bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Trypan Blue on the Action of Acetylcholine, Histamine and Salbutamol in the Isolated Guinea‐Pig Ileum
Authors: Mahmoudian M. , Damankeshideh M.
Published: March 2009

Abstract:It has been reported that trypan blue, a diazo dye with polyamphipatic structure, can inhibit the coupling of receptors to G‐proteins. This inhibition of G‐protein coupling has been investigated in isolated guinea‐pig ileum. It was found that trypan blue could elicit a slight but dose‐dependent contractile response in isolated guinea‐pig ileum (4.5% of maximum contractile response induced by acetylcholine). While trypan blue potentiated the effect of histamine and shifted its dose‐response curve to the left, it did not affect the contractile effects of acetylcholine. Furthermore, the relaxation which has been induced by salbutamol, a β2agonist, was inhibited by trypan blue. It is concluded that trypan blue, as shown in biochemical studies, act selectively and can uncouple Gs‐protein from β2receptors. However, the effect of trypan blue on the whole tissue preparation depends on the type of G‐protein involved and post G‐protein processes which are stimulated after receptor activation. Trypan blue and similar agents could provide useful tools for further investigations of the mechanism of receptor‐G protein coupling in the whole tissue preparation.
GYKI‐46 903, a Non‐Competitive Antagonist for 5‐HT3 Receptors
Authors: Csillik‐Perczel Viola , Bakonyi Anna , Yemane Tilahun , Vitalis Beata , Horvath Edith , Solyom Sandor , Szekely Jozsef I. , Harsing Jr Laszlo G.
Published: March 2009

Abstract: The effects of GYKI‐46 903 ((+)endo‐4‐propionyloxy‐6‐(4‐fluorophenyl)‐1‐azabicyclo [3.3.1]non‐6‐ene HCI), on 5‐HT3 receptors have been studied and compared with ondansetron in peripheral organs in vitro and in vivo, and in a receptor binding assay in membranes prepared from rat cerebral cortex. GYKI‐46 903 was found to be a non‐competitive antagonist at 5‐HT3 receptors present in non‐stimulated longitudinal muscle strip of guinea‐pig ileum (pD2’against serotonin=5.54), and also in 5‐methoxytryptamine‐pretreated electrically stimulated ileal preparations (pD2’against serotonin=5.26). On the contrary, ondansetron was found to be a competitive antagonist for 5‐HT3 receptors; the pA2 value against serotonin was 7.40 in non‐stimulated ileum, and it was 7.08 in electrically stimulated ileal preparation pretreated with 5‐methoxytryptamine. In displacement studies, the pIC50 values of GYKI‐46 903 and ondansetron against [3H]granisetron binding to rat cerebral cortex membranes were 6.91 and 8.58 respectively. GYKI‐46 903, when administered by intravenous infusion, antagonized the decrease in heart rate evoked by serotonin (Bezold‐Jarisch reflex) in anaesthetized rats, and the maximal reversal was less than 50%. This was in striking contrast with ondansetron, which, after intravenous injection, completely antagonized the serotonin‐induced bradycardia with an ID50 value of 3.28 ug/kg. These data classify GYKI‐46 903 as a non‐competitive antagonist for 5‐HT3 receptors.
Reverse Cholesterol Transport in the Rat Following a Short‐Term Intravenous Infusion of Fat Emulsion
Authors: Wang Wen‐Qi , Wang Xiang‐Dong , Sun Zheng‐Wu , Hanson Patrick , Gustafson Anders
Published: March 2009

Abstract: The effect on cholesterol transport of an intravenous infusion of a fat emulsion (10%) Intralipid® or 10% Lipovenös®) in vivo was investigated in the rat. Intralipid® (1.85 ml/hr/kg body weight in rts for 3 hr) caused a reduction (P<0.05) in free cholesterol in the aorta (by 25%), in plasma high‐density lipoproteins (64%) and in erythrocytes (11%) with a concomitant enrichment of liver free cholesterol (16%), suggesting an enhanced reverse cholesterol transport in this species. Lipovenös® under the same conditions gave similar results. Our data support our previous in vivo study in man indicating that infusion of a fat emulsion is able even to remove cholesterol from the arterial wall and thereby possibly be considered as an antiatherosclerotic agent.
Effects of Eicosapentaenoic Acid and Docosahexaenoic Acid Diet Supplement on Tolerance to the Cardiotoxicity of Epirubicin and to Ischaemia Reperfusion in the Isolated Rat Heart
Authors: Schjøtt Jan , Brurok Heidi , Jynge Per , Bjerve Kristian S.
Published: March 2009

Abstract: We compared the effects of 2 weeks dietary supplement of docosahexaenoic acid, eicosapentaenoic acid or olive oil on myocardial tolerance to the cardiotoxicity of the anthracycline epirubicin and to ischaemia reperfusion. Isolated rat hearts from the dietary groups were perfused at a constant flow rate of 12.5 ml/min. The hearts were subjected to a 20 min. period of epirubicin infusion by a side arm of the perfusion system at a rate of 0.2 mg/min. or a 20 min. period of global ischaemia. After 10 min. of epirubicin infusion a significantly (P<0.05) higher aortic pressure (an index of coronary resistance during constant flow perfusion) was observed in the olive oil group; 130±22% (mean±S.D.) compared to hearts in the docosahexaenoic acid; 108±9% (mean±S.D.), and eicosapentaenoic acid; 105±7% (mean±S.D.), group. Hearts from docosahexaenoic acid‐fed rats showed a significantly increased left ventricular end‐diastolic pressure (an index of contracture); of 66±30 mmHg (mean±S.D.) after 15 min. of global ischaemia compared to eicosapetaenoic acid fed rats; 37±18 mmHg (mean±S.D.), and significantly higher release of lactate dehydrogenase during the following 30 min. period of reperfusion compared to olive oil‐fed rats. We conclude that eicosapentaenoic acid and docosahexaenoic acid could be useful during epirubicin infusion and that docosahexaenoic acid could be harmful during ischaemia reperfusion.
Functional Characterization of Endothelin Receptors in the Bovine Retractor Penis Muscle and Penile Artery
Authors: Parkkisenniemi U.‐M. , Klinge E.
Published: March 2009

Abstract:The effects of endothelin‐1 and sarafotoxin 6c on the bovine retractor penis muscle and the bovine penile artery were studied, and a functional characterization of endothelin receptors in these tissues was performed by using the ETA‐receptor antagonist BQ‐123 and the ETB‐receptor antagonist IRL 1038. The retractor penis muscle and the penile artery were about equipotently contracted by endothelin‐1 in a concentration‐dependent manner the EC50values being 3.5 X 10‐9M and 1.3 X 10‐9M, respectively. In both tissues BQ‐123 (10‐6M) inhibited maximal contraction induced by endothelin‐1 by about 50%. Sarafotoxin 6c substantially relaxed the retractor penis muscle, and to a lesser extent also the penile artery, whereas endothelin‐1 did not relax either tissue. The sarafotoxin 6c‐induced relaxation of the retractor penis muscle was totally inhibited by IRL 1038 (3 X 10‐6M) and the nitric oxide synthase inhibitor L‐NNA (10‐4M). In both tissues L‐NNA enhanced the contraction induced by endothelin‐1 and lowered the threshold concentration for it. The results show that in both tissues the contraction induced by endothelin‐1 was mediated primarily by ETA‐receptors. The retractor penis muscle is also equipped with ETB‐receptors, probably at least in part located on the inhibitory nerves, which mediate relaxation via activation of the L‐arginine nitric oxide synthase pathway.
Effects of Dexamethasone on Sleep
Authors: Moser Neal J. , Phillips Barbara A. , Guthrie Gordon , Barnett Gary
Published: March 2009

Abstract: The purpose of this study was to evaluate the effects of acute systemic corticosteroid administration on sleep structure in healthy individuals. We conducted a randomized, prospective, double‐blind, placebo‐controlled cross‐over study of the effects of dexamethasone, 3 mg every eight hours for 48 hr on the sleep architecture of six normal volunteers (mean age 28 years, five males and one female). The subjects were participants blood pressure. Each subject was studied with a full polysomnogram on two successive nights when receiving either placebo or dexamethasone. Only the second night was used for analysis. Placebo and dexamethasone periods were separated by at least two weeks. There were significant increases in the REM latency, percent time spent awake and percent time spent in slow wave sleep in subjects taking dexamethasone when compared to their sleep while taking placebo. There were also significant decreases in the percent time spent in REM and the number of REM periods while on dexamethasone. We conclude that pharmacologic doseas of dexamethasone alter sleep architecture in healthy humans.
Cadmium‐Metallothionein Nephrotoxicity is Increased in Genetically Diabetic as Compared with Normal Chinese Hamsters
Authors: Jin Taiyi , Frankel Barbara J.
Published: March 2009

Abstract: To investigate the extra susceptibility of diabetics to some nephrotoxic agents, adult normal and diabetic Chinese hamsters (6‐7 animals in each group) were injected subcutaneously with different doses of cadmium‐metallothionein (Cd‐MT) equivalent to 0.0, 0.1 or 0.25 mg Cd/kg body weight and the first 24 hr urinary outputs were collected. Several days prior to exposure to the Cd‐MT the diabetic hamsters were hyperglycaemic, and plasma insulin levels and body weights were elevated in some of the diabetics. The higher dose of Cd‐MT caused significant spillage of N‐acetyl‐β‐glucosaminidase (U‐NAG) activity and protein into the urine of both normal and diabetic animals. The higher dose of Cd‐MT was more toxic to the diabetic kidneys because U‐NAG levels were higher in the diabetics (2.5‐fold higher than normal). U‐Cd levels were proportional to the injected Cd‐MT dose. U‐Zn levels were not consistently affected by the injected Cd‐MT although it had contained small amounts of Zn. Therefore, genetic diabetes in the Chinese hamster appears to increase susceptibility to acute cadmium‐MT nephrotoxicity. The mechanisms underlying this need to be further investigated.
Effects of Ethanol and Acetate on Adenosine Production in Rat Hippocampal Slices
Authors: Fredholm Bertil B. , Wallman‐Johansson Agneta
Published: March 2009

Abstract:Since adenosine has been shown to mediate some actions of ethanol we have examined the effect of ethanol (20 and 80 mM) or its metabolite acetate (5 and 20 mM) on the formation and release of adenosine by rat hippocampal slices. The ATP pool of the slices was radioactively labelled by preincubation with [3H]‐adenine. The efflux of radioactivity under basal conditions and following ATP breakdown induced by combined hypoxia/hypoglycaemia was examined. Ethanol or acetate did not increase the total efflux of [3H]‐purines, but changed the composition to a larger proportion of [3H]‐adenosine. The release of endogenous adenosine was also increased. This type of effect exactly mirrors that previously reported for purine nucleoside transport inhibitors. The present results thus show that ethanol (20 mM) can increase adenosine release from a brain slice by a mechanism that probably involves transport inhibition.
Evaluation of the Specificity and Potency of a Series of Cholecystokinin‐B/Gastrin Receptor Antagonists in vivo
Authors: Ding Xi‐Qin , Håkanson Rolf
Published: March 2009

Abstract:The potency and specificity of five proposed cholecystokinin‐B receptor antagonists, YM022, RP73870, L‐740,093, L‐365,260 and LY288513, were studied in rats and mice. Gastrin activates rat stomach histidine decarboxylase via cholecystokinin‐B/gastrin receptors. To examine cholecystokinin‐B receptor‐mediated effects of the five drugs, they were infused intravenously to fasted rats and the histidine decarboxylase activity in the oxyntic mucosa was determined. While YM022, RP73870, L‐740,093 and L‐365,260 failed to activate histidine decarboxylase, they dose‐dependently antagonized the gastrin‐induced histidine decarboxylase activation. LY288513 had no effect in the doses tested. The maximal inhibitory effect of L‐365,260, L‐740,093, RP73870 and YM022 on histidine decarboxylase, activated by the intravenous infusion of an ED50dose of gastrin (0.4 nmoles/kg/hr), was seen at doses of 3, 0.3, 0.1 and 0.1 μmoles/kg/hr, respectively; the corresponding ID50values were 0.4, 0.02, 0.007 and 0.004 μmoles/kg/hr. In a follow‐up study, YM022 and RP73870 were found to produce a rightward shift of the gastrin dose‐response curve, which is consistent with competitive inhibition. The effect of the five drugs on a cholecystokinin‐A receptor‐mediated response was examined by studying gastric emptying in mice. Cholecystokinin‐8s, given by a subcutaneous bolus injection, dose‐dependently inhibits gastric emptying. The specific cholecystokinin‐A receptor antagonist devazepide (given intravenously as a bolus injection) antagonized the effect of cholecystokinin‐8s in a dose‐dependent manner, with an ID50value of 28 nmoles/kg. None of the drugs inhibited the gastric emptying or prevented the cholecystokinin‐8s‐induced effect at the doses tested. The results indicate that YM022, RP73870, L‐740,093 and L‐365,260 act as cholecystokinin‐B receptor antagonistsin vivo, being without measurable agonistic activity. Furthermore, they do not interact with cholecystokinin‐A receptors at the doses tested. Among the cholecystokinin‐B receptor antagonists studied YM022 and RP73870 are superior, the rank order of potency being YM022±RP73870>L‐740,093>L‐365,260.
Effect of Mercuric Chloride Intoxication and Dimercaprol Treatment on σ‐Aminolevulinate Dehydratase from Brain, Liver and Kidney of Adult Mice
Authors: Emanuelli T. , Rocha J. B. T. , Pereira M. E. , Porciuncula L. O. , Morsch V. M. , Martins A. F. , Souza D. O. G.
Published: March 2009

Abstract:Dimercaprol is a compound used in the treatment of mercury intoxication, however with low therapeutic efficacy. It is assumed that dimercaprol acts by reactivating target sulfhydryl‐containing proteins. In the present investigation we studied the inhibitory effect of mercuric chloride treatment (3 days with 2.3 or 4.6 mg/kg HgCl2, sc) in mice on cerebral, renal and hepatic σ‐aminolevulinate dehydratase (ALA‐D) activity, and a possible reversal of the effect of mercury by dimercaprol (0.25 mmol/kg, 24 hr after the last mercury injection). Mercuric chloride did not inhibit cerebral ALA‐D at the doses injected. Dimercaprol treatment did not restore the normal enzyme activity of the liver after the 25% inhibition caused by 4.6 mg/kg HgCl2. In the kidney, dimercaprol enhanced the inhibitory effect of 4.6 mg/kg mercuric chloride (from 35% after mercury treatment alone to 65% after mercury plus dimercaprol treatment). Mercury content increased in kidney after exposure to 2.3 or 4.6 mg/kg and the levels attained were higher than in any other organ. Mercury accumulated in liver only after exposure to 4.6 mg/kg HgCl2, and dimercaprol further increased mercury deposition. Dimercaprol treatment also increased the levels of mercury in brain of animals exposed to 4.6 mg/kg HgCl2. The enzymes from all sources presented similar sensitivity to the combined effect of HgCl2and dimercaprolin vitro.In the absence of preincubation, 0‐500 μM dimercaprol potentiated the inhibitory effect of HgCl2on ALA‐D activity. In the presence of preincubation, and 100 and 250 μM dimercaprol enhanced ALA‐D sensitivity to mercury, whereas 500 μM dimercaprol partially protected the enzyme from mercury inhibition. Dimercaprol (500 μM) inhibited renal and hepatic ALA‐D when preincubated with the enzymes. These data suggested that the dimercaprol‐Hg complex may have a more toxic effect on ALA‐D activity than Hg2+. Furthermore, the present data show that dimercaprol did not act by reactivating mercury‐inhibited sulfhydryl‐containing ALA‐D, and that indeed it may have an inhibitory effectper sedepending on the tissue.
The Characterization of Oxotremorine‐Induced Hypothermic Response in the Rat
Authors: Ryan Pauline M. , Kelly John P. , Chambers Philip L. , Leonard Brian E.
Published: March 2009

Abstract: Oxotremorine is a muscarinic receptor agonist that induces a variety of physiological and behavioural effects including hypothermia in mice. These effects are antagonized dose‐dependently by classical anticholinergic compounds such as atropine. Although the oxotremorine‐induced hypothermic response has been demonstrated in mice, few studies of the effects of this muscarinic agonist have been made in the rat. The following studies were made in male Sprague Dawley rats: 1. an investigation of the dose‐response relationship between oxotremorine and hypothermia; 2. an examination of the effect of housing on the oxotremorine‐induced hypothermic response, and 3. an investigation of the acute administration of various doses of atropine sulphate on the hypothermia caused by oxotremorine. The results indicate that the dose‐response relationship between oxotremorine and the antagonism of hypothermia is similar in rat as it is in mice. The results also showed that this effect did not occur in group‐housed animals.
Differential Effects of Morphine‐6‐glucuronide, an Active Metabolite of Morphine, and Morphine on Locomotor Activity in Mice: Involvement of the Opioid Receptor
Authors: Uchihashi Yoshitaka , Kuribara Hisashi , Morita Toshihiro , Kitani Yasuharu , Karasawa Fujio , Sato Tetsuo
Published: March 2009

Abstract:Subcutaneous administration of morphine (2.5 to 20 mg/kg) or an active metabolite of morphine, morphine‐6‐glucuronide (2.5 to 20 mg/kg), increased the locomotor activity of mice in a dose‐dependent manner. Fifteen mg/kg of morphine and 20 mg/kg of morphine‐6‐glucuronide were almost equipotent. Subcutaneous administration of the universal opioid antagonist, naloxone, but not the δ‐selective antagonist, naltrindole, significantly suppressed the hyperlocomotion induced by morphine (15 mg/kg). On the other hand the subcutaneous administration of relatively higher doses of naloxone or naltrindole significantly reduced the hyperlocomotion induced by morphine‐6‐glucuronide (20 mg/kg). These findings suggest that agonistic actions at the opioid receptors, especially at the δ‐ and μ‐receptors, contribute to the morphine‐6‐glucuronide‐induced hyperlocomotion.
Pharmacokinetic‐Pharmacodynamic Modelling of Zopiclone Effects on Human Central Nervous System
Authors: Luurila Harri , Olkkola Klaus T.
Published: March 2009

Abstract:The present data shows the pharmacokinetics and concentration‐effect relationship of a single 7.5 mg oral dose of zopiclone in ten healthy volunteers. Plasma concentrations and effects of zopiclone on central nervous system as quantified by changes in saccadic peak velocity and digit symbol substitution test were measured for 17 hr after ingestion of zopiclone. Pharmacokinetics was described with a linear one‐compartment open model. Maximum effects preceded peak plasma zopiclone concentrations causing a clockwise hysteresis, i.e. proteresis, in concentration versus effect loops. Therefore, pharmacodynamics was described both with a tolerance model and a model with distributional pseudo‐tolerance where the concentration in the blood sampling site is assumed to equilibrate slower with arterial blood than the site of action of zopiclone. Both models related the changes in pharmacodynamics linearly to changes in zopiclone concentrations. The median (range) values for clearance, volume of distribution and elimination half‐life were 21 (15‐53) L/hr, 132 (58‐161) L and 3.4 (1.7‐5.7) hr, respectively. Both pharmacodynamic models were able to describe the relationship between zopiclone concentrations and changes in psychomotor performance equally well. However, because the pharmacodynamics of zopiclone were studied in a non‐steady‐state situation, the mechanism for proteresis, i.e. true tolerance versus distributional pseudotolerance cannot be identified.
Binding of3H‐Metronidazole in Olfactory, Respiratory and Alimentary Epithelia in Rats
Authors: Larsson Pia , Cybulski Wojciech , Tjälve Hans
Published: March 2009

Abstract:Whole‐body autoradiography of3H‐metronidazole in rats showed retention of bound metabolites in the epithelia lining the olfactory part of the nose, the tongue, the gingiva, the palate, the pharynx, the oesophagus and the forestomach.In vitromicroautoradiography in O2‐ and N2‐atmosphere with some of these tissues indicated reductive formation of bound metabolites in specific cells of the epithelia. Studies with subcellular fractions of the nasal olfactory mucosa showed formation of DNA‐ and protein‐bound metronidazole metabolites. A lower bioactivating capacity was found in experiments with the liver. The bioactivation was dependent on N2‐atmosphere, and presence of the P450‐inhibitor metyrapone or GSH in the incubation media depressed the protein‐binding of metronidazole both in the nasal olfactory mucosa and the liver. These data indicate that the bioactivation is partly P450‐dependent and GSH may play an important role in scavaging the bioactivated drug. The epithelial cells with a capacity to bioactivate metronidazole may be potential targets for negative effects of the drug. Whole‐body autoradiography also showed a strong binding of radioactivity in the contents of caecum and colon. This can be considered to be due to reductive bioactivation of metronidazole by the intestinal microorganisms and reflects the principal site of action of the drug.
Toxicity of Bupivacaine and Ropivacaine in Relation to Free Plasma Concentrations in Pregnant Rats: A Comparative Study
Authors: Danielsson Bengt R. G. , Danielson M. Kiki , Böö Éva Lindström , Arvidsson Torbjörn , Halldin Magnus M.
Published: March 2009

Abstract: The relationship between free drug concentration and toxicity of bupivacaine and ropivacaine, a new local anaesthetic agent, was studied in a pregnant rat model. The compounds were given subcutaneously to rats in late pregnancy. Dose levels (bupivacaine 5.5 to 24 mg/kg and ropivacaine 5.3 to 26 mg/kg) were selected based upon the proposed human dosage and the known pharmacological activity of the compounds. Chewing, spasm, dyspnoea, drowsiness, salivation and convulsions were observed in a dose‐dependent manner in the animals given 14 to 24 mg/kg of bupivacaine, while only a few animals receiving 26 mg/kg of ropivacaine showed less severe symptoms. Deaths from clonic convulsions were occasionally seen in animals receiving 14 mg/kg or more of bupivacaine. No animals receiving ropivacaine died. No effects on litter size, offspring loss or weight of the offspring at birth were observed with one exception. After 24 mg/kg of bupivacaine an increased postnatal loss of the off springs were noticed, most likely due to impaired maternal care. Protein binding, at expected Cmax, were significantly lower for ropivacaine (around 49%) compared with bupivacaine (around 69%) at dose levels. The results suggest an increased safety margin before onset of toxic side effects after treatment with ropivacaine, compared to bupivacaine, in pregnant rase.
B Lymphocytes in Mercury‐Exposed Workers
Authors: Queiroz Mary L. S. , Dantas Denise C. M.
Published: March 2009

Abstract: We have investigated the number of B lymphocytes in mercury‐exposed workers. The study group consisted of 33 workers from a mercury‐producing plant, mean age 27 years and a mean exposure period 19 months. At the time of testing and for the three previous months, the exposed persons had urinary mercury levels below the currently accepted limit of 50 μg g creatinine. A significant reduction in the number of B lymphocytes was observed in the mercury‐exposed individuals. We found no correlation between B lymphocytes changes and urinary mercury concentrations, length of exposure or age of the workers.
Interaction of Chymotrypsin with Carbetocin ([1‐deamino‐1‐monocarba‐2‐O‐methyltyrosine]‐oxytocin)
Authors: Vilhardt Hans , Atke Anders , Barthova Jana , Ubik Karel , Barth Tomislav
Published: March 2009

