Antiradical Activity of Hydrolysates and Extracts from Mollusk A. broughtonii and Practical Application to the Stabilization of Lipids

The antiradical properties of hydrolysates and hydrothermal extracts of bivalve mollusks (Anadara broughtonii) from the Far Eastern Region of Russia and their influence on lipid oxidation in mayonnaise were investigated. The radical binding activity of hydrolysates and extracts of A. broughtonii varies from 55% to 89%. The maximum radical-binding activity was observed for acid hydrolysates. The antiradical efficiency of acid hydrolysates is 35%–41% of the BHT (butylhydroxytoluene) index. The antiradical activity depends on the (method of) technological and biotechnological processing of raw materials. Acid and enzymatic hydrolysates and hydrothermal extracts of A. broughtonii in mayonnaise slow down the process of oxidation of lipids and hydrolysis of triglycerides. Acid hydrolysates reduce the speed of oxidation and hydrolysis of lipids in mayonnaise more efficiently than the enzymatic hydrolysates.

The proteome analysis of rat platelet with nano-liquid chromatography-matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technique

Recently, the proteomic analysis has become an ideal tool to study the structure and function of platelets. We proposed a nano-liquid chromatography (nano-LC) technique coupled off-line with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) for rat platelet proteome analysis. In this study, we attempted to analyze the rat platelet proteome in two different subcellular fractions: cytosol and membrane. Platelet-rich plasma was collected from healthy rats. The platelet samples were extracted with Subcellular Proteome Extraction Kit to collect subcellular compartments. For further investigations, platelet lysate, cytosol and membrane fractions were used. Enzymatic digestion of proteins was performed using Filter Aided Sample Preparation method with trypsin as a proteolytic enzyme. Tryptic peptides were analyzed using nano-LC-MALDI-TOF/TOF-MS. Platelet proteins identification was performed using the Mascot engine. We identified 238 proteins in the platelet lysate, 210 in the cytosol, and 148 in the membrane fraction. Among them, 45 were unique for platelet lysate, 55 for cytosol, and 34 for the membrane fraction. The gene ontology analysis showed that there were differences in the proteome of cytosol and membrane fractions related to the molecular functions, i.e. coagulative activity. Our results may suggest that the membrane or cytosol location of the proteins with coagulative activity may be responsible for the acute or delayed platelet response to an agonist. The nano-LC-MALDI-TOF/TOF-MS method can be used for identifying proteins of subcellular fraction in rat platelets.

Diazepam and its metabolites in the mothers' and newborns' hair as a biomarker of prenatal exposure

Pregnant women are exposed to benzodiazepines for therapeutic purposes during gestation. The goal of this study was to evaluate prenatal exposure to benzodiazepines. Time of exposure during course of pregnancy is a significant aspect of fetal exposure to drugs. Benzodiazepine concentration assay in hair of mothers and newborns exposed prenatally to these drugs was performed in the studies. Development, validation and evaluation of benzodiazepine determination method in mothers and their newborns enables assessment of health risks for the child and implementation of adequate therapeutic procedures. We used A LC-ESI-MS/MS method that allowed determination of diazepam (the main benzodiazepine used by pregnant women was diazepam) and its metabolites (nordazepam, oxazepam) in hair of mothers and newborns. LOQ 10 pg/mg of hair was used in the study.

RESULTS

concentration of nordazepam was higher than parent drug (diazepam) and higher in newborns' hair when compared to mothers'. The mean concentrations of diazepam in mothers' hair were 31.6±36.0 and 34.1±42.4 pg/mg in the second and third trimester of pregnancy respectively. The mean concentration of diazepam in newborns' hair was higher and reached levels of 53.3±36.5 pg/mg. The mean concentration of nordazepam in the mothers' hair corresponding to the second and third trimester was 52.9±48.1 and 89.9±122.8 pg/mg, respectively. Nordazepam in the newborns' hair was detected at the mean level of 108.1±144.2 pg/mg. It was concluded that diazepam and nordazepam are permanently incorporated into the hair structure. Presence of diazepam and its metabolites in newborn's hair confirms that these benzodiazepines permeate placental barrier. Segmental analysis of mothers' hair enabled the assessment of drug administration time. Diazepam and its metabolites determined in hair of newborns may serve as biomarkers of prenatal exposure to these drugs. The performed LC-MS/MS analysis was accurate enough to determine even low concentrations of benzodiazepines, at the level of few pg/mg of hair. Levels of diazepam detected in hair of newborns were higher than levels determined in mothers. This may confirm the fact, that fetus's ability to metabolize diazepam is scarce. Nordazepam was found in higher concentrations in hair of newborns than in hair of mothers, which may suggest that it is cumulated in child's organism. Other metabolites of diazepam--oxazepam and temazepam--were detected in very few cases, in low concentrations.

Influence of tobacco smoke on the pharmacokinetics of citalopram and its enantiomers

The purpose of this study was to evaluate the influence of tobacco smoke on the pharmacokinetics of citalopram (CIT) and desmethylcitalopram (DCIT) and its enantiomers on an animal model. High performance liquid chromatography (HPLC) with a diode array detector (DAD) was used for the identification and quantification of the studied compounds. The HPLC quantification of racemic mixtures of CIT was performed on a C18 column. The limits of detection (LOD) and quantification (LOQ) were: 7 and 10 ng/ml respectively. HPLC separation of citalopram enantiomers (S- and R-CIT) was performed on a Chirobiotic V column. The limits of detection (LOD) and quantification (LOQ) were: 6 and 15 ng/ml for R- and S-CIT respectively. The experiment was carried out on male Wistar rats. The rats were exposed to tobacco smoke for five days (6 hours per day). After the exposure, citalopram was administered in a dose of 10 mg/kg intragastrically. In the control group (non-exposed animals), citalopram was administered in the same way and at an equal dose. The blood of the animals was collected at nine time points. It was found that tobacco smoke exposure inhibits the biotransformation of citalopram. The half-life of the racemic mixture of citalopram after intragastric administration was increased by about 287%. Changes in the pharmacokinetic parameters of S-citalopram (active isomer) show a similar tendency to those of the racemic mixture. The pharmacokinetics of R-citalopram showed no statistically important differences after tobacco smoke exposure. Alterations in the pharmacological parameters of desmethylcitalopram presented an opposite trend to the parent drug. After exposure to tobacco smoke, the induction of metabolism of this compound was observed.

Effect of maternal tobacco smoking or exposure to second-hand smoke on the levels of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in urine of mother and the first urine of newborn

Tobacco smoking during pregnancy is associated with a variety of negative consequences not only for the mother, but also for the developing fetus. Many studies have shown that carcinogens contained in tobacco smoke permeate across the placenta, and are found in fetus. The aim of the study was to determine the prenatal exposure to tobacco-specific carcinogenic N-nitrosamines on the basis of measurements of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in urine of smoking and second-hand smoke (SHS) exposed women and in the first urine of their newborns. A questionnaire documenting demographics and socio-economical data, smoking habits and exposure to SHS was completed by 121 delivering women near or at term. Maternal concentrations of cotinine and NNAL were measured in urine of the mother and the first urine of her newborn infant by liquid chromatography tandem mass spectrometry (LC/MS/MS). The mean concentration of cotinine was 439.2 ng/mg creatinine and NNAL concentration in urine of smoking women was 74.0 pg/mg creatinine, and for her newborn 78.6 pg/mg creatinine. Among mothers exposed to SHS, cotinine and NNAL mean concentration were 23.1 ng/mg creatinine, and 26.4 pg/mg creatinine. In newborns of SHS exposed mothers during pregnancy the mean concentration of NNAL was 34.1 pg/mg creatinine, respectively. Active tobacco smoking as well as passive exposure to smoking during pregnancy is an important source of tobacco specific N-nitrosamines to the fetuses as evidenced by increased concentrations of this carcinogen. Determination of NNAL in maternal urine samples can be a useful biomarker of prenatal exposure of newborn to carcinogenic nitrosamines.

The influence of simultaneous whole body exposure to cigarette smoke and low-protein diet feeding on fertility, reproduction, and progeny of rats

The aim of the present study was to evaluate the toxicological influence of different concentrations of tobacco smoke and low-protein diet on fertility, reproduction, and survival of offspring of Wistar female rats. We studied three generations, two litters in each. There were 192 animals in parent generation. Animals were exposed to three different concentrations of tobacco smoke that were reflected by the carbon monoxide (CO) concentration (500, 1000, and 1500 mg CO/m3 air) during 11 weeks (six before and two weeks during mating, and three weeks of pregnancy). Additionally, animals were divided into two subgroups that were fed normal or low-protein diet. In the present study, we concentrated on the indices describing the reproduction ability, fertility, and rearing of pups of mothers exposed to tobacco smoke. The parameters of newborns survival were estimated also. We concluded that neither tobacco smoke exposure nor the low-protein diet changed the duration of pregnancy. The tobacco smoke in all doses and low-protein diet had a negative influence on fertility, reproduction, and survival of newborns from exposed mothers. This influence was mainly attributed to the tobacco smoke exposure. The levels of carboxyhaemoglobin were increasing with increasing tobacco smoke concentration.

The clinical value of the determinations in the serum of zinc concentration in women with breast cancer

The clinical usefulness of the determinations of the zinc serum concentration at different stages of the breast cancer diagnostic process was evaluated in the present work. On the basis of the analysis of 182 women surgically treated because of this neoplasm, a statistically significant dependence was shown between the frequency of occurrence of hypozincemia and the progression of the cancer, its histological form, and the microscopic state of the axillary lymph nodes. The clinical usefulness was also shown by the determinations of the zincemia in the post-operative monitoring of patients with breast cancer. The critical value was also determined for the microelement concentration below which a statistically significantly high risk of occurrence of distant metastases appears.

Endogenous diazepam concentrations in the serum of patients with liver neoplasms

The study included 61 patients (35 men and 26 women) ages 47 to 74 in whom a primary liver cancer was diagnosed or neoplastic metastases to the liver were confirmed in the course of a cancer of the stomach or the large bowel. In each patient the endogenous serum diazepam concentration (ESDC) was estimated chromatographically and the results obtained were compared to selected clinical traits such as the magnitude and number of neoplastic changes and their location in the liver parenchyma, the histological form of the tumor and the primary location of the cancer in the case of neoplasms of the alimentary canal. The determination of the ESDC was also carried out in a control group made up of voluntary blood donors. Neither group examined received any medication belonging to the benzodiazepine group. From the results of the tests conducted it was confirmed that the average ESDC of patients with liver neoplasms was 65 times higher than that of the control group. Simultaneously, however, in patients with a primary liver cancer the average endogenous concentration was higher than in patients with neoplastic metastases to that organ and this was statistically significant. The location in the hepatic parenchyma of the neoplastic change as well as the primary location of the cancer remained without a statistically significant influence in the changes of ESDC. It was moreover shown that significantly high ESDC were associated in the liver mainly with increased neoplastic growth (above 3 cm in diameter) and with multiple spread (5 focuses and more).

Determination of opiates in serum, saliva and hair addicted persons

In the last ten years advances in analytical methods have enabled the determination of xenobiotics in alternative material such as sweat, saliva, and hair. The aim of this study was to develop an analytical method and measure the concentration of the main opiates in serum saliva and hair of subjects from a detoxification and methadone treatment programme. The analytical strategy in the presented study, based on enzymoimmunoassay screening of opiates in urine and GC/MS confirmation, meets the needs of forensic and clinical toxicology. Blood and saliva samples from thirty seven patients and hair from twenty three with a history of intravenous opiate use were collected for analysis. The ranges of morphine in serum and saliva were 0-2081 and 0-208 ng/ml respectively; corresponding concentrations of codeine were 0-580 and 0-428 ng/ml respectively. The concentration of morphine, codeine and 6-MAM in hair of addicts ranged respectively from 0-32.4, 0-12.5 and 0-2.8 ng/mg. From the clinical toxicology point of view, hair analysis is supplementary to urine, serum or saliva determination, but in drug testing at the workplace it can play a crucial role.

The bacterial flora and the changes of the N-nitrosamine concentration in the operated stomach

The studies included 170 patients (103 men and 67 women) aged 23 to 66 years, operated on because of an ulcerous disease. Depending on the method of surgical treatment patients were divided into 5 groups (those after gastric resection with Rydygier's method, after resection with the Billroth II method, after trunk vagotomy with pyloroplasty, after highly selective vagotomy, and after gastro-enterostomy). In all patients a qualitative estimation of the nitrate-reducing bacteria was carried out, as well as a chromatographic test of the selected N-nitrosamine concentration in the gastric juice. It was shown that the changes in the quantity of the nitrate-reducing bacteria and in the N-nitrosamine concentration depended on the type of surgical intervention conducted. The largest mean content of nitrate-reducing bacteria and the highest average N-nitrosamine concentration were confirmed in the gastric juice of patients after gastroenterostomy and after gastric resection with the Billroth II method, and the lowest values--in patients after highly selective vagotomy.

[Profile of chemical analyses of psychoactive substances in the Laboratory of the Department of Clinical Toxicology in the years 1990-1999]

The chemical-toxicological Laboratory of the Department of Clinical Toxicology carry on the analyses of xenobiotics in biological fluid collected from poisoned patient leaving in Krakow and south-eastern Poland. The evaluation of frequency of performed analyses in the years 1990-1999 shown that among psychoactive substances, ethanol is the most common reason of acute poisoning, followed by psychotropic drugs and drugs of abuse. The level of ethyl alcohol above 2 g/L was observed in more than 40% of patients. In evaluated period the number of barbiturates analyses dropped, benzodiazepines stayed on the same level. During this time evident increase of illicit drugs (amphetamines, opiates and THC) analyses was observed.

[Concentration of zinc, copper and magnesium in the serum of drug addicts]

The aim of this study was to determine the concentration of zinc, copper and magnesium in the blood serum of drug addicts in order to ascertain whether drug abuse has an effect on the concentration of these metals. The study was carried out on a group of 33 addicts undergoing treatment at the Department of Clinical Toxicology, Collegium Medicum, Jagiellonian University in Kraków. The control group consisted of 22 young, healthy, drug free, male volunteers. Analyses were performed using flame atomic absorption spectrometry. The results demonstrate that zinc serum concentrations in the examined group of addicts before therapy (mean 0.82 mg/l) were reduced in relation to the control group (mean 1.12 mg/l), and was slightly enhanced after the detoxification process (mean 0.86 mg/l). The opposite effect was observed in the case copper serum concentration. The copper level in the group of addicts on admission to hospital (mean 1.35 mg/l) increased in relation to the control group (mean 1.11 mg/l) and was lower during hospitalisation (mean 1.18 mg/l). The concentration of magnesium in the serum of drug addicts did not change during therapy and was in the same range as in the control group (mean concentrations were 20.3 mg/l, 20.2 mg/l and 20.6 mg/l respectively).

Inter- and intra-individual variability of ethanol pharmacokinetics over a long period of time

In most research, the inter- and intra-individual variability of time profiles of ethanol concentration has been studied over a relatively short period of time. We present a study of inter- and intra-individual variability of ethanol pharmacokinetics in five healthy volunteers (social drinkers) over a period of around eight years. The volunteers received a dose of 0.7 g/kg (men) and 0.6 g/kg (women) of ethanol in the form of vodka diluted with mineral water. The blood ethanol concentrations in a series of samples were measured by gas chromatography. For pharmacokinetic calculations, a model with first-order absorption and Michaelis-Menten elimination was applied. A linear regression technique was used to calculate Widmark's coefficient. The area under the concentration-time curve (AUC) was calculated by trapezoid rule. A tendency for pharmacokinetic parameters to alter during the study time was observed, however, these changes were random and did not correlate with the duration of the study. The highest inter- and intra-subject variability of the half time of absorption was observed. The maximal elimination velocity and Michaelis-Menten constant were also very unstable; coefficients of variation were 55.8% and 79.0%, respectively. Other calculated pharmacokinetic parameters (AUC, beta60, V/F, Cmax) were characterized by a lower variability with a coefficient of variation around 36%. Back extrapolation of plasma ethanol concentration using mean value of beta60 for each subject showed that results could be underestimated up to 26% or overestimated up to 102%.

Changes in serum copper level during detoxification of acutely poisoned drug addicts

Although it is known that drug addicts are a high-risk group for disruption of many homeostatic processes, little is know about changes in serum trace elements concentrations after taking the psychoactive substances. The aim of the study was to check the influence of the taking homemade heroin on serum level of copper. Blood samples were taken from 30 opiate addicts, and copper concentrations were measured by the means of atomic absorption spectrophotometry. The result of the study show that in the examined group, copper serum concentrations (1.35 mg/L) upon admission to the clinic were higher than in the control group (1.11 mg/L) but decreased during hospitalization (1.18 mg/L). There was no correlation between duration of stay at the hospital and changes in serum copper concentration.

Chronopharmacokinetics of amitriptyline in rats

The circadian changes in absorption, tissue distribution and elimination of amitriptyline after single intravenous (i.v.) and intragastric (i.g.) administration, as well as the differences in pharmacokinetic profile after multiple i.g. administration (at 10:00 and 22:00 h) during a 12 h dosing interval, were investigated. The circadian changes of pharmacokinetic parameters of amitriptyline such as AUC (serum and tissues), clearance (i.v. and i.g.), volume of distribution, biological half-life and bioavailability were estimated. Acrophases for clearance appeared between 19:00 and 21:00 h; the bioavailability was highest during the dark phase at around 04:00 h. Higher values of AUC in serum were observed at the beginning of the light phase. A circadian rhythm of tissue distribution (AUC, K(D)) of amitriptyline with acrophase in the dark phase was observed for brain (12 h period), lung and liver (24 h), but not for heart or kidney. After single (i.v. and i.g.) amitriptyline administration, concentrations of its major metabolite, nortriptyline, were negligible; however, after ten doses, nortriptyline serum and tissue levels were similar to the concentrations of the parent drug with higher values during the day (light phase).

[Acute oral poisoning with isopropyl alcohol in alcoholics]

The symptoms and clinical course of repeated poisonings with isopropyl alcohol in ethanol addicted 43-years old man is presented in the study. The blood and urine concentrations of isopropanol and acetone and also the blood ethanol concentration are given. The biological half-life of isopropanol calculated for the first 12 hours from admission to the Clinic was 6.9 hours. The biological half-life of acetone in the first 6 hours of hospitalisation was 5 hours, and then a considerable slowing down up to 29 hours was noted. The clinical symptoms, similar to ethanol poisoning, including strongly manifested catatonia and ketonuria without metabolic acidosis indicate the isopropanol intoxication. Hypokalemia should to be taken into consideration in treatment of isopropanol poisoning. An intravenous bicarbonates should be administered carefully e.g. when rhabdomyolysis occur.

Effect of ethanol dose on its chronopharmacokinetics in the rats

Circadian changes in the elimination of ethanol after its administration in the rats in two doses: low (1.5 g/kg) and high (4.5 g/kg) were investigated. Circadian rhythm in ethanol pharmacokinetics (AUC, CLpo, t1/2) was observed after the low dose but not after the high one. The maximum rate of elimination was in the dark (active) phase at 1 am. The maximum value of clearance was related to the minimum value of AUC. Although the maximum and the minimum values of Vmax and KM differed essentially the diurnal variation were not observed.

Effect of hematocrit and albumin concentration on hepatic clearance of tacrolimus (FK506) during rabbit liver perfusion

Tacrolimus is an immunosuppressive agent used for organ transplantation. Studies were performed to examine the influence of different perfusate hematocrits and albumin concentrations on hepatic extraction of tacrolimus. In vitro binding, efflux and influx between red blood cells (RBCs) and buffer or plasma, and rabbit liver perfusion with use of human erythrocytes were studied. In the range of hematocrits from 0.05 to 0.4, plasma concentrations of tacrolimus were not affected by increased albumin content. Increased hematocrit caused decreases in whole blood:plasma (buffer) concentration ratios. The binding capacity of drug with RBCs was independent of hematocrit, with a value of 440 ng/ml of RBCs; the binding affinity was 0.876 ng/ml using plasma or buffer. Diffusion of tacrolimus from RBCs to buffer was rapid with a clearance of 0.940 ml/min, and equilibration was achieved within 2 min. Diffusion in the opposite direction (buffer-RBCs) was slower with a clearance of 0.576 ml/min. In such diffusion studies, plasma produced a greater difference between efflux (1.70 ml/min) and influx (0.276 ml/min) clearances. During liver perfusion, the major factor regulating elimination of tacrolimus was hematocrit. Both well-stirred and parallel-tube models reflected a low extraction ratio drug with values of 0.15 and 0.17 for the 0.05 and 0.2 hematocrits. Intrinsic clearances were 8.43 and 17.44 ml/min for the well-stirred and parallel-tube models. Albumin had a negligible influence on liver extraction of drug. A model-building process of characterizing nonlinear RBC binding, RBC diffusion rates, and liver perfusion parameters allows the complexities of tacrolimus hepatic clearance to be dissected and shows that strong RBC binding can be artificially perceived as causing a high clearance of the drug.

Pharmacokinetics of tacrolimus in liver transplant patients

OBJECTIVE

To characterize the pharmacokinetics of the immunosuppressive agent tacrolimus (FK 506) in liver transplant patients.

METHODS

Patients (n = 16) were assessed during and after 1- to 3-day intravenous infusions followed by a 2-week course of oral dose therapy. Plasma and whole blood data were fitted simultaneously with equations accounting for nonlinear drug binding by red blood cells to generate clearance (CL) and volume of distribution (V).

RESULTS

The maximum blood/plasma ratio of tacrolimus was 55.5 +/- 26.8 (SD) and half-life averaged 12.1 +/- 4.7 hours. The CL and V were relatively high based on plasma concentrations (CL, 1.7 L/hr/kg; V, 30 L/kg) and low based on whole blood (CL, 54 ml/hr/kg; V, 0.9 L/kg), with moderate variability (coefficient of variation, 34% to 49%) among the patients. Correlations of plasma CL and V with maximum blood/plasma ratios (ranging from 13 to 114) were strong (r = 0.65 and r = 0.73). Blood binding affects the disposition of tacrolimus, and plasma concentrations are indirectly and inversely related to red cell binding. The oral dose data for tacrolimus yielded a brief absorption lag time (tlag, 0.39 hour), a variable first-order absorption rate constant (ka, 4.5 +/- 3.0 hr-1), and consistent bioavailability (F, 25% +/- 10%). The area under the concentration-time curve versus 12-hour minimum concentration relationships for both whole blood and plasma were nearly linear, confirming the utility of trough values for monitoring drug exposure.

CONCLUSION

This study provides pharmacokinetic guidelines for the use of tacrolimus in patients undergoing hepatic transplantation. Nonlinear blood binding is a major source of interpatient variation in the disposition of tacrolimus.

Inhibition of phytohaemagglutinin-induced lymphocyte proliferation by immunosuppressive drugs: use of whole blood culture

A whole blood lymphocyte proliferation assay was compared to a standard method requiring the isolation of lymphocytes from blood. Both methods were used to measure inhibition of proliferative responses of phytohaemagglutinin (PHA1)-stimulated human peripheral blood lymphocytes by tