
Authors: Johnston David E. , Kroening Christine
Published: March 2009

Abstract:CCl4causes liver necrosis in a dose‐dependent mannerin vivo. However, we found that primary rat hepatocytes in culture were killed after a 2 hr incubation with carbon tetrachloride gas at CCl4partial pressures above a threshold between 45 and 54 mmHg. Below this threshold concentration no increase in hepatocyte death was observed. We sought to explain the very abrupt CCl4concentration threshold for hepatocyte death. Two inhibitors of cytochrome P450 2E1, cimetidine and diallyl sulfide, inhibited lipid peroxidation as measured by production of isoprostanes, but did not reduce hepatocyte death from CCl4. At 37°, CCl4accelerated the mitochondrial permeability transitionin vitro, at a threshold CCl4concentration similar to that which caused hepatocyte death. Phospholipase A2inhibitors, mepacrine and 4‐bromophenacyl bromide, inhibited the increase in mitochondrial permeability, but did not inhibit hepatocyte death caused by CCl4. Rat liver microsomal lipids were used to make liposomes loaded with Ponceau Red (FW 760.6). No leakage of Ponceau red was found at CCl4concentrations greater than the threshold for cell death. However, CCl4caused acceleration of liposome fusion, over the CCl4concentration range spanning the threshold for hepatocyte death. Early hepatocyte death in cell culture is independent of metabolism of CCl4, and may be related to direct effects of CCl4on intracellular membranes.
Effects of Tamoxifen, Toremifene and Chloroquine on the Lysosomal Enzymes in Cultured Retinal Pigment Epithelial Cells
Authors: Toimela Tarja , Salminen Lotta , Tähti Hanna
Published: March 2009

Abstract: Retinal pigment epithelial cells carry out phagocytosis and digestion of material shed from the photoreceptor outer segments. In this process, the integrity of lysosomal enzymes is of major importance. In the present study the effects of tamoxifen, toremifene and chloroquine on the activity of two lysosomal enzymes (cathepsin D and N‐acetyl‐β‐D‐glucosaminidase) in the retinal pigment epithelial cells were studied. Retinal pigment epithelial cells from pig eyes were cultured for two weeks in Dulbecco's Modified Eagle Medium, after which the cells were exposed to 1–40 μM concentrations of tamoxifen citrate, toremifene citrate and chloroquine diphosphate. To eliminate possible medium‐borne oestro‐genic mechanisms, the test was repeated using phenol red‐free medium with charcoal‐stripped fetal calf serum. The exposure time was one week, after which the lysosomal enzymes cathepsin D and N‐acetyl‐β‐glucosaminidase were determined. Cellular injuries were assessed by quantifying the leakage of lactate dehydrogenase into the culture medium. Cathepsin D and N‐acetyl‐β‐D‐glucosaminidase showed different sensitivities to tamoxifen, toremifene and chloroquine. The main lysosomal protease cathepsin D was more sensitive than N‐acetyl‐β‐D‐glucosaminidase to the effects of tamoxifen and toremifene, possibly due to their antioestrogenic properties. The phenol red‐free medium with charcoal‐stripped serum seemed to make the drugs more effective than the reference medium. Chloroquine had only a minor effect on the lysosomal protease cathepsin D, but a clearer effect could be seen on N‐acetyl‐β‐glucosaminidase.
Pharmacokinetics and Antidiuretic Effect of Intravenous Administration of Desmopressin in Orally Overhydrated Male Volunteers
Authors: Callréus Torbjörn , Höglund Peter
Published: March 2009

Abstract:In order to study the antidiuretic activity of desmopressin in healthy human subjects, a study design has previously been used with subjects orally hydrated. The objective of the present study was to investigate the pharmacokinetics and the antidiuretic activity of desmopressin administered as an intravenous infusion to eight orally hydrated male volunteers. After initial ingestion of water corresponding to 15 ml · kg–1body weight, the overhydration was maintained by replacing the urinary fluid loss by drinking‐water. Desmopressin (4 μg) was administered intravenously over 10 min. 1.5 hr after the start of the hydration procedure. Blood was sampled and urine was collected at intervals throughout the study day (9.5 hr). The terminal half‐life of elimination (t1/2) of desmopressin was calculated to be 2.97 ± 0.24 (S.E.M.) hr while the clearance was 1.77 ± 0.10 ml · min.–1· kg–1and the volume of distribution at steady state was 373 ± 30 ml · kg–1. The infusion caused a marked and long‐lasting reduction of the urine flow rate. Four hr after the start of the infusion the mean urine osmolality was 909 ± 46 mOsm · kg–1.
Fluoroquinolone‐Induced Motor Changes in the Guinea‐Pig Isolated Ileum
Authors: Nucci Amalia Di , Candura Stefano M. , Tagliani Monica , D'Agostino Gianluigi , Spelta Valeria , Fiori Enrico , Ricotti Paola , Tonini Marcello
Published: March 2009