Abstract:The results of the present study describe the course of reaction and the products following chymotrypsin treatment of the oxytocin analogue carbetocin ([1‐deamino‐1‐monocarba‐2‐O‐ methyltyrosine]‐oxytocin). The metabolites were analyzed and identified through TLC, HPLC and mass spectrometry. The main product emerging after treatment of carbetocin with chymotrypsin is 9‐desglycineamide carbetocin indicating preferential hydrolysis of the peptide bond between leucine at position 8 and carboxyterminal glycineamide. At the same time the stability of the bond between tyrosine at position 2 and isoleucine at position 3 appears significantly enhanced through the alkylation of the hydroxyl group of tyrosine.
Actions of Spermicidal and Virucidal Agents on Electrogenic Ion Transfer across Human Vaginal Epitheliumin vitro
Authors: Levin Roy J.
Published: March 2009

Abstract:Human ectocervical tissue was removed at operation over the menstrual cycle mounted as a sheetin vitroin an Ussing‐style chamber and incubated in bicarbonate saline. The net electrogenic ion transport was measured as the short‐circuit current (Isc in μamps/cm2) and was characterised as mainly (60‐86%) an amiloride‐sensitive electrogenic Na+transport (lumen to serosa). Serosal application of amiloride had no effect. Serosal application of ouabain, a selective Na+‐pump inhibitor, reduced the Isc to near zero but neither theophylline (10 mM) nor furosemide (1 mM) had any action. The data are compatible with a model ectocervical vaginal cell having an amiloride‐sensitive Na+entry mechanism at the lumenal membrane and a Na+‐pump at the basolateral membrane removing the ion from the cell. The effects of the putative virucides, chlorhexidine and benzalkonium chloride, were tested on the preparation. Mucosally added chlorhexidine (2 mg/ml) had no effect on the Isc or tissue resistance but benzalkonium chloride, at concentrations between 0.06‐1.2%, caused a rapid fall in the Isc. At the highest concentration this was only partly reversible even after two washes with fresh buffer. At the lowest concentration (0.03%) benzalkonium chloride sometimes caused an initial increase in the Isc which then fell to zero. In all the tissues even after the Isc was reduced to near zero, nigrosin left in contact with the tissue for 5 min. did not enter and stain the cells, indicating the detergent had a selective membrane action rather than causing a non‐specific increase in permeability. The preparation allows objective measurements to be made of the initial acute membrane actions of putative spermicides and virucides on human vaginal ectocervical epithelial cells and offers a new approach of assessing their pharmacological/toxicological actions.
Combined Oral Treatment with racemic and meso‐2,3‐Dimercaptosuccinic Acid for Removal of Mercury in Rats
Authors: Kostial Krista , Restek‐Samaržija Nada , Blanuša Maja , Piasek Martina , Jones Mark M. , Singh Pramod K.
Published: March 2009

Abstract: Racemic dimercaptosuccinic acid (DMSA) was found more efficient than the meso‐isoform in enhancing the removal of mercury in rats. However. racemic‐DMSA has recently been found more toxic. The efficiency of combined oral treatment with the two isoforms of DMSA for removal of mercury has now been evaluated. Female albino rats were treated orally for four days with meso‐ (M) and/or racemic‐ (R) DMSA (1 mmol/kg each), five days after a single intraperitoneal administration of 203Hg with 0.5 mg HgCl2/kg. The animals were divided into six groups according to the number of treatments with each isomer: control (untreated), 4M, 1R + 3M, 2R + 2M, 3R+1M, and 4R. Whole body, kidney, liver and brain mercury contents were measured nine days after 203Hg administration. In all treated groups retention in the whole body and kidneys was greatly reduced. The groups treated with racemic‐DMSA, regardless of the number of doses, showed a greater removal of mercury than the group treated with meso‐DMSA alone (4M). All treatments were less efficient in reducing liver retention, and the brain retention was not affected. It was concluded that even a single application of the more toxic racemic‐DMSA during a four‐day oral treatment regimen is sufficient to improve the removal by meso‐DMSA of mercury from rats.
Differential Effects of Increasing Doses of α‐Trinositol on Cerebral Blood Flow Autoregulation
Authors: Vraamark Tina , Waldemar Gunhild , Edvinsson Lars , Paulson Olaf B.
Published: March 2009

Abstract: The effect of neuropeptide Y inhibition with α‐trinositol on the cerebral blood flow autoregulation was studied in Wistar Kyoto rats. α‐Trinositol was tested in two doses: one dose (5 mg kg‐1 hr‐1) selectively affecting neuropeptide Y and one higher dose (50 mg kg‐1 hr‐1) affecting both neuropeptide Y and the adrenergic response. The cerebral blood flow was measured with the intracarotid 133xenon injection method in halothane nitrous oxide‐anaesthetized animals. Blood pressure was raised by norepinephrine infusion and lowered by controlled haemorrhage in separate groups of rats. In addition we examined the effect of α‐trinositol on neuropeptide Y‐induced contraction of cerebral vessels in vitro. The in vitro study demonstrated inhibition of neuropeptide Y‐induced contraction with a α‐trinositol dose selective of neuropeptide Y. The in vivo study demonstrated that cerebral blood flow autoregulation was preserved after both doses of α‐trinositol. α‐Trinositol in the low neuropeptide Y‐selective dose (5 mg kg‐1 hr‐1) did not affect the blood pressure limits of cerebral blood flow autoregulation, but the higher dose (50 mg kg‐1 hr‐1) of α‐trinositol shifted the upper blood pressure limit of cerebral blood flow autoregulation towards lower blood pressures, an effect probably due to inhibition of both the adrenergic and neuropeptide Y systems.
Propofol‐Induced Ataxia and Hypnosis in Rat Lines Selected for Differential Alcohol Sensitivity
Authors: Yildirim Y. , Niemi L. , Wong G. , Korpi E. R. , Rosenberg P. H.
Published: March 2009

Abstract:An alcohol‐sensitive rat line, selectively bred for high sensitivity to ethanol‐induced motor impairment, also exhibits greater sensitivity to γ‐aminobutyric acid type A (GABAA) receptor agonists, such as benzodiazepines and barbiturates, than an alcohol‐insensitive rat line. We have investigated whether this difference was also maintained for the most recent intravenous anaesthetic, propofol. Propofol (100 mg/kg, intraperitoneally) induced similar sleep times and produced identical plasma propofol concentrations in alcohol‐sensitive and alcohol‐insensitive rat lines. At lower doses (50 and 75, but not 25 mg/kg), propofol produced a greater motor impairment in a tilting plane test in alcohol‐sensitive than alcohol‐insensitive rats shortly after the injection. Binding of a convulsant, [35S]t‐butylbicyclophosphorothionate, to cerebellar and cerebrocortical GABAAreceptors in the presence of 2 μM GABA was similarly affected by low micromolar propofol concentrations in both rat lines, while in the absence of GABA, propofol was slightly less potent in the alcohol‐sensitive than alcohol‐insensitive line. These data indicate that alcohol‐sensitive rats show transiently enhanced sensitivity to an ataxic, but not to a hypnotic dose of propofol, which cannot be explained by sensitivity differences to propofol in GABAAreceptors determined in a binding assay using brain membrane homogenates.
Effects of Tolbutamide on ATP‐Sensitive K+Channels from Human Right Atrial Cardiac Myocytes
Authors: Zünkler Bernd J. , Henning Berthold , Ott Tilmann , Hildebrandt Alfred G. , Fleck Eckart
Published: March 2009

Abstract:In order to gain further insight into possible deleterious effects on ischaemia‐induced myocardial damage induced by sulfonylureas when administered to humans, the effects of tolbutamide on ATP‐sensitive K+(KATP) channels from human right atrial myocytes were studied. Single myocytes were enzymatically isolated from human right atrium. The cell‐attached and inside‐out configuration of the patch‐clamp technique were employed at room temperature (both the pipette and the bath solution contained high [K+]). KATPchannels in inside‐out patches showed slight inward rectification, had a slope conductance of 75.1±2.4 pS (mean±S.E.M.; n = 5) at negative membrane potentials and these channels were blocked by ATP (half‐maximal block (EC50) at 39 μM; Hill coefficient= 1.65). In cell‐attached recordings, cromakalim (300 μM) opened KATPchannels (with a slope conductance of 73.3±1.8 pS (n=16) at negative membrane potentials) in previously silent patches. Cromakalim‐induced openings of KATPchannels were not markedly affected by 100 or 300 μM tolbutamide but were blocked by tolbutamide at millimolar concentrations (1‐3 mM). The concentration‐response relationship for tolbutamide‐induced block of KATPchannels in the presence of 300 μM cromakalim in cell‐attached patches was calculated to values for the EC50of 1.325 mM and for the Hill coefficient of 1.0, respectively. 1 mM tolbutamide‐induced block of cromakalim‐inducedKATP channel openings was not different at room temperature when compared to 37°. It is concluded that KATPchannels from human right atrial myocytes have a low sensitivity towards tolbutamide‐induced block.
Dopamine and Iron Induce Apoptosis in PC12 Cells
Authors: Velez‐Pardo Carlos , Jimenez Del Rio Marlene , Verschueren Hendrik , Ebinger Guy , Vauquelin Georges
Published: March 2009

Abstract:Recent studies have shown that Fe2+increases the oxidation of monoamines such as serotonin, dopamine and related toxins and that the formed oxidation products can undergo co‐valent binding to free sulphydryl groups of proteins such as actin and "serotonin binding proteins" which are present in soluble brain extracts. Here we have tested the ability of ferrous iron to induce [3H]dopamine association to cytoplasmic proteins and we have established that a similar oxidation mechanism evidencedin vitrostudies could be applied in cell culture. When PC12 cells were incubated with ferrous iron (ferrocene), the binding of [3H]dopamine to proteins was found to be two fold increased with respect to control. The iron is likely to accelerate the oxidation of dopamine to produce quinones which covalently bind to proteins and induce high‐molecular protein aggregates. We evidenced that dopamine/iron combination induced cell death in undifferentiated PC12 cells via an active cellular process evaluated in terms of morphological and biochemical changes indicative of apoptosis. We also demonstrated induction of lipid peroxidation when dopamine and ferrocene were present in high concentrations. Moreover, ascorbic acid diminished apoptosis but not the lipid peroxidation process. It might indicate that ferrocene and dopamine could produce oxidative stress of a different nature. These results show that the actions of dopamine and iron are essential in the induction of apoptosis and lipid peroxidation. However, there is no necessary causual link between lipid peroxidation and apoptosis. Our data also suggest that iron is capable of increasing the cytotoxicity of dopamine merely by increasing its rate of oxidation and without intervention of the monoamine oxidase B enzyme and, hence, both phenomenons may occur independently from each other in rat pheochromocytoma PC12. These observations may have relevance to the understanding of the mechanism by which dopaminergic neurones are destroyed in some neurodegenerative disorders.
NMDA Receptor‐Mediated Increase in Cyclic GMP in the Rat Cerebellum in vivo is Blocked by Alaproclate and GEA‐857
Authors: Hu Ping‐Sheng , Ross Svante B.
Published: March 2009

Abstract:The effects of alaproclate and GEA‐857 (2‐(4‐chlorophenyl)‐1,1‐dimethylethyl 2‐amino‐3‐methylbutanoate) on the production of cyclic GMP in the rat cerebellumin vivoinduced by stimulation of N‐methyl‐D‐aspartate (NMDA) receptors were studied. Alaproclateper seat a dose of 20 mg/kg subcutaneously. did not influence the basal cGMP level. The increase in cGMP induced by harmaline (20 mg/kg subcutaneously) was dose‐dependently antagonized by alaproclate (5‐40 mg/kg subcutaneously).S‐(‐)‐Alaproclate was 2‐5 times more potent than theR‐(+)‐enantiomer. GEA‐857 which in contrast to alaproclate is a very weak 5‐HT uptake inhibitor shared the ability of alaproclate to inhibit the effect of harmaline on cGMP accumulation with similar potency toS‐(‐)‐alaproclate. Alaproclate at 15 mg/kg subcutaneously blocked the increase in cGMP in cerebellum caused by NMDA itself at 200 mg/kg subcutaneously. In contrast to alaproclate, the K+channel antagonist, 4‐aminopyridine, 5 mg/kg subcutaneously, producedper sean increase in cGMP levels in the rat cerebellum by 300% which was antagonized by the NMDA receptor antagonists, dizocilpine, phencyclidine and (±)‐CCP, the nitric oxide synthase inhibitor, NG‐nitro‐L‐arginine methyl ester and by alaproclate. Alaproclate and GEA‐857 antagonized seizures induced by NMDA, 200 mg/kg subcutaneously at doses similar to those antagonizing the harmaline‐and NMDA‐induced elevation of cerebellar cGMP. Neither alaproclate nor GEA‐857 caused any behavioural effects typical for uncompetitive NMDA receptor antagonists except a slight increase in motor activity and sniffing. The effect of alaproclate on the NMDA receptor‐mediated increase in cGMP in rat cerebellumin vivomight be due to blockade of the cation channel of the NMDA receptor complex previously observed inin vitroexperiments and these compounds seems to belong to the group of low‐affinity uncompetitive NMDA receptor antagonists that might have clinical interest.
Effects of Ubiquinone and Mevalonic Acid on Hepatic Peroxisomal Enzymes Induced by Dehydroepiandrosterone
Authors: Khan Seher A. , Nyce Jonathan W
Published: March 2009

Abstract: The adrenal steroid, dehydroepiandrosterone (DHEA) has been identified as a peroxisome proliferator. We examined the effects of the cellular antioxidant ubiquinone and its precursor mevalonic acid on the induction of enzymes associated with DHEA‐mediated peroxisome proliferation in male F‐344 rats. Upon treatment with DHEA (300 mg/kg orally for 14 days), there was a significant increase in hepatic activities of peroxisomal β‐oxidation (3 fold), 3‐ketoacyl‐CoA thiolase (4 fold) and catalase (1.8 fold). Co‐administration of either mevalonic acid (100 mg/kg intraperitoneally) or ubiquinone (50 mg/kg orally) with DHEA significantly attenuated the DHEA‐mediated induction of these enzymes. However, neither ubiquinone nor mevalonic acid alone significantly altered peroxisomal enzyme activities in rat liver. These data suggest that exogenous administration of ubiquinone or mevalonic acid can modulate the induction of the enzymes involved in peroxisome proliferation.
Binding of Pinoline on the 5‐Hydroxytryptamine Transporter: Competitive Interaction with [3H] Citalopram
Authors: Pähkla Rein , Rägo Lembit , Callaway James J. , Airaksinen Mauno M.
Published: March 2009

Abstract:Pinoline (6‐methoxy‐1,2,3,4‐tetrahydro‐β‐carboline) is a naturally occurring compound in the mammalian body which inhibits 5‐hydroxytryptamine (5‐HT) uptake and exerts antidepressant‐like behavioural effects in rats. The present study investigates the effects of pinoline on [3H]citalopram binding to the 5‐HT transporter on rat brain. Our experiments revealed that pinoline inhibits [3H]citalopram binding with IC501255±167 nM and Ki572±76 nM; Hill coefficient for inhibition was close to 1. In saturation experiments, pinoline co‐incubated with [3H]citalopram, increased dose‐dependently the Kdvalue but had no effect on the Bmaxvalue of [3H]citalopram binding. Micromolar concentrations of pinoline did not have influence on the dissociation rate of specifically bound [3H]citalopram. Binding parameters of [3H]citalopram did not differ significantly in cerebral cortex and hippocampus of rats treated for 10 days with pinoline or vehicle. These results indicate that pinoline did not have any modulative influence on the activity of 5‐HT transporter and it interacts competitively with citalopram on the substrate recognition site of the 5‐HT transporter.
Effects of Perindopril and Hydrochlorothiazide on the Long‐Term Progression of Lithium‐Induced Chronic Renal Failure in Rats
Authors: Christensen Sten , Shalmi Michael , Hansen Axel Kornerup , Marcussen Niels
Published: March 2009

Abstract: Administration of lithium in the diet to new‐born rats induces chronic renal failure associated with hypertension, proteinuria and irreversible tubulo‐interstitial morphological changes. In the present study we induced chronic renal failure by administration of lithium for 16 weeks to new‐born rats, and examined the spontaneous course of this nephropathy and the effects of antihypertensive treatment with either perindopril (12 mg/kg diet) or hydrochlorothiazide (500–1000 mg/kg diet) during a 24 weeks follow up period without lithium. In the placebo group, progression to terminal uraemia occurred in all rats with severe renal failure (initial Purea >15 mM) (10 of 18). Rats with mild‐moderate renal failure (Purea 9–15 mM) showed no deterioration in renal function despite persistent systolic hypertension and irreversible structural renal changes. Perindopril normalized the blood pressure in all rats but did not prevent the progression to terminal uraemia (8 of 18). Hydrochlorothiazide partially controlled the hypertension and accellerated the progression of uraemia without increasing the mortality (7 of 17). Irrespective of treatments, the predominant quantitative structural changes (e.g. decreased volume of proximal tubular cells) showed significant correlations with the degree of renal dysfunction, but not with systolic blood pressure in the surviving rats. It is concluded that progression of lithium‐induced nephropathy to terminal uraemia occurs when the nephrotoxic insult results in a more than 50% reduction of the glomerular filtration rate, judged from Purea levels. The failure of effective antihypertensive treatment with an angiotensin‐converting enzyme inhibitor to modify the progression suggests that in this model, systemic or glomerular hypertension may not be an important pathophysiological factor. The structural and functional deterioration observed in Li‐uraemic rats during treatment with hydrochlorothiazide remains unexplained.
The Trophic Response of Rat Pancreas to Sulfated Cholecystokinin‐8 is Dose‐ and Time‐Dependent and Not Affected by Vagotomy or Atropine
Authors: Nylander Anna‐Greta , Chen Duan , Ding Xi‐Qin , Norlén Per , Håkanson Rolf
Published: March 2009

Abstract: Cholecystokinin (CCK) stimulates pancreatic enzyme secretion and growth. This study establishes the dose/plasma concentration ‐ and time ‐ response relationships for the trophic effect of CCK on the rat pancreas and evaluates the importance of vagal innervation and muscarinic receptors for the trophic effect. Rats received sulfated CCK‐8 (CCK‐8s) by continuous subcutaneous infusion. Different doses and different times of treatment were tested. The trophic effect was determined as wet weight and DNA content of the pancreas. The pancreatic weight and DNA content were found to depend not only on the plasma concentration of CCK‐8s but also on the duration of treatment. The EC50 value was 40 pmoles CCK‐8s per liter. This value should be compared with plasma CCK‐8s concentrations of 2–4 pmol/1 in intact fed rats. Maximum trophic effect was observed after 7–14 days of infusion. We conclude that although physiologically relevant concentrations of CCK‐8s may be important for the maintenance of the pancreas they do not induce growth. In another experiment atropinized, vagally denervated and intact rats were treated with a maximally effective dose of CCK for four days. The trophic effect of CCK‐8s was unaffected by vagotomy or atropinization.
Characterization of 1‐Hydroxypyrene as a Novel Marker Substrate of 3‐Methylcholanthrene‐Inducible Phenol UDP‐Glucuronosyltransferase(s)
Authors: Luukkanen Leena , Elovaara Eivor , Lautala Pia , Taskinen Jyrki , Vainio Harri
Published: March 2009

Abstract:Rats were treated with acetone, pyrazole, phenobarbital, 4,4′‐methylenebis‐(2‐chloroaniline) (MOCA), 3‐methylcholanthrene, creosote oil, or a mixture of polychlorinated biphenyls (Aroclor 1254) to study the inducibility and enzyme kinetics of UDP‐glucuronosyltransferases towards 1‐hydroxypyrene, which is a human metabolite and a urinary biomarker of exposure to pyrene. The rate of 1‐hydroxypyrene glucuronidation was analysed in rat liver microsomes by a fluorometric HPLC assay of the formed glucuronide. The apparent Kmand Vmaxvalues in untreated controls (Km= 0.27 mM; Vmax= 31 nmol/min./mg protein) did not differ markedly from those in rats treated with acetone, pyrazole or phenobarbital, whereas the significantly decreased Kmand increased Vmaxvalues of the rats treated with the carcinogenic chemicals, MOCA (0.11; 51), creosote (0.06; 137), 3‐methylcholanthrene (0.07; 141) or the Aroclor‐1254 polychlorinated biphenyl (PCB) mixture (0.08; 226), implicated major changes in the hepatic expression of UDP‐glucuronosyltransferases. 1‐Hydroxypyrene proved to be a high affinity substrate and a sensitive marker of the polycyclic aromatic hydrocarbon (PAH) metabolizing UDP‐glucuronosyltransferase(s). Catalytically, the most efficient isoforms were induced in creosote, 3‐methylcholanthrene and PCB‐treated rats showing Vmax/Kmratios which were 22–27 times greater than in untreated controls. Our findings suggest the existence of a 3‐methylcholanthrene type inducible and a functionally efficient low‐Km/high‐Vmaxform(s) of UDP‐glucuronosyltransferase(s) that detoxify 1‐hydroxypyrene and probably other polycyclic aromatic hydrocarbons as well.
Effects of Ethanol on Ethylmorphine Metabolism in Isolated Rat Hepatocytes: Characterization by Means of a Multicompartmental Model
Authors: Xu Bang Qian , Aasmundstad Tor A. , Lillekjendlie Bjern , Bjørneboe Anders , Christophersen Asbjørg S. , Mørland Jørg
Published: March 2009

Abstract:Hepatic cytochrome P‐450 enzymes mediate at least two important biotransformation pathways of codeine and ethylmorphine starting with either N‐demethylation or O‐dealkylation, producing polar metabolites which are then subsequently glucuronidated. The present study was designed to characterise the acute effects of ethanol on the metabolism of ethylmorphine and to compare it with the effects on codeine in suspensions of freshly isolated rat hepatocytes. Isolated rat hepatocytes from male Wistar rats were prepared by a collagenase perfusion method. Ethylmorphine, codeine and their metabolites were quantified by HPLC with UV detection. The total ethylmorphine elimination rate was reduced by 12% at 5 mM and 38% at 100 mM ethanol. The corresponding percentages for codeine were 16 and 43%. In the presence of ethanol the concentrations of several intermediate and end products of ethylmorphine and codeine changed markedly from the control situation. The experimental data were applied to a mathematical compartmental linear model to estimate the influence of ethanol on the separate reaction rates in the two main metabolic pathways. The ratios between reaction rate constants in the ethylmorphine experiments at 100 and 0 mM ethanol were 0.65 for ethylmorphine→norethyl‐morphine, 0.63 for norethylmorphine→normorphine, 0.56 for ethylmorphine→morphine, 0.49 for morphine→normor‐phine, 0.31 for normorphine→normorphine‐3‐glucuronide and 0.49 for morphine→morphine‐3‐glucuronide. Almost similar effects of ethanol on codeine metabolism were found. In additional experiments, norethylmorphine or norcodeine (50 μM) was incubated with 5 mM to 100 mM of ethanol and the metabolism of both norethylmorphine and norcodeine was found to be inhibited by ethanol in a concentration‐dependent manner. The glucuronidation of morphine and normorphine added in separate experiments was also inhibited by ethanol, from 22 to 36% for morphine‐3‐glucuronide and 30 to 60% for normorphine‐3‐glucuronide, respectively, in the presence of 5 mM to 100 mM of ethanol. It was concluded that all steps in the metabolism of ethylmorphine (and codeine) leading to the end products morphine‐3‐glucuronide and normorphine‐3‐glucuronide were inhibited by ethanol, and that the glucuronidation processes were the ones most affected by ethanol.