bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Buthionine Sulphoximine, Glutathione and Methimazole on the Renal Disposition of Cisplatin and on Cisplatin-induced Nephrotoxicity in Rats: Pharmacokinetic-Toxicodynamic Analysis
Authors: Hanada Kazuhiko , Mukasa Yuji , Nomizo Yuko , Ogata Hiroyasu
Published: October 2002

The aim of this study was to classify the protective mechanisms of DL-buthionine-(S,-R-)-sulphoximine, glutathione and methimazole on cisplatin-induced nephrotoxicity in rats. An Emax model was used to study the effect of these compounds on the pharmacokinetics of cisplatin, especially renal handling and intra-renal biotransformation.

Cisplatin (5 mg kg−1) was administered as an intravenous bolus to rats treated with either 0–9% NaCl (control), buthionine sulphoximine, glutathione or methimazole. The blood urea nitrogen level was monitored to estimate cisplatin-induced nephrotoxicity. To estimate renal handling of cisplatin, cisplatin was infused intravenously to rats treated with 0–9% NaCl, buthionine sulphoximine, glutathione or methimazole. The concentrations of unchanged cisplatin in plasma, urine and kidney were determined by a post-column derivatization HPLC method. The relationship between the pharmacokinetics and toxicodynamics of cisplatin was analysed using a sigmoid Emax model.

All compounds studied ameliorated significantly the nephrotoxicity of cisplatin. The renal accumulation of cisplatin was reduced significantly by pretreatment with buthionine sulphoximine but not by either glutathione or methimazole. Although glutathione treatment did not affect the renal accumulation of cisplatin, it significantly decreased the binding of cisplatin to the intrarenal organelle and the decreased binding was well correlated to the decrease of the blood urea nitrogen level.

In summary, pharmacokinetic-toxicodynamic analysis will be useful for classifying the protective mechanism of cisplatin-induced nephrotoxicity.
Determination of Tissue Spaces of the Isolated Hindlimb of the Rat Using Netilmicin as an Extracellular Space Indicator
Authors: Casquero-Dorado Ana Cristina , Sánchez-Navarro AMPARO
Published: October 2002

The kinetic behaviour of drugs in extracellular space is of interest as it influences the drug's access to, and permanence in, those areas of the body upon which drugs exert pharmacological or toxicological actions. A series of experiments was carried out to characterize the vascular, interstitial and cellular spaces of the isolated hindlimb of the rat. Certain specific experimental conditions were met: body weight was under 230 g to avoid fat tissue in the preparations; a perfusion flow rate of 3 mL min−1; and 3% of bovine albumin in the perfusate supplied at 25°C to the tissues.

The isolation of the hindlimb followed the method described by Ruderman with some modifications to restrict the perfusion to the right hindlimb. Tritiated water, netilmicin and methylene blue were injected separately and efferent fluid samples were collected for 15 min after solute injection. Analysis of the efferent curves was performed to calculate the statistical moments (AUC, area under concentration-time curve; MTT, mean transit time; VTT, variance of mean transit times) and solute distribution volumes, which were subsequently used to estimate the tissue spaces of the isolated hindlimb.

The results revealed that methyl blue and netilmicin can be respectively used as alternatives to radiolabeled indicators of the vascular and extracellular spaces of tissues included in the rat isolated hindlimb.
Protective Effects of Pseudoginsenoside-F11 on Scopolamine-induced Memory Impairment in Mice and Rats
Authors: Li Z , Guo Y Y , Wu C F , Li X , Wang J H
Published: October 2002

This study assessed the effects of pseudoginsenoside-F11, a component of Panax quinquefolium L., on scopolamine-impaired memory performance in mice and rats.

In the one-trial step-down and step-through passive avoidance tests, although pseudoginsenoside-F11 used alone did not affect passive avoidance behaviour in naive mice, the latency of avoidance shortened by intraperitoneal scopolamine (2 mg kg−1) was prolonged after intragastric administration of pseudoginsenoside-F11 (2 or 4 mg kg−1 for five days) in both test systems in mice. In the water-maze test, in mice, the time taken to locate the platform after administration of pseudoginsenoside-F11 was shorter than that after administration of scopolamine (1 mg kg−1 i.p.). In the two-way active avoidance response test, the latency of avoidance was significantly shorter for the pseudoginsenoside-F11-(1 · 2or 2 · 4 mg kg−1 i.g. for five days) and scopolamine-treated group than for the group of rats given scopolamine only (2 mg kg−1, i.p.). The percentage avoidance was also reduced after intraperitoneal injection of scopolamine, but was reversed by administration of pseudo-ginsenoside-F11.

These results suggest that pseudoginsenoside-F11 antagonized the memory dysfunction induced by scopolamine. However, the mechanism of the memory facilitative action of pseudoginsenoside-F11 merits further elucidation.
Effect of Saiboku-to, an Oriental Herbal Medicine, on Gastric Lesion Induced by Restraint Water-immersion Stress or by Ethanol Treatment
Authors: Yuzurihara Mitsutoshi , Ikarashi Yasushi , Kase Yoshio , Torimaru Yasutaka , Ishige Atsushi , Maruyama Yuji
Published: October 2002

The effect of saiboku-to on gastric lesions induced by restraint water-immersion stress and ethanol has been examined in rats.