Abstract:The effects of norfloxacin and enoxacin were examined on spontaneous motor activity in the guinea‐pig isolated ileum. Micromolar concentrations of both compounds caused a biphasic response consisting of relaxation followed by transient contraction. Relaxation to norfloxacin, which was unaffected by phentolamine, propranolol and hyoscine (each at 1 μM), was partially sensitive to tetrodotoxin (1 μM). This indicates that the response is partly mediated by non‐adrenergic non‐cholinergic (NANC) inhibitory nerves, and partly related to a direct action on the smooth muscle. Apamin (0.1 μM) and suramin (300 μM) inhibited norfloxacin‐induced relaxations to an extent similar to that of tetrodotoxin. Conversely, NG‐nitro‐L‐arginine (300 μM) was ineffective. In the presence of theophylline (100 μM) and 3‐isobutyl‐1‐methylxanthine (10 μM), norfloxacin caused relaxation less effective than when added alone. Based on this observation, the NANC component of the relaxation apparently depends on ATP release, whereas the direct component might be due, at least in part, to phosphodiesterase inhibition. Norfloxacin‐induced contractions were neurogenic and cholinergic in nature. They were reduced by indomethacin or S‐ketoprofen (both at 0.01–1 μM) and suramin (300 μM), suggesting involvement of local prostaglandin production probably induced by ATP release. Previous findings revealed that norfloxacin acted as a non‐competitive antagonist at enteric GABAAreceptors. In this study the same property was shared by enoxacin against the contractile response to 3‐aminopropane sulphonic acid (3‐APS), a GABAAreceptor agonist. In conclusion, fluoroquinolones exert inhibitory and excitatory effects in the guinea‐pig ileum. These are mediated by ATP, prostaglandin and acetylcholine release that might underlie, at least in part, the alterations of gastrointestinal motility observed after fluoroquinolone administration. Furthermore, isolated intestinal preparations might be useful to predict the GABAA‐antagonist potential of this class of compounds.
A Theoretical Approach to the Ferguson Principle and its Use with Non‐Reactive and Reactive Airborne Chemicals
Authors: Alarie Yves , Nielsen Gunnar Damgård , Abraham Michael H.
Published: March 2009

Abstract:The Ferguson principle has been widely used in toxicology to separate or indicate possible mechanisms for acute toxic effects of chemicals. However, this principle has never been adequately tested because of the lack of a database containing a sufficient number of both types of chemicals, non‐reactive and reactive, that the Ferguson principle purports to separate. Such a database is now available. In this report a theoretical framework for the Ferguson principle is presented, regarding one of the acute toxicological effects of volatile airborne chemicals: sensory irritation. Previously obtained results on series of non‐reactive and reactive chemicals are then used to demonstrate that the Ferguson principle can be extended to reactive chemicals by adding chemical reactivity descriptors to the physicochemical descriptors required by the Ferguson principle. This approach can be successful, provided that specific chemical reactivity mechanisms can be identified for the reactive chemicals of concern. The findings suggest that it is possible to replace the empirical Ferguson principle by formal mechanistic equations which will provide a better foundation for the understanding of the mechanisms by which airborne sensory irritants exert their action.
Heterocyclic Derivatives ofall‐transRetinoic Acid:in vitroEffects on Fibroblast/Keratinocyte Growth and Differentiation, andin vivoEffects on Guinea‐Pig Skin
Authors: Parnigotto Pier Paolo , Conconi Maria Teresa , Bortoletto Chiara , Manfredini Stefano , Montesi Francesco , Schiavon Mariano , Cancellotti Francesco Maria
Published: March 2009

Abstract:We investigated the biological effects of fiveall‐transretinoic acid derivatives, bearing heterocyclic ring systems in the side chain. Growth assays performed on submerged human fibroblast and keratinocyte cultures revealed that (E)4‐[2‐(5‐terbuthyl‐thiophen‐2‐yl)propenyl]benzoic acid (compound 5) is the best compound among the studied derivatives for it exibits a weaker antiproliferative activity and induces, likeall‐transretinoic acid does, a significant increase in fibroblast and keratinocyte growth. The morphological and morphometrical analyses of submerged human fibroblast cultures and human epidermis reconstructedin vitroshowed that the compound 5 behaves similarly toall‐transretinoic acid: it induces a decrease in all the cell parameters of submerged fibroblast cultures, and modulates the differentiation of keratinocytes inin vitroreconstructed epidermis. Compound 5 induces thickening of epidermisin vivo, one of the most remarkable pharmacological effects of retinoids on skin, but compared toall‐transretinoic acid, it induces a weaker irritation on guinea‐pig skin in terms of both erythema and scaling. Compound 5 could then represent a promising candidate for the treatment of certain dermatological diseases.
Effect of 3,4,5‐Trimethoxybenzoic Acid 8‐Diethylamino‐octyl ester (TMB‐8) on Neuronal Calcium Homeostasis, Protein Synthesis, and Energy Metabolism
Authors: Doutheil Jens , Paschen Wulf
Published: March 2009

Abstract:It has been suggested recently that disturbances of endoplasmic reticulum calcium homeostasis plays a major role in ischaemic cell injury of the brain. Depletion of endoplasmic reticulum calcium stores induces suppression of the initiation process of protein synthesis, a prominent feature of ischaemic cell damage. The benzoic acid derivative 3,4,5‐trimethoxybenzoic acid 8‐diethylamino‐octyl ester (TMB‐8), an established inhibitor of calcium release from endoplasmic reticulum, would be an ideal tool for elucidating the role of endoplasmic reticulum dysfunction in this pathological process. The present investigation was performed to study the effects of TMB‐8 on neuronal metabolism (cytoplasmic calcium activity, ATP levels and protein synthesis) using hippocampal slices and primary neuronal cell cultures. In addition, we investigated whether the rise in cytoplasmic calcium activity and the suppression of protein synthesis induced by endoplasmic reticulum calcium pool depletion, is reversed by this agent. Exposure of neurones to TMB‐8 (100 μM) induced a small transient increase in cytoplasmic calcium activity ([Ca2+]i), whereas a second dose of TMB‐8 (200 μM) produced a marked and sustained rise in [Ca2+]i. The increase in [Ca2+]ievoked by blocking endoplasmic reticulum Ca2+‐ATPase was only transiently suppressed and then aggravated by TMB‐8. The dose‐dependent suppression of protein synthesis by TMB‐8, observed both in neuronal cultures and hippocampal slices, indicates that TMB‐8 has a pathological effect on neuronal metabolism. This inhibition was not reversed after washing‐off of the drug. TMB‐8 did not reverse the inhibition of protein synthesis evoked by caffeine, which depletes endoplasmic reticulum calcium stores by activating the ryanodine receptor. The results indicate that TMB‐8 is not a suitable investigative tool for blocking in neuronal cell cultures the depletion of endoplasmic reticulum calcium stores and the suppression of protein synthesis induced by endoplasmic reticulum calcium pool depletion.
Threshold Concentrations of Endothelin‐1: The Effects on Contractions Induced by 5‐Hydroxytryptamine in Isolated Rat Cerebral and Mesenteric Arteries *
Authors: Hempelmann Ralf G. , Pradel Rainer H. E. , Mehdorn H. Maximilian , Ziegler Albrecht
Published: March 2009