Thirty minutes after oral administration of saiboku-to, the rats were placed in restraint cages and immersed in water at 23°C for 7 h, or orally administered 99.5% ethanol (1 mL) and placed in normal cages for 1 h. The stress for 7 h or the ethanol treatment for 1 h induced erosion in the glandular area of the stomach. Histology showed that the surface epithelial cells were desquamated and part of the lamina propria mucosae was injured. The evaluation of lesion index, the cumulative length of the gastric lesion, on the gross appearance of the stomach, revealed that saiboku-to dose-dependently inhibited both the water-immersion stress-induced gastric erosion and ethanol-induced gastric erosion. To determine whether the anti-erosion effect of saiboku-to was because of a mild irritant effect, saiboku-to or 20% ethanol, which is known as a typical mild irritant, were given orally. After 30 min a strong irritant, 99.5% ethanol, was given orally. Histological examination was performed 30 min after administration of saiboku-to or the mild irritant, and 1 h after administration of the strong irritant. The mild irritant induced a reduction in surface epithelial cells 30 min after administration. Furthermore, the mild irritant protected the stomach against mucosal erosion produced by the strong irritant. Saiboku-to protected the strong irritant-induced erosion without producing mild irritation as observed in stomach treated with 20% ethanol. Pretreatment with saiboku-to also inhibited the decrease in the levels of hexosamine, gastric mucus glycoprotein, induced by the strong irritant. In pylorus-ligated rats, saiboku-to dose-dependently inhibited gastric acid secretion, a gastric aggressive factor.

These results suggest that the anti-erosion effect of saiboku-to which is not a mild irritant, involves both inhibition of aggressive factors, such as gastric acid secretion, and augmentation of defensive factors, such as gastric mucus cells.
Preparation, Characterization and Biological Evaluation of Copper(II) and Zinc(II) Complexes with Cephalexin
Authors: Iqbal Mohammad S , Ahmad Abid R , Sabir Mohammad , Asad Syed M
Published: October 2002

Copper(II) and zinc(II) complexes of cephalexin have been prepared and characterized by microanalysis and by thermogravimetric, magnetic and spectroscopic analysis.

The complexes were found to be five-coordinate, monohydrate, and ML2 type. The electron paramagnetic resonance spectral lines revealed rhombic distortion from axial symmetry, with g∥ > g⊥ > ge, in the elongated-tetragonal copper(II) complex. The geometry of the zinc(II) complex seems to be square-pyramidal. On complexation with copper and zinc the antimicrobial activity of cephalexin improved significantly. The copper complex was found to be active against kaolin paw oedema whereas the parent drug was inactive.

These results suggest that the metallic elements should be seriously considered during drug design, and that complexes already reported should be subjected to clinical evaluation. Their use could provide an easy way of improving the activity and reducing the toxicity of drug substances.
Single- and Repeated-dose Local Toxicity in the Nasal Cavity of Rabbits after Intranasal Administration of Different Glycols for Formulations Containing Benzodiazepines
Authors: Hjortkjær Rolf K , Bechgaard Erik , Gizurarson Sveinbjörn , Suzdak Carol , Mcdonald P , Greenough R J
Published: October 2002

To furnish a systemic effect after intranasal administration, a formulation must contain the therapeutic dose in no more than 150 μL, the maximum volume that can be applied as a single administration in one nostril in man. The objectives of these studies were to examine the local toxicity of formulations containing benzodiazepines and to document the effects to support clinical trials in man.

After stability, pharmacological and pharmacokinetic studies of several benzodiazepine formulations, we studied nasal toxicity after single and repeated administration to rabbits of poly(ethylene glycol) 200, tetra(ethylene glycol), glycofurolum and mixtures of these vehicles both with and without benzodiazepines. Single-dose studies with examinations 5 or 10 min after application were undertaken with poly(ethylene glycol), tetra(ethylene glycol), glycofurolum and tetra(ethylene glycol)-glycofurolum in the ratio 95:5; the reactions were similar to that after physiological saline. A 14-day repeated-dose study was conducted with diazepam, lorazepam and flunitrazepam formulations in poly(ethylene glycol), and flunitrazepam in poly(ethylene glycol)-glycofurolum in the ratio 70:30; the two vehicles without any benzodiazepine were also examined. Microscopic study revealed mild changes only in the treated groups. A final four-week study was conducted with repeated administration of clonazepam formulated in tetra(ethylene glycol)-glycofurolum in the ratio 95:5; microscopy revealed mild changes after three 150-μL doses daily, but no abnormalities after one or three 100-μL doses daily.

It was concluded that these three solvents individually or as mixtures resulted in only mild local toxicity and might be acceptable as vehicles in nasal preparations of benzodiazepines and other non-irritating drugs for short-term use in man.
Pharmacokinetics of Ticlopidine in the Rabbit
Authors: Onyeji Cyprian O , Tessier Pamela R , Nightingale Charles H , Vallee Francois , Nicolau David P
Published: October 2002

There is no information about the pharmacokinetics of ticlopidine in rabbits. Such information is valuable in designing appropriate dosing regimens for experimental studies of the drug with ultimate applications in man. The disposition kinetics of ticlopidine at three dose levels were evaluated in three groups of six rabbits which received 10, 50 or 100 mg kg−1 drug once daily via the oral-gastric route. Blood samples were collected at predetermined times after the third dose. Plasma concentrations of the unchanged drug were determined by a validated liquid chromatography-mass spectrometry method with a limit of detection of 5 μg L−1.

There was a disproportionate increase in the mean maximum plasma concentration (Cmax) and the area under the plasma drug-concentration-time curve (AUC) for the 10 and 50 mg kg−1 doses. The apparent terminal half-life (t 1/2β), apparent volume of distribution (Vdβ/F), and total plasma clearance (CLp/F) of the drug were all dose-dependent. For example, t1/2β for the 10, 50 and 100 mg kg−1 doses were 1.04 ± 0.10, 4.24 ± 1.92 and 12.80 ± 6.35 h, respectively, whereas the Vdβ/F values for the corresponding doses were 214 ± 31, 475 ± 221 and 998 ± 420 L kg−1, respectively.

These results show that the 100-mg kg−1 dose produces plasma ticlopidine concentrations similar to those found in man after administration of 250 mg of the drug. It is suggested that 100 mg kg−1 might be the appropriate dose of ticlopidine for use in rabbit experimental studies with ultimate application to man.
Influence of Glycerol-induced Acute Renal Failure on the Pharmacokinetics of Cyclosporin in Rats
Authors: Shibata Nobuhito , Ohmae Takahiro , Hoshino Nobuo , Minouchi Tokuzo , Yamaji Akira
Published: October 2002

Although it is widely believed that renal dysfunction has no effect on the pharmacokinetics of cyclosporin, many clinical reports suggest that renal dysfunction after renal transplantation is closely related to the pharmacokinetics of cyclosporin. To clarify the relationship between renal dysfunction and the pharmacokinetics of cyclosporin, we examined the influence of acute renal failure (ARF) on its pharmacokinetics in glycerol-induced ARF rats.

The values of indicators of renal function (serum creatinine, blood urea nitrogen), but not those of indicators of hepatic function, were significantly increased in ARF rats that received glycerol compared with values for control rats. The area under the blood cyclosporin concentration-time curve after oral administration (AUCpo) were 4.976 ± 0.847 mg hL−1 for ARF rats and 9.684 ± 1.100 mg hL−1 for control rats; AUCpo in ARF was significantly reduced in a manner dependent on renal function. The oral clearance of cyclosporin in ARF and control rats was 1.172 ± 0.207 and 0.544 ± 0.062 Lh−1 kg−1, respectively, whereas total body clearance in ARF and control rats was 0.151 ± 0.008 and 0.183 ± 0.010 Lh−1 kg−1, respectively. The relative bioavailability of cyclosporin in ARF and control rats was 0.118 and 0.336, respectively. In an in-vitro study using everted sac and liver-slice methods, the apparent first-order rate constants for cyclosporin uptake (kuptake) and metabolism (kmetab) in gut tissues were reduced, whereas kuptake and kmetab in liver were increased. Gastric emptying, measured by use of paracetamol, was significantly reduced in ARF rats.

These results suggest that glycerol-induced ARF results in several changes in the pharmacokinetics of cyclosporin in rats. From these results, we conclude that reduction of the absorbed fraction of cyclosporin strongly contributes to the decrease in AUCpo in the presence of ARF.
Aldehyde Oxidase-catalysed Oxidation of Methotrexate in the Liver of Guinea-pig, Rabbit and Man
Authors: Jordan C Geraldine M , Rashidi Mohammed R , Laljee Hussain , Clarke Stephen E , Brown John E , Beedham Christine
Published: October 2002

Although 7-hydroxymethotrexate is a major metabolite of methotrexate during high-dose therapy, negligible methotrexate-oxidizing activity has been found in-vitro in the liver in man. The goals of this study were to determine the role of aldehyde oxidase in the metabolism of methotrexate to 7-hydroxymethotrexate in the liver and to study the effects of inhibitors and other substrates on the metabolism of methotrexate. Methotrexate, (±)-methotrexate and (-)-methotrexate were incubated with partially purified aldehyde oxidase from the liver of rabbit, guinea-pig and man and the products analysed by HPLC. Rabbit liver aldehyde oxidase was used for purposes of comparison.

In-vitro aldehyde oxidase from the liver of man catalyses the oxidation of methotrexate to 7-hydroxymethotrexate, but the turnover is low. However, formation of 7-hydroxy-methotrexate from all forms of methotrexate by the liver in guinea-pig and man was significantly inhibited in the presence of 100 μM menadione and chlorpromazine, potent inhibitors of aldehyde oxidase. Allopurinol (100 μM) had a negligible inhibitory effect on liver aldehyde oxidase from guinea-pig and man. Allopurinol is a xanthine oxidase inhibitor. The production of 7-hydroxymethotrexate was enhanced in the presence of allopurinol. Although aldehyde oxidase is also responsible for some of this conversion, it is also possible that the closely related xanthine oxidase is responsible for the formation of 7-hydroxymethotrexate.

By employing potent selective inhibitors of aldehyde oxidase, menadione and chlorpromazine, we have demonstrated for the first time that liver aldehyde oxidase from man is minimally involved in methotrexate oxidation.
Mucolytic and Antitussive Effects of Erdosteine
Authors: Hosoe Hisashi , Raise Toshihiko , Ohmori Kenji , Isohama Youichirou , Kai Hirofumi , Takahama Kazuo , Miyata Takeshi
Published: October 2002

To investigate the influence of erdosteine, a new homocysteine-derived expectorant, on airway clearance we studied the effects of the drug on the viscosity of mucin, on the mucociliary transport rate in quails, on airway secretion in rats and on the cough reflex in guinea-pigs.

The active metabolite of erdosteine, M1 (10 μM to 1 mM), significantly reduced the viscosity of porcine stomach mucin. Erdosteine by itself did not reduce viscosity. Erdosteine significantly promoted mucociliary transport in quails and increased airway secretion in rats. The effect was still apparent 24 h after administration. Erdosteine significantly suppressed citric acid-induced cough reflexes in guinea-pigs but did not suppress mechanical stimuli-induced cough reflexes. Erdosteine suppressed the reduction of the recovery volume of bronchoalveolar lavage fluid and albumin leakage into the fluid in citric acid-exposed guinea-pigs.

These results indicate that erdosteine removes sputum by reducing its viscosity, and by promoting mucociliary transport and sustained enhancement of airway secretion. It also suppressed the chemical stimulation-induced cough reflex and plasma leakage into the airway. These results suggest that erdosteine is an excellent expectorant with several modes of action.
Chronopharmacokinetics: Implications for Drug Treatment
Authors: Lemmer Björn
Published: October 2002

Nearly all functions of the human body are organized across the 24 hours of the day. This is also true for functions involved in the regulation of pharmacokinetics such as gastric absorption and emptying, gastro-intestinal perfusion, and liver and kidney functions. Several clinical studies, performed in a cross-over design, have provided evidence that the pharmacokinetics of mainly lipophilic drugs can be circadian phase-dependent. These studies show that after oral dosing, peak drug concentration (Cmax) is, in general, higher or time-to-peak (tmax) shorter after morning, compared with evening application. A few studies performed with both immediate-release and sustained-release preparations (iso-sorbide-5-mononitrate, nifedipine) gave evidence that only the immediate-release formulation displayed circadian time-dependent pharmacokinetics, but not the sustained-release form. Most importantly, pharmacodynamic studies performed in parallel revealed that the effects, as well as the dose-response relationship, can be circadian phase-dependent, an observation which has an impact on pharmacokinetic/pharmacodynamic modelling. Moreover, this can be of relevance because the onset of certain diseases (e.g., bronchial asthma, coronary infarction, angina pectoris, rheumatic complaints) is not randomly distributed across the 24-h scale. In conclusion, there is now convincing evidence that the time-of-day has to be taken into account both in clinical pharmacokinetic and pharmacodynamic studies.
Cancer Chronotherapy
Authors: Lévi Francis
Published: October 2002

The cytotoxicity of more than thirty anticancer drugs varies by more than 50% as a function of dosing time along the 24-h time-scale in laboratory animals. Mechanisms involve circadian changes in cellular metabolism and proliferation processes, as well as drug pharmacokinetics. Moreover, the administration of chemotherapy at the least toxic time usually achieves best antitumour efficacy in experimental tumour models. Here we review experiences in utilising these phenomena in the optimization of cancer chemotherapy in the clinic.

Chronotherapy has been administered to 1500 patients with metastatic colorectal cancer using 5-fluorouracil and leucovorin with or without oxaliplatin. Sinusoidal chronomodulated delivery of 2- or 3-drug chemotherapy was performed in the patient's home or during usual activities, with a computer-programmed multi-reservoir pump. Courses lasted 4–5 days and were repeated every 14–21 days. Three-drug chronotherapy proved largely superior to flat infusion with respect to both tolerability and antitumour efficacy. The better tolerability of chronotherapy further allowed an increment of both 5-fluorouracil and oxaliplatin doses, which in turn further improved objective tumour response rate to 66%. This enabled surgical removal of previously inoperable metastases and the achievement of > 20% survival at three years.

Second generation programmable-in-time pumps have simplified chronotherapy administration and decreased its costs. A broad use of fully ambulatory chronotherapy requires thorough definitions of drug stability, and compatibility with pump reservoirs and other medications.
Breaking out of the Ivory Tower: from Academia to Clinic
Authors: Woolfson A D
Published: October 2002

This paper considers the relationship between academic research and industry in terms of the commercial exploitation of product or process driven programmes originating in academic institutions. The commercial exploitation of pharmaceutical research is the only practical means of achieving the desired end-point of all research programmes in the pharmaceutical sciences—achieving patient benefits. The requirements for generating intellectual property rights (IPR), types of IPR likely to be encountered, time scales, costs, potential partnerships and commercial routes for exploitation are discussed. The ability to link up with industry to exploit new pharmaceutical products or processes is exemplified through two models. Model 1 involves out-licensing of IPR generated wholly within an academic setting and is illustrated by reference to the development of Ametop Gel, a novel percutaneous anaesthetic preparation. Model 2 involves a partnership with industry in a risk-sharing format, with both partners contributing expertise to the project. This latter model is illustrated by reference to a new controlled and sustained release intravaginal ring delivery system for oestrogen replacement therapy.
The Influence of Plasma Binding on Absorption/Exsorption in the Caco-2 Model of Human Intestinal Absorption
Authors: Walgren Richard A , Walle Thomas
Published: October 2002

The Caco-2 cell monolayer has become an increasingly useful in-vitro model of human intestinal absorption. In this study we have determined the effect of plasma on the basolateral side on the absorption as well as exsorption of several drugs that are highly bound to plasma proteins. The drugs used included propranolol and quercetin, which both use the transcellular route of absorption, and taxol and oestradiol 17 β-D-glucuronide, which are thought to undergo efflux by P-glycoprotein and the multidrug resistance protein MRP, respectively. All experiments were carried out under sink conditions to mimic normal absorption. It was necessary to use heparin anticoagulation for generation of the plasma, as EDTA was found to make the monolayers very leaky.

The apparent permeability (Papp) values for absorption were 1.54×10−6 cms−1 for oestradiol 17 β-D-glucuronide, 3.33×10−6 cms−1 for taxol, 20.8×10−6 cms−1 for quercetin, and 35.3×10−6 cms−1 for propranolol. For these four compounds, plasma on the basolateral side had no influence on absorption. However, plasma on the basolateral side significantly reduced the efflux of oestradiol 17 β-D-glucuronide by 66%, taxol by 75%, propranolol by 82%, and quercetin by 94%.