Abstract:This study compares the effects of threshold concentrations of endothelin‐1 in isolated rat basilar arteries with those in mesenteric arterial branches and investigates the mechanisms of inhibitory and potentiating endothelin‐1‐effects. In basilar arteries, endothelin‐1 reduces the contractions induced by 5‐hydroxytryptamine (5‐HT), by the thromboxane A2agonist U46619, and by vasopressin. The inhibitory effect of endothelin‐1 on the contraction induced by 5‐HT is abolished by deendothelialization, by the endothelin ETBreceptor antagonist RES 701–1, by indomethacin, or by glibenclamide. In mesenteric arteries, endothelin‐1 potentiates the contractile effects of 5‐HT, U46619, and vasopressin. The potentiation of the contractile effect induced by 5‐HT is only somewhat modified by deendothelialization, but abolished by the thromboxane A2receptor antagonists GR32191 and ridogrel. U46619 potentiates the 5‐HT‐effect in mesenteric arteries. Thus, though the contractile endothelin ETAreceptors were not blocked, threshold concentrations of endothelin‐1 inhibited contractile effects in the rat basilar artery via activation of endothelial ETBreceptors. Prostaglandins and ATP‐sensitive K+channels are involved in this inhibitory action. In contrast, endothelin‐1 potentiates contractile actions in mesenteric arteries via the release of endogeneous thromboxane A2from non‐endothelial cells. The study points out the completely different role of the endothelium in combined effects of endothelin‐1 between cerebral and mesenteric arteries.
Extensive Biliary Excretion of the Sulfasalazine Analogue, Susalimod, but Different Concentrations in the Bile Duct in Various Animal Species Correlating to Species‐Specific Hepatobiliary Toxicity
Authors: Påhlman Ingrid , Andersson Stig , Gunnarsson Kjell , Odell Marie‐Louise , Wilén Maria
Published: March 2009

Abstract: Studies on biliary concentrations of susalimod were conducted in rat, dog and monkey to clarify the interspecies differences observed in toxicology studies with respect to hepatobiliary toxicity after long‐term administration of the compound. Dose‐related bile duct hyperplasia appeared only in dogs at doses ≥75 mg/kg/day, while in rats and monkeys it did not appear at doses up to 1500 and 2000 mg/kg/day respectively. Biliary excretion was investigated after intraduodenal administration of susalimod in anaesthetised animals. In addition excretion routes were determined by collecting urine and faeces following a radiolabelled intravenous dose. Susalimod was extensively excreted via the bile in all animal species, ≥90%, mainly as non‐conjugated parent compound. However, the local concentrations in bile varied between the species. Highest concentrations were obtained in the dog. The bile/plasma concentration ratio was 3400 in the dog, 300 in the monkey and 50 in the rat. In the dog, bile duct concentrations of susalimod about 30,000 μmol/l was obtained at plasma concentrations approximately similar to those at which hepatobiliary toxicity occurred, while in rat and monkey the levels were ≤7000 μmol/l at plasma concentrations similar to those obtained at the highest doses in the toxicology studies. From these results supported by a previous biliary excretion study in conscious dogs with chronic bile fistula receiving repeated administration of susalimod (Påhlman et al. 1999), it is likely that the hepatotoxic findings in dog are induced by the high concentrations of susalimod in the bile duct.
Midazolam α‐Hydroxylation by Human Liver Microsomesin vitro: Inhibition by Calcium Channel Blockers, Itraconazole and Ketoconazole
Authors: Wang Jun‐Sheng , Wen Xia , Backman Janne T. , Taavitsainen Päivi , Neuvonen Pertti J. , Kivistö Kari T.
Published: March 2009

Abstract:The inhibitory effects of five calcium channel blockers (diltiazem, isradipine, mibefradil, nifedipine and verapamil) and three azole antifungal agents (itraconazole, hydroxyitraconazole and ketoconazole) on the α‐hydroxylation of midazolam, a probe drug for CYP3A4‐mediated interactions in humans, were studiedin vitrousing human liver microsomes. IC50and Kivalues were determined for each inhibitor. The kinetics of the formation of α‐hydroxymidazolam were best described by simple Michaelis‐Menten kinetics. The estimated values of Vmaxand Kmwere 696 pmol min.−1mg−1and 7.46 μmol l−1, respectively. All the compounds studied inhibited midazolam α‐hydroxylation activity in a concentration‐dependent manner, but there were marked differences in their relative inhibitory potency. Ketoconazole was the most potent inhibitor of midazolam α‐hydroxylation (IC500.12 μmol l−1), being 10 times more potent than itraconazole (IC501.2 μmol l−1). The inhibitory effect of hydroxyitraconazole (IC502.3 μmol l−1) was almost as large as that of itraconazole. Among the calcium channel blockers, mibefradil was the most potent inhibitor of the α‐hydroxylation of midazolam, with an IC50value (1.6 μmol l−1) similar to that of itraconazole. The other calcium channel blockers were much weaker inhibitors than mibefradil: verapamil exhibited a modest inhibitory effect with an IC50of 23 μmol l−1, while isradipine, nifedipine and diltiazem, with IC50values ranging from 57 to >100 μmol l−1, were weak inhibitors. This rank order of potency against the α‐hydroxylation of midazolam was verified by the Kivalues. With the exception of diltiazem, thesein vitroresults conform with the observed interaction potential of these agents with midazolam and many other CYP3A4 substratesin vivoin man.
Normalization of Hyperglycaemia by Oral Vanadyl Sulfate Does Not Reverse Diabetes‐Induced Protection against Cisplatin Nephrotoxicity in Streptozotocin‐Diabetic Rats
Authors: Sarangarajan Rangaprasad , Cacini William
Published: March 2009

Abstract: Streptozotocin‐ and galactose‐induced diabetic rats are protected against nephrotoxic effects of cisplatin. While the mechanism remains to be defined, protection is associated with a decrease in the accumulation of platinum in renal cortical tissues of streptozotocin‐diabetic versus non‐diabetic rats. A physiological abnormality common to streptozotocin and galactosemic models of diabetes is hyperglycaemia, suggesting that elevated sugars are involved in mediating protection of diabetic kidney against cisplatin nephrotoxicity. The current study focused on the effect of normalization of hyperglycaemia by vanadyl sulfate trihydrate on the initiation of protection and accumulation of platinum in kidneys of streptozotocin‐diabetic rats. Streptozotocin‐diabetic rats were treated with 0.75 mg/ml of vanadyl sulfate trihydrate in drinking water to normalize streptozotocin‐induced hyperglycaemia. Vanadyl sulfate treatment normalized plasma glucose and glycosylated haemoglobin levels in streptozotocin‐diabetic rats to values observed for non‐diabetic rats. Intraperitoneal administration of cisplatin (5 mg/kg body weight) increased blood urea nitrogen by a factor >2.5 over baseline in both untreated and vanadyl‐treated non‐diabetic groups. Cisplatin‐induced increases in blood urea nitrogen were 1.6 times baseline in both untreated and vanadyl‐treated streptozotocin‐diabetic rats. Renal platinum accumulation was significantly lower in streptozotocin‐diabetic versus non‐diabetic rats regardless of vanadyl sulfate treatment. Renal vanadium levels in all groups of diabetic rats were not significantly different from each other. These results indicate that normalization of plasma glucose levels with vanadyl sulfate in streptozotocin‐diabetic rats did not reverse protection of streptozotocin‐diabetic kidney against cisplatin nephrotoxicitv.
Cytochrome P450 Sex Differences in Minipigs and Conventional Pigs
Authors: Skaanild Mette T. , Friis Christian
Published: March 2009

Abstract:Minipigs have become a popular alternative to the traditional non‐rodent species although little information is available on their P450 system. The total P450, the enzyme activity and immunochemical levels of some of the most important drug metabolizing isoenzymes CYP1A2, CYP2A6, CYP2C19, CYP2D6, CYP2E1 and CYP3A4 were measured in liver microsomes from 8 minipigs and 12 conventional pigs of both sexes and castrate conventional pigs. The mRNA expression was analyzed for 3 isoenzymes: CYP1A2, CYP2A6 and CYP2E1. The total P450 activity was slightly higher in minipigs compared to conventional pigs but no sex differences were detected. CYP1A2 activity was 4 times higher in female than in male minipigs. The activity of the male minipigs possessed the same activity as were identical to the conventional females, males and castrates. The activity of CYP2E1 was 4 times higher in female than in male minipigs and 2 times higher in female than in male pigs. No activity of CYP2D6 or CYP2C19 could be detected. The CYP3A4 activity detected in minipigs was higher than the activity in conventional pigs. A slight sex difference was seen in both strains. Correlations between enzyme activity and immunochemical levels were found for CYP1A2, CYP2A6 and CYP3A4 but not for CYP2E1. The mRNA concentration of CYP1A2, CYP2A6 and CYP2E1 was determined because the activity of these enzymes showed marked sex differences. A Spearman ranking correlation analysis between mRNA expression and enzyme activity showed a weak correlation for CYP2A6, but not for CYP1A2 and CYP2E1. These results seem to indicate that CYP2A6 could be transcriptionally regulated, whereas CYP1A2 might be post‐transcriptionally regulated.
Modulation of Drug‐Metabolising Enzyme Expression by Condensation Products of Indole‐3‐ylcarbinol, an Inducer in Cruciferous Vegetables
Authors: Vang Ole , Frandsen Henrik , Hansen Kristian T. , Nielsen Jesper Bo , Andersen Ole
Published: March 2009

Abstract:Indole‐3‐ylcarbinol (13C) is formed during processing of cruciferous vegetables and is suggested to be one of the modulators of drug‐metabolising enzymes. Indole‐3‐ylcarbinol is a far less efficient inducer of hepatic enzymes after parenteral than after oral administration, due to formation of active metabolites in the gastrointestinal tract. As indole‐3‐ylcarbinol is unstable in weakly acidic aqueous solutions, non‐active condensation products may be formed from indole‐3‐ylcarbinol, that cannot be transformed to the active products when reaching the stomach. The purpose of the present study was to test the ability of the condensation products formed at a pH corresponding to that of fresh vegetable juice to modulate the metabolism of xenobiotics. Indole‐3‐ylcarbinol was incubatedin vitroat room temperature in the dark at pH 5.5 and samples taken at various times, for oral administration to rats and for chemical analysis. Indole‐3‐ylcarbinol was rapidly transformed into various oligomeric products. The 7‐ethoxyresorufin O‐deethylase activities (marker of cytochrome Cytochrome P450 1A enzymes, CYP1A) in liver, kidney and colon increased with the duration of thein vitrocondensation period whereas the formation of 6β‐, 15β‐ and and 2α‐hydroxytestosterone was not affected significantly, indicating no effect on CYP2C11 or CYP3A enzymes. The hepatic metabolism of the food mutagen 2‐amino‐1‐methyl‐6‐phenylimidazo[4, 5‐b]pyridine (PhIP), was increased by indole‐3‐ylcarbinol condensation products and the 4′‐OH‐PhIP/N‐OH‐PhIP ratio was decreased due to a significantly increased formation of the proximate genotoxic metabolite,N‐OH‐PhIP. The activities of DT‐diaphorase and glutathione S‐transferase were not changed significantly in the rat organs. These experiments clearly indicate that indole‐3‐ylcarbinol is not the definitive CYP1A inducer and that indole‐3‐ylcarbinol at near‐neutral pH, is transformed to compounds that are inducers by themselves or may be further converted into inducing compounds in the rat stomach. Also, the enzyme inducing potency of indole‐3‐ylcarbinol containing vegetable juice is apparently enhanced by incubationin vitrobefore the intake.
Rat Offspring Treated Prenatally with Capsaicin Do Not Show Some of the Irreversible Effects Induced by Neonatal Treatment with Neurotoxin
Authors: Perfumi Marina , Sparapassi Lorenzo
Published: March 2009

Abstract:The present study evaluates whether some of the irreversible effects induced by neonatally administered capsaicin are present in offspring prenatally treated with the neurotoxin as well, and investigated its foetal toxicity. Capsaicin was administered subcutaneously at doses of 50, 100 and 200 mg/kg in five injections every other day between gestational days 7–15, the period of major organogenesis, or in a single subcutaneous injection of 50 mg/kg only at day 15 of gestation. In one‐month old rats prenatally capsaicin‐treated the response to noxious stimulation (hot plate and wiping tests) and the urinary excretion in response to oral water load were evaluated. Parallel experiments were conducted in one‐month old rats treated with capsaicin (50 mg/kg) on the 2nd day of life. Prenatal capsaicin induced no evident treatment‐related signs of toxicity in dams and offspring, nor did it influence the body growth of the pups or induce cutaneous lesions. Unlike neonatal treatment, prenatal administration of neurotoxin did not raise the threshold to thermal and chemical pain, and did not modify diuresis induced by oral load. Since researchers have proposed the existence of more than one population of capsaicin‐sensitive afferent neurones which differ in their age‐dependent sensitivity to capsaicin, we hypothesized that failure of prenatal treatment might be due either to reduced foetal availability, not capable of selectively destroying capsaicin‐sensitive neurones, or to incomplete rearrangement and maturation of developing primary sensory neurons, in fact, the existence is well known of more than one population of capsaicin‐sensitive afferent neurons which differ in their age‐dependent sensitivity to capsaicin. Future studies are needed to elucidate the effects of capsaicin at cellular and molecular levels.
The Inhibitory Effect of Ambroxol on Respiratory Burst, Degranulation and Cytosolic Ca2+ Change in Degraded Immunoglobulin G‐Activated Neutrophils
Authors: Park No Hyuk , Han Eun Sook , Lee Chung Soo
Published: March 2009

Abstract: Superoxide and H2O2 production by neutrophils stimulated by 0.5 mg/ml degraded immunoglobulin G (IgG) and 1 μM N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP) was inhibited by ambroxol in a dose‐dependent fashion, and at the concentration of 100 μM, 43.3% to 64.3% of inhibitions were detected. The inhibitory effect of ambroxol on H2O2 production by neutrophils was greater than that on superoxide production. The production of nitrite by lipopolysaccharide‐activated murine peritoneal macrophages was significantly attenuated by ambroxol in a dose‐dependent fashion and NG‐monomethyl‐L‐arginine (NMMA). Ambroxol decreased the release of myeloperoxidase and lysozyme evoked by 0.5 mg/ml degraded immunoglobulin G and 1 μM fMLP in a dose‐dependent fashion, and at the concentration of 100 μM, 37.1% to 64.2% of inhibitions were observed. The stimulatory effect of phorbol 12‐myristate 13‐acetate (PMA) (0.1 μg/ml) on superoxide production and myeloperoxidase, which is inhibited by 100 nM staurosporine, was not affected by 100 μM ambroxol. Degraded immunoglobulin G (0.5 mg/ml) caused an immediate elevation of [Ca2+]i, in fura‐2 load neutrophils in 1.23 mM Ca2+‐containing medium. Preincubation of neutrophils with 10 μM to 100 μM ambroxol, 5 mM EGTA and 100 μM verapamil depressed the elevation of [Ca2+]i elicited by 0.5 mg/ml degraded immunoglobulin G.

In conclusion, the inhibitory action of ambroxol on stimulated neutrophil responses, including respiratory burst and lysosomal enzyme release, appears to be attributed to its depressant action on the activation process, including the change in intracellular Ca2+ level, in which the role of protein kinase C is uncertain.
Region‐Selective Effects of Long‐Term Lithium and Carbamazepine Administration on Cyclic AMP Levels in Rat Brain
Authors: Wiborg Ove , Krüger Tanja , Jakobsen Søren N.
Published: March 2009

Abstract:The effect of lithium and carbamazepine in the treatment of bipolar affective disorder is well established. Although a number of biochemical effects have been found, the exact molecular mechanisms underlying their therapeutic actions have not been elucidated nor are the target regions in the brain identified. Taken into account the important role of the cyclic AMP second messenger system in the regulation of neuronal exitability and the indications of its involvement in the patophysiology of bipolar affective disorder, we have focused on the drug effects on cyclic AMP levels. The objectives of this investigation were to measure the effects on basal cyclic AMP levels, and to locate target regions within the rat brain after long‐term administration of lithium and carbamazepine. Drug treatments were carried out for a period of 28 days. After either drug treatment the cyclic AMP level was increased 3‐4 times in frontal cortex but unchanged in hippocampus, hypothalamus, thalamus, amygdala and in cerebellum. In neostriatum the cyclic AMP level was decreased to about 30% after treatment with lithium. We suggest the common region‐selective effect, observed for both drugs in frontal cortex, to be essential for the therapeutic actions of lithium and carbamazepine.
Interactions of Buspirone with Itraconazole and Rifampicin: Effects on the Pharmacokinetics of the Active 1‐(2‐Pyrhnidinyl)‐piperazine Metabolite of Buspirone
Authors: Kivistö Kari T. , Lamberg Tommi S. , Neuvonen Pertti J.
Published: March 2009