Failure to consider the effect of plasma binding can result in an overestimate of basolateral to apical efflux and result in misleading net flux calculations.
Antisecretory and Relaxatory Effects of Tachykinin Antagonists in the Guinea-pig Intestinal Tract
Authors: Goldhill Jon , Porquet Marie-France , Selve Norma
Published: October 2002

Existing models used to study the mechanism of action and antagonism of tachykinergic effects on intestinal contraction and secretion suffer from technical problems and have not been fully characterized using specific tachykinin antagonists. Contraction of ileal segments by substance P, colonic circular muscle by β-alanine-neurokinin A, and longitudinal muscle by senktide were used as models for neurokinin-induced contraction in the guinea-pig. Guinea-pig colonic epithelial tissue was stimulated by substance P and senktide to assess NK1- and NK3-mediated secretion. Using these models the potency of therapeutically useful compounds was determined.

NK1 and NK2 activation directly contracted smooth muscle, while NK1-mediated secretion was nerve-mediated. NK3 stimulation of contraction and secretion was neurally mediated, involving cholinergic nerves and 5-HT release. NK1-mediated contraction and secretion were antagonized by SR140333 (pD′2 = 9.29 and pKb = 8.53); NK2-mediated contraction was antagonised by SR48968 (pD′2 = 8.35) and NK3-mediated contraction and secretion were antagonized by SB223412 (pKb = 8.97 and 8.79). The mixed antagonist MDL103392 blocked NK1- and NK2-mediated contraction with pKb values of 7.92 and 6.71 respectively and NK1-mediated secretion with a pKb value of 6.57.

This data characterizes existing tachykinin antagonists, and should orientate the development of improved compounds as therapies for intestinal disease.
The Effect of Oren-gedoku-to on Experimental Colitis in Rats
Authors: Zhou Haiyan , Mineshita Satoru
Published: October 2002

In Japan and China, Oren-gedoku-to (a complex mixture of ingredients derived from plants) has been used as a herbal medicine in the treatment of inflammatory and ulcerative diseases. In other countries salicylazosulfapyridine has been used to treat inflammatory bowel disease. In this study, we have compared the effect of Oren-gedoku-to with salicylazosulfapyridine on trinitrobenzene-sulphonic acid-induced colonic damage in rats, a model representative of ulcerative colitis and Crohn's disease in man.

Oren-gedoku-to was administered orally for one or two weeks over a range of doses. Tissue damage scores, body weight, spleen weight, colon wet weight and colon wall thickness were measured, and colonic tissue levels of interleukin-8 (IL-8), leukotriene B4 (LTB4), prostaglandin E2 (PGE2), and myeloperoxidase activity were examined.

The results indicated that Oren-gedoku-to was effective in the treatment of inflammatory bowel disease in the rat model. Histological observation showed a quicker healing process of the lesions, and a reduction of inflammatory cell infiltration following administration of Oren-gedoku-to.

The precise mechanism of action for Oren-gedoku-to is still unclear; however, the reduction of IL-8, LTB4, and PGE2 observed suggests that the mechanism may be different from salicylazosulfapyridine (which has no effect on IL-8). There may be a potential benefit in offering combination therapy for the treatment of inflammatory bowel disease.
Effects of Sho-saiko-to Extract on Liver Fibrosis in Relation to the Changes in Hydroxyproline and Retinoid Levels of the Liver in Rats
Authors: Ono Masahide , Miyamura Mitsuhiko , Kyotani Shojiro , Saibara Toshiji , Ohnishi Saburo , Nishioka Yutaka
Published: October 2002

To examine the effects of Sho-saiko-to extract on liver fibrosis, the drug was administered to rats with dimethylnitrosamine-induced liver-injury at various doses. Hydroxyproline and retinoid levels in the liver were measured as indicators of liver function.

In liver-injured rats, the hydroxyproline level in the liver (957 ± 154nmol g−1) was about 4.16-times that found in normal liver (230 ± 11 nmol g−1), but administration of Sho-saiko-to extract (0.75%, 1.5% or 3%) reduced the hydroxyproline level significantly (554 ± 58, 356 ± 51, 374 ± 66 nmol g−1, P < 0.01). Single administration of the active constituents of Sho-saiko-to extract, glycyrrhizin, baicalin or baicalein, decreased the hydroxyproline level significantly compared with the ordinary food group (P < 0.05), but the decrease was smaller compared with the Sho-saiko-to extract group. The liver retinoid level was higher in the Sho-saiko-to extract group than the ordinary food group and the value increased dose-dependently. A significant negative correlation, r = −814 (P < 0.001) was detected between the hydroxyproline level and retinoid level in the liver of liver-injured rats. Significant negative correlations, r = 0.728 (P < 0.001) and r = −0.873 (P < 0.001), were also detected between the liver hydroxyproline level and the liver concentrations of the active constituents (glycyrretic acid, baicalin and baicalein) in the liver-injured rats.

From these findings, it was considered that the liver concentrations of hydroxyproline and retinoid as well as the active constituents were involved in the improvement of liver fibrosis in the liver-injured rats administered Sho-saiko-to extract. Administration of Sho-saiko-to extract inhibited collagen production while an increase in retinoid level inhibited activation of Ito cells leading to inhibition and prevention of liver fibrosis.
The Maximum Pharmacodynamic Effect as a Response Parameter: Pharmacokinetic Considerations
Authors: Leopold Claudia S
Published: October 2002

In previous human in-vivo studies measuring the maximum pharmacodynamic response to characterize cutaneously applied ointment preparations, it was observed that differences between various formulations caused by penetration enhancement led to different enhancement factors depending on the method used for determination of these factors from activity-reponse curves. To clarify this discrepancy, pharmacokinetic simulations have been performed based on an open one-compartment model with either first- or zero-order drug penetration kinetics and first-order elimination kinetics.

Under the assumption that the maximum pharmacodynamic response corresponds to the maximum effective drug concentration in the receptor compartment, which represents the difference between the maximum drug concentration and the threshold concentration, drug concentration vs time profiles and dose-reponse curves were simulated. In addition, maximum effective concentrations were calculated and plotted against the logarithm of the thermodynamic drug activity to obtain activity-reponse curves. Relative bioavailability and enhancement factors were determined either from the horizontal distance between the curves of a standard and a test preparation, or as the ratio of the maximum effective concentration of test and standard formulations.

A significant difference between the first-order and the zero-order input kinetics with regard to the evaluation of bioavailability and drug penetration enhancement was shown. Under finite dose conditions, i.e. first-order input kinetics from solution-type preparations, a misestimation of the factors usually occurs. Only under infinite dose conditions, i.e. if large preparation volumes are applied to achieve zero-order input kinetics, is the determination of bioavailability and enhancement factors from dose- and activity-reponse curves accurate.
Age-related Alteration of Carbamazepine-serum Protein Binding in Man
Authors: Koyama Hikaru , Sugioka Nobuyuki , Uno Akira , Mori Satoru , Nakajima Kenji
Published: October 2002

To determine whether biological maturation influences the kinetics of carbamazepineserum protein binding, the carbamazepine free fraction (%) was investigated in the serum of 66 patients, ranging from 4 to 83 years, with epilepsy or trigeminal neuralgia, treated with carbamazepine alone or carbamazepine in combination with phenytoin, phenobarbital, and/or valproic acid, over a relatively long period.

Biochemical parameters such as levels of albumin and non-glycated albumin showed a significant relationship with carbamazepine free fraction (r=-0.521, P < 0.001 for albumin; r=-0.700, P < 0.001 for non-glycated albumin). Non-glycated albumin was more strongly correlated with carbamazepine free fraction. The biochemical parameters showed a significant relationship with age (r=-0.243, P < 0.1 for albumin; r= 0.666, P < 0.001 for glycated albumin; r=-0.459, P < 0.001 for non-glycated albumin; r= 0.640, P < 0.001 for carbamazepine free fraction). Glycated albumin (%), non-glycated albumin and carbamazepine free fraction (%) were strongly correlated with age, whereas albumin showed only a weak correlation with age. To evaluate the effects of ageing on carbamazepine-serum protein binding, the patients were divided into three groups according to age: children, 4–15 years; adults, 16–64 years; elderly, 65–83 years. Albumin and non-glycated albumin were much lower, and glycated albumin (%) and carbamazepine free fraction (%) much higher in the elderly group than in the other two groups.

The results of this study showed that the major ligand of carbamazepine in the serum was non-glycated albumin, which decreased with age. These observations suggested that in elderly patients, the elevation of free carbamazepine concentrations in the serum caused by reduced non-glycated albumin levels, induces increases in the sensitivity of the pharmacological effects of carbamazepine and the risk of drug interactions.
An In-vitro Study on the Metabolism of Rokitamycin and Possible Interactions of the Drug with Rat Liver Microsomes
Authors: Zhao Xue-Jun , Ishizaki Takashi
Published: October 2002

This in-vitro study was designed to identify the enzyme(s) involved in the major metabolic pathway of rokitamycin, i.e. the formation of leucomycin A7, and to assess possible interactions of the drug with rat liver microsomes.

Formation of leucomycin A7 was NADPH-independent and was not appreciably inhibited by anti-rat NADPH cytochrome P-450 reductase serum or cimetidine, a nonspecific inhibitor of cytochrome P-450 isoforms. Eadie-Hofstee plots for the formation of leucomycin A7 were indicative of apparently monophasic behaviour for six rat liver microsomes tested. The mean (± s.d.) kinetic parameters, Km, Vmax and Vmax/Km, for the formation of leucomycin A7 from rokitamycin were 47 ± 13 μm, 390 ± 56 nmol min−1 (mg protein)−1 and 8.6 ± 1.6 mL min−1 (mg protein)−1, respectively. Three esterase inhibitors (100 μM), bis-nitrophenylphosphate, physostigmine and metrifonate inhibited the formation of leucomycin A7 by more than 60%. Metabolism of rokitamycin was inhibited by terfenadine, but not by mequitazine, whereas chlorpheniramine and theophylline activated the formation of leucomycin A7. Rokitamycin, leucomycin A7, leucomycin V, erythromycin and clarithromycin were weak inhibitors of CYP3A-catalysed 3-hydroxylation of quinine with mean IC50 values ranging from 71 to > 100 μM.

It is concluded that in rat liver microsomes the formation of leucomycin A7 from rokitamycin is catalysed mainly by an esterase (possibly cholinesterase, EC3.1.1.8), but not by cytochrome P-450 enzyme(s). Although in this in-vitro animal study CYP3A activity was barely inhibited by rokitamycin, the possibility cannot be totally discounted in man when rokitamycin is co-administered with drugs metabolized by CYP3A.
Differences between the Vasorelaxant Activity of Adenosine-receptor Agonists on Guinea-pig Isolated Aorta Precontracted with Noradrenaline or Phenylephrine
Authors: Ford William R , Maddock Helen L , Buckingham Robin E , Broadley Kenneth J
Published: October 2002

The relaxant effect of adenosine and 5′-(N-ethylcarboxamido)adenosine (NECA) against α-adrenoceptor-mediated contractile tone in guinea-pig isolated aortic rings has been examined to determine if this A2B-receptor-mediated relaxation was dependent upon the contracting agent, and whether the contractions were dependent upon intracellular or extracellular calcium.

Relaxation responses were consistently greater for aortic rings pre-contracted with phenylephrine (3 times 10−6M) than for rings pre-contracted with noradrenaline (3 times 10−6M). Maximum inhibition by NECA was significantly greater for phenylephrine-contracted aortae than for noradrenaline-contracted (81.9 ± 2.8% compared with 25.0 ± 1.5%). These differences persisted in the presence of β- and α2-adrenoceptor blockade and could not, therefore, be attributed to stimulation of these receptors by noradrenaline. The ratio of the contractions obtained before and in the presence of adenosine or NECA was compared with the control ratio obtained before and after vehicle. Experiments were performed both in the presence of normal calcium levels and under calcium-free conditions. In normal-calcium medium, NECA inhibited phenylephrine-induced contractions (test ratio, 76.7 ± 3.9%; control ratio, 133.1 ± 9.8%) to a greater extent than noradrenaline-induced contractions (108.4 ± 4.1 and 123.4 ± 4.9%); adenosine similarly inhibited phenylephrine-induced contractions more than those induced by noradrenaline. Under calcium-free conditions, adenosine (36.7 ± 11.9 and 110.7 ± 26.6%) and NECA (55.2 ± 9.1 and 87.1 ± 14.9%) were only effective against phenylephrine-induced contractions. This suggests that activation of the A2B-receptor by these agonists inhibited intracellular mobilization of calcium for phenylephrine-induced contractions only. The effects on extracellular calcium influx were examined for phenylephrine- and noradrenaline-induced contractions in normal-calcium medium but in the presence of ryanodine to prevent intracellular calcium mobilization. NECA inhibited phenylephrine-induced contractions (77.3 ± 12.4 and 111.4 ± 9.3%), presumably by interfering with influx of calcium through receptor-operated calcium channels. In contrast, NECA failed to reduce noradrenaline-induced contractions (121.5 ± 10.7 and 122.4 ± 11.6%), suggesting that the effect on noradrenaline is predominantly via interaction with intracellular calcium. Adenosine was consistently a more effective relaxant than NECA, possibly because of an additional intracellular component of the response.

We conclude that adenosine receptor agonists inhibit phenylephrine-induced contractions of guinea-pig aorta more selectively than noradrenaline-induced contractions. A2B-receptor stimulation might reveal a fundamental difference between the modes of contraction elicited by these two α-adrenoceptor agonists.
Himehabu Lectin, a Novel Inducer of Ca2+-release from the Venom of the Snake Trimeresurus okinavensis, in Sarcoplasmic Reticulum
Authors: Hirata Yutaka , Ito Masaaki , Nikai Toshiaki , Kato Saori , Komori Yumiko , Sugiura Hisayoshi , Ohizumi Yasushi
Published: October 2002

The lectin himehabu lectin (HHL) has recently been isolated from crude venom of the snake Trimeresurus okinavensis.

Ca2+-electrode and fluorescent Ca2+-indicator experiments showed that HHL induced release of Ca2+ from the heavy fraction of skeletal muscle sarcoplasmic reticulum (HSR). The release of Ca2+ induced by caffeine from HSR was abolished by ryanodine, Mg2+ and ruthenium red, typical inhibitors of Ca2+-release channels, whereas that induced by HHL was only partially reduced by these inhibitors. HHL, unlike caffeine, had no effect on [3H]ryanodine binding to HSR.

These results suggest that HHL induces release of Ca2+ which is at least partially mediated through Ca2+-release channels with novel pharmacological properties.
Validation of a Pharmacokinetic Model of Colon-specific Drug Delivery and the Therapeutic Effects of Chitosan Capsules Containing 5-Aminosalicylic Acid on 2,4,6-Trinitrobenzenesulphonic Acid-induced Colitis in Rats
Authors: Tozaki Hideyuki , Fujita Takuya , Odoriba Tomokazu , Terabe Akira , Okabe Susumu , Muranishi Shozo , Yamamoto Akira
Published: October 2002

A pharmacokinetic model of colon-specific drug delivery developed in a previous study has been validated by use of 5-aminosalicylic acid (5-ASA) as a model anti-inflammatory drug.

The simulation curves obtained from the pharmacokinetic model were in good agreement with experimental data obtained after oral administration of 5-ASA-containing chitosan capsules. The concentrations of 5-ASA in the large intestinal mucosa after drug administration were higher than after administration of the drug in carmellose suspension. We then attempted colon-specific delivery of an anti-ulcerative colitis drug, in chitosan capsules, to accelerate healing of 2,4,6-trinitrobenzenesulphonic acid sodium salt (TNBS)-induced colitis in rats. To confirm this therapeutic model, salazosulphapyridine (SASP), a commercially available 5-ASA prodrug, was used as positive control. Colonic injury and inflammation were assessed by measuring myeloperoxidase activity and visual assessment (damage score), respectively. Because SASP is effective against TNBS-induced colitis in rats, use of the SASP-sensitive TNBS-induced colitis model validated the therapeutic effects of 5-ASA-containing chitosan capsules, which were signiicantly better than those of a suspension of the drug in carmellose.

These findings suggest that our pharmacokinetic model of colon-specific drug delivery can accurately evaluate this colon-specific delivery system and that 5-ASA-containing chitosan capsules are more effective than other 5-ASA formulations for treatment of TNBS-induced colitis in rats.
Enterohepatic Circulation Model for Population Pharmacokinetic Analysis
Authors: Funaki Tomoo
Published: October 2002

An enterohepatic circulation model based on physiological aspects of biliary excretion has been developed for population pharmacokinetic analysis. Mycophenolate mofetil was selected as a model drug for validation of the model. As a secondary objective, the model was used for pharmacokinetic comparison among different races.

The post-hoc plasma concentration-time course was well described by the newly developed enterohepatic model and a secondary peak arising from enterohepatic circulation was also well defined. The covariates predicted by the model agreed well with literature results.

The model is useful for evaluation of the covariates of an enterohepatically circulated drug. The population pharmacokinetic approach is of benefit for evaluating racial differences for a pharmacokinetic bridging package.
Application of a Loading Wash-out Method for Investigating the Hepatocellular Efflux of a Hepatically-generated Metabolite, Morphine-3-glucuronide
Authors: Evans Allan M , O'Brien Josephine , Nation Roger L
Published: October 2002

Previous studies using the rat isolated perfused liver demonstrated that the hepatic disposition of morphine-3-glucuronide is membrane permeability-rate limited, and that the movement of the metabolite across hepatic sinusoidal and canalicular membranes is partly via carrier-mediated transport systems. As a consequence of the membrane permeability-limitation, the biliary excretion of hepatically-generated morphine-3-glucuronide is much more efficient than that of morphine-3-glucuronide reaching the liver via the vasculature. We have quantitated the cellular efflux kinetics (cell-to-blood and cell-to-bile) of morphine-3-glucuronide in the rat isolated perfused liver using a loading wash-out design. In the ‘loading’ phase, morphine was infused into the liver (2.7 μM) and the biliary excretion and sinusoidal efflux of morphine-3-glucuronide was assessed under steady-state conditions. Subsequently, the infusion was stopped and the concentration vs time profile of morphine-3-glucuronide in outflow perfusate (the wash-out phase) was determined. A physiologically-based pharmacokinetic model was used to determine the rate-constants for the movement of hepatically-generated morphine-3-glucuronide into the sinusoidal and canalicular spaces of the liver, and the associated membrane permeability terms.

The mean (±s.d.) rate constants for the biliary excretion and sinusoidal efflux of morphine-3-glucuronide were determined to be 0.160±0.043 and 0.169 ± 0.068 min−1, respectively, and the corresponding membrane permeability parameters were 1.12 and 1.18 mL min−1, respectively. The sinusoidal membrane permeability term was significantly less than hepatic blood flow in the rat. The volume of distribution of hepatically-generated morphine-3-glucuronide (207.5 ± 74.8 mL) was found to be approximately 50-times the intracellular space of the rat liver, suggesting that hepatically-generated morphine-3-glucuronide accumulates within hepatocytes. The results indicate that hepatically-generated morphine-3-glucuronide undergoes intracellular accumulation, probably as a consequence of poor membrane permeability.
Novel Weight-Reducing Activity ofGalega officinalisin Mice
Authors: Palit P , Furman B L , Gray A I
Published: October 2002

Galega officinalis (galega, Goat's Rue, French Lilac) is well known for its hypoglycaemic action and has been used as part of a plant mixture in the treatment of diabetes mellitus. During pharmacological investigations of an ethanolic extract of a powdered mixture of equal proportions of G. officinalis, Cressa cretica, Mangifera indica and Syzygium jambolanum, a weight reducing effect of galega was discovered. In this study we have investigated the novel weight reducing effect of galega in mice.

Galega herb (10% w/w in the diet) caused a significant reduction in body weight in both normal and genetically obese (ob/ob) animals treated for 28 days when compared with respective controls (P < 0.01). In normal mice, the weight loss was reversible and initially associated with a transient reduction in food intake but was then maintained even in the presence of increased eating above the control level. Pair-fed normal mice receiving galega for seven days also showed significant weight loss (P < 0.01, compared with the control) in the presence of increasing food intake. In sharp contrast, weight loss in galega-treated ob/ob mice was accompanied by a persistent reduction in food intake over the 28-day treatment period. Post-mortem examinations of all galega-treated mice revealed a striking absence of body fat. Serum glucose was significantly reduced in both strains of mice receiving galega for 28 days (P < 0.01), whereas serum insulin was significantly reduced only in obese mice (P < 0.01).

In summary, together with its established hypoglycaemic effects, galega has a novel weight reducing action that, in normal mice, is largely independent of a reduction in food intake. The mechanism of the weight reducing action of galega is unclear but involves loss of body fat.
Effects of Green Tea Tannin on Cisplatin-induced Nephropathy in LLC-PK1 Cells and Rats
Authors: Yokozawa Takako , NAKAGAWA Takako , Lee Kyeoung Im , Cho Eun Ju , Terasawa Katsutoshi , Takeuchi Shigeya
Published: October 2002

A study was conducted to clarify whether green tea tannin ameliorated cisplatin-induced renal injury in terms of lactate dehydrogenase and malondialdehyde leakage from a renal epithelial cell line, swine-derived LLC-PK1 cells in culture. Green tea tannin was shown to suppress the cytotoxicity of cisplatin, the suppressive effect increasing with the dose of green tea tannin. The effect of cisplatin was then investigated in rats given green tea tannin for 40 days before cisplatin administration and in control rats given no green tea tannin.

In control rats, blood, urinary and renal parameters and the activities of antioxidative enzymes in renal tissue deviated from the normal range, indicating dysfunction of the kidneys. In contrast, rats given green tea tannin showed decreased blood levels of urea nitrogen and creatinine, and decreased urinary levels of protein and glucose, reflecting less damage to the kidney. In this group, the activity of catalase in the renal tissue was increased, while the level of malondialdehyde was decreased, suggesting the involvement of radicals in the normalizing of kidney function.

Based on the evidence available it appeared that green tea tannin eliminated oxidative stress and was beneficial to renal function.