Abstract:The effects of inhibition and induction of the metabolism of buspirone on the plasma concentrations of 1‐(2‐pyrimidinyl)‐piperazine (a piperazine metabolite), the principal active metabolite of buspirone, were investigated. Two separate randomized, placebo‐controlled cross‐over studies with two phases were carried out in healthy volunteers. In Study I, six subjects took itraconazole 200 mg daily or matched placebo orally for 4 days. On day 4, 10 mg buspirone was administered orally. In study II, six subjects took rifampicin 600 mg daily or matched placebo orally for 5 days. On day 6, 30 mg buspirone was administered orally. Buspirone and piperazine metabolite concentrations in plasma were determined by gas chromatography. Itraconazole decreased the mean AUC of the piperazine metabolite by 50% (P<0.05) and the Cmaxby 57% (P<0.05) compared with placebo, whereas the mean AUC and Cmaxof unchanged buspirone were increased 14.5‐fold (P<0.05) and 10.5‐fold (P<0.05), respectively, by itraconazole. Rifzampicin had no significant effect on the AUC of the piperazine metabolite, but it increased the mean Cmaxof the piperazine metabolite by 35% (P=0.08). The mean AUC and Cmaxof parent buspirone were reduced by 91% (P<0.05) and 85% (P<0.05), respectively, by rifampicin. The mean ratio of the AUC of the piperazine metabolite to that of buspirone was decreased 34‐fold (P<0.05) by itraconazole and increased 7.6‐fold (P<0.05) by rifampicin. In conclusion, itraconazole and rifampicin caused only relatively minor changes in the plasma concentrations of the active piperazine metabolite of buspirone, although they had drastic effects on the concentrations of parent buspirone.
Intestinal Adsorption of Levothyroxine by Antacids and Laxatives: Case Stories and in vitro Experiments
Authors: Mersebach Henriette , Rasmussen Åse Krogh , Kirkegaard Lisbeth , Feldt‐Rasmussen Ulla
Published: March 2009

Two patients with hypothyroidism treated for upper dyspepsia and constipation with aluminum hydroxide and magnesium oxide, respectively, presented a marked increase in the serum concentration of thyroid stimulating hormone and low serum thyroxine on a fixed dosage of levothyroxine. After discontinuation of antacids/laxatives, thyroid stimulating hormone was again reduced indicating interaction between levothyroxine and antacids/laxatives. In vitro studies revealed a dose‐related increased adsorption of levothyroxine by addition of a combination of aluminum hydroxide, magnesium hydroxide and magnesium carbonate, while no connection between levothyroxine and the addition of magnesium oxide, alone, was found. This finding has major clinical consequences since 1) many patients are treated with levothyroxine, 2) most patients do not tell physicians that they take antacids/laxatives, and 3) consumption of antacids/laxatives in patients with levothyroxine‐treated hypothyroidism may lead to serious undersubstitution with levothyroxine.
Cyclosporin A and Trifluoperazine, Two Resistance‐Modulating Agents, Increase Ivermectin Neurotoxicity in Mice
Authors: Marques‐Santos Luis F. , Bernardo Robson R. , de Paula Emilio F. , Rumjanek Vivian M.
Published: March 2009

The P‐glycoprotein expressed in the blood‐brain barrier has been associated with the restricted access of many compounds to the central nervous system. Mice lacking themdr laP‐glycoprotein gene show an accumulation of various drugs in brain tissues. P‐glycoprotein is also correlated with the phenomenon of multidrug resistance in tumour cells. To investigate the effects of drugs that modulate multidrug resistance in the selective permeability of the blood‐brain barrier, mice were treated with cyclosporin A or trifluoperazine plus ivermectin, a P‐glycoprotein substrate, that has a limited access to the central nervous system. When mice received an injection of cyclosporin A (50 mg/kg, intraperitoneally) or trifluoperazine (750 μg/kg, intraperitoneally) one hour prior to the administration of ivermectin (10–15 mg/kg, intraperitoneally) there was an increase in the acute toxicity of ivermectin. HPLC analysis of brain tissues indicated that the ivermectin brain concentration was 2.5 times higher when mice were previously treated with cyclosporin A (50 mg/kg). These results suggest that attention should be given to the side effects of drugs that interact with P‐glycoprotein and are commonly used clinically and also to the possibility of creating a pharmacological gap in the blood‐brain barrier that allows the access of chemotherapeutic drugs to brain tumours.
Inhibition of Lipid Peroxidation by Pindolol
Authors: Miura Toshiaki , Muraoka Sanae , Fujimoto Yukio
Published: March 2009

Among β‐blockers, including atenolol, metaproterenol, pindolol and propranolol, only pindolol strongly inhibited lipid peroxidation induced by xanthine oxidase‐hypoxanthine in the presence of adenosine‐5′‐phosphate‐Fe3+. In the reaction system, superoxide predominantly reduced iron because superoxide dismutase strongly prevented the iron reduction. However, pindolol had no effect on the superoxide‐dependent iron reduction. Adding superoxide dismutase immediately stopped the lipid peroxidation, indicating that superoxide is closely connected with forming the initiator of xanthine oxidase‐hypoxanthine‐induced lipid peroxidation. On the other hand, pindolol also inhibited lipid peroxidation, whereas it did not react with superoxide, indicating that it inhibited xanthine oxidase‐hypoxanthine‐induced lipid peroxidation by an independent mechanism of superoxide. Pindolol sharply scavenged 2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulfonate) radical cations, but the ability of pindolol to scavenge peroxyl radicals of 2, 2′‐azobis (2‐amidinopropane)‐dihydrochloride and 2, 2′‐diphenyl‐p‐picrylhydrazyl radicals was low. In addition, pindolol did not scavenge hydroxyl radicals at physiologically significant concentrations. These results suggest that the ability of pindolol to inhibit lipid peroxidation was due to scavenging carbon‐centered radicals rather than peroxyl radicals.
Effect of Erythromycin and Itraconazole on the Pharmacokinetics of Oral Lignocaine
Authors: Isnhanni Mika H. , Neuvonen Pertti J. , Olkkola Klaus T.
Published: March 2009

Lignocaine is metabolized by cytochrome P450 3A4 enzyme (CYP3A4), and has a moderate to high extraction ratio resulting in oral bioavailability of 30%. We have studied the possible effect of two inhibitors of CYP3A4, erythromycin and itraconazole, on the pharmacokinetics of oral lignocaine in nine volunteers using a cross‐over study design. The subjects were given erythromycin orally (500 mg three times a day), itraconazole (200 mg once a day) or placebo for four days. On day 4, each subject ingested a single dose of 1 mg/kg of oral lignocaine. Plasma samples were collected until 10 hr and concentrations of lignocaine and its major metabolite, monoethylglycinexylidide were measured by gas chromatography. Both erythromycin and itraconazole increased the area under the lignocaine plasma concentration‐time curve [AUC(0–∞)] and lignocaine peak concentrations by 40–70% (P<0.05). Compared to placebo and itraconazole, erythromycin increased monoethylglycinexylidide peak concentrations by approximately 40% (P<0.01) and AUC(0–∞) by 60% (P<0.01). The clinical implication of this study is that erythromycin and itraconazole may significantly increase the plasma concentrations and toxicity of oral lignocaine. The extent of the interaction of lignocaine with these CYP3A4 inhibitors was, however, less than that of, e.g. midazolam or buspirone, and it did not correlate with the CYP3A4 inhibiting potency of erythromycin and itraconazole.
Inhibition of Mast Cell‐Dependent Anaphylaxis by Succinic Acid
Authors: Kim Hyung‐Min , Jung Hwan‐Suck , Shin Hye‐Young , Jung Kyu‐Yong
Published: March 2009

Abstract:We have examined the effect of succinic acid on anaphylaxis. Succinic acid (100 mM) significantly inhibited systemic anaphylaxis induced by compound 48/80 in mice, and dose‐dependently inhibited local anaphylaxis activated by anti‐dinitrophenyl IgE. Further 10 and 100 mM significantly inhibited histamine release from rat peritoneal mast cells activated by compound 48/80 or anti‐dinitrophenyl IgE. In addition succinic acid (0.1 and 1 mM) had a significant inhibitory effect on anti‐dinitrophenyl IgE‐induced tumour necrosis factor‐α secretion from rat peritoneal mast cells. The level of cyclic AMP in rat peritoneal mast cells, when succinic acid (100 mM) was added, transiently and significantly increased about 4 times compared with that of basal cells. These results suggest a possible use of succinic acid in managing mast cell‐dependent anaphylaxis.
Reversibility of Cholecystokinin‐B/Gastrin Receptor Blockade: A Study of the Gastrin‐ECL Cell Axis in the Rat
Authors: Norlén Per , Lindström Erik , Ding Xi‐Qin , Kitano Masayuki , Hákanson Rolf
Published: March 2009

Abstract:Gastrin acts via cholecystokinin‐B/gastrin receptors to control histamine‐ and chromogranin A‐producing ECL cells, which constitute the quantitatively predominant endocrine cell population in the acid‐producing part of the rat stomach. Cholecystokinin‐B receptor blockade is known to suppress the activity of ECL cells and to prevent their ability to respond to gastrin stimulation. The present study examines the reversibility of long‐standing cholecystokinin‐B receptor blockade of ECL cells. YM022, a potent and selective cholecystokinin‐B receptor antagonist, was administered in a maximally effective dose by continuous subcutaneous infusion for 4 weeks (via osmotic minipumps). The resulting receptor blockade was manifested in elevated serum gastrin concentration (due to the ensuing acid inhibition), while the serum pancreastatin concentration, oxyntic mucosal histidine decarboxylase activity, histidine decarboxylase‐ and chromogranin A‐ mRNA levels and histamine and pancreastatin concentrations were lowered. After withdrawal of YM022, all these parameters returned to normal after varying lengths of time. The serum gastrin concentration and the oxyntic mucosal histidine decarboxylase activity returned to normal within a week after termination of treatment. The serum pancreastatin concentration and the mucosal histidine decarboxylase‐ and chromogranin A‐mRNA levels returned to normal within 2 weeks of drug withdrawal. The mucosal pancreastatin and histamine concentrations remained unchanged for about a week before gradually returning to control levels within the next two weeks. Hence, the various effects of cholecystokinin‐B receptor blockade of the ECL cells are fully reversible within 1‐3 weeks of drug withdrawal.
Ethanol Potentiates Lead‐Induced Inhibition of Rat Brain Antioxidant Defense Systems
Authors: Jindal Vandana , Gill Kiran Dip
Published: March 2009

Abstract: We investigated the effect of alcohol (3 g/kg body weight intragastrically) on lead‐induced (50 mg/kg body weight intragastrically) oxidative stress in adult rat brain. Ethanol was found to potentiate the accumulation of lead in the rat brain by 100%. Lead and ethanol in combination also enhanced lipid peroxidation, a deteriorative process of biomembranes, and markedly decreased the antioxidant capacity of neuronal cells in terms of reduced activities of antioxidant enzymes i.e., superoxide dismutase, catalase and glutathione peroxidase. Further, the activity of glutathione reductase was also significantly decreased in lead and ethanol co‐exposed animals as compared to only lead‐treated animals, which had altered glutathione status. The results of the present study show that ethanol makes the adult rat brain more susceptible to the neurotoxic effects of lead by accentuating the oxidative stress induced by lead.
An Electrophysiological Analysis of Rat Ventral Tegmental Dopamine Neuronal Activity During Acute Toluene Exposure
Authors: Riegel Arthur C. , French Edward D.
Published: March 2009

Abstract:Inhalant abuse is a common, potentially lethal, form of drug abuse. Although the putative psychotropic component of some popularly abused inhalants appears often to be the organic solvent toluene, its effects on midbrain neurones which comprise reward pathways have not been established. Therefore, the present study was designed to assess the response of ventral tegmental dopamine neurones during toluene inhalation. Electrophysiological determinations were made using extracellular single‐unit recordings in ketamine anaesthetized rats that were exposed to acute (1–15.3 min.) concentrations of toluene vapor (11,500 ppm) similar to those consumed by inhalant abusers. Toluene exposure through a tracheal breathing tube elicited two distinctly different patterns of response in dopamine neurons. One pattern consisted of an initial stimulation of neuronal firing (+221%±72%;<8.5 min.) followed by an attenuation of the firing rate with continued exposure (+58.7%±6.3%; >8.5 min.). The other pattern consisted of only an inhibition of firing regardless of the length of exposure. Furthermore, the changes in firing rates were paralleled by changes in number of action potentials contained in bursts. Blood samples taken at the time of the dopamine recordings revealed comparable toluene concentrations (4–79 μg/ml, n=24) regardless of the patterns of response. These results suggest that mesolimbic dopamine neurotransmission can be changed by an exposure paradigm comparable to that used by human abusers, and that these changes may be integral to the reinforcing effects underlying inhalant abuse.
The Effect of in vitro Exposure to White Spirit on [Ca2+i] in Synaptosomes from Rats Exposed Prenatally to White Spirit
Authors: Edelfors Sven , Hass Ulla , Ravn‐Jonsen Andree
Published: March 2009

Abstract: Female rats were exposed to white spirit (400 and 800 ppm for 6 hr/day) at day 7–20 during pregnancy. Thirtyfive days after birth all female offspring were sacrificed, the brains removed, and the synaptosomal fractions prepared for in vitro studies. The cytosolic calcium concentration was measured using the FURA‐2 technique. The results show that cytosolic calcium was increased in synaptosomes from rats exposed to white spirit prenatally compared to synaptosomes from unexposed rats. When synaptosomes were exposed to white spirit in vitro, the cytosolic calcium concentration changes were identical in all groups of rats. The membrane leakage measured as FURA‐2 leakage from the synaptosomes identical in all three groups of animals. The results suggest that prenatal exposure to white spirit induces long‐lasting and possibly irreversible changes in calcium homeostasis in the rat nervous system.
Regulation of Cytochrome P4501A Metabolism by Glutathione
Authors: Otto Diana M. E. , Sen Chandan K. , Casley William L. , Moon Thomas W.
Published: March 2009

Abstract:Gene expression of cytochrome P4501A (CYP1A) in the rainbow troutOncorhynchus mykissis dependent on aromatic hydrocarbon receptor signal transduction, and is markedly sensitive to tissue thiol status. Tissue glutathione (GSH) status was manipulated by exogenous GSH, L‐buthionine‐[S, R]‐sulfoximine (BSO), lipoate or 1, 3‐bis(2‐chloroe‐thyl)‐1‐nitrosourea (BCNU). Tissue GSH contents were significantly elevated in GSH‐ and lipoate‐supplemented trout. Hepatic, renal and plasma GSH levels were markedly arrested in BSO‐treated trout. Oxidized glutathione (oxidized GSH) levels were significantly elevated in the BCNU‐supplemented group. Both BCNU treatment and BSO‐induced GSH deficiency increased steady‐state levels of hepatic CYP1A mRNA. Additional exposure to 0.1 mg/kg 3, 3′, 4, 4′‐tetrachloro‐biphenyl marginally suppressed the tetrachlorobiphenyl‐dependent CYP1A induction in BSO‐treated livers compared with the respective thiol treatment groups. Tetrachlorobiphenyl exposures altered efficiencies of thiol treatments and increased oxidized GSH content in all but the BSO‐treated groups. However, exposure to 5 mg/kg tetrachlorobiphenyl altered effects of thiol treatments on CYP1A mRNA to a small extent, but catalytic activity of CYP1A was many times suppressed in BSO‐treated and lipoate‐supplemented fish. These results suggest that thiol status interferes with CYP1A metabolism in a two‐way mode of action and provide further evidence for a cross‐talk between cytochrome P4501A and glutathione.
Role of Diltiazem on Tacrolimus Pharmacokinetics in Tacrolimus‐Induced Nephrotoxic Rats
Authors: Tada Hitoshi , Yanagiwara Seiko , Ito Kunihiko , Suzuki Toshio
Published: March 2009

Abstract:The effects of diltiazem on tacrolimus pharmacokinetics during tacrolimus‐induced nephrotoxicity were studied. In normal rats, co‐administration of diltiazem significantly increased AUC0–∞of tacrolimus and reduced total body clearance, Cltot, after intravenous and oral administration. In tacrolimus‐induced nephrotoxicity, AUC0–∞of tacrolimus increased 40.7%, while the apparent volume of initial distribution space, Vd1, the apparent volume of steady‐state distribution space, Vdss, and Cltot decreased 27.4%, 19.5% and 27.4%, respectively, as compared with the control. Co‐administration of diltiazem lowered the AUC0–∞of tacrolimus 36.2% and increased Vdli.v.62.8% in Vdss 45.9% and Cltoti.v.59.0% in tacrolimus‐induced nephrotoxicity, resulting in partial improvement in renal function. These pharmacokinetic alterations due to diltiazem contrasted with those seen in normal rats. As a result, the pharmacokinetic parameters in tacrolimus‐induced nephrotoxicity with coadministration of diltiazem resembled those in control rats. Mean tacrolimus concentrations in kidney cortex and medulla in a tacrolimus nephrotoxic group given diltiazem were 33.1% and 44.7% lower than those in a nephrotoxic model due to tacrolimus alone. But the tissue/blood concentration ratio of tacrolimus did not change regardless of the presence of diltiazem. Our findings suggest that co‐administration of diltiazem has an advantageous effects on tacrolimus pharmacokinetics to protect against tacrolimus‐induced nephrotoxicity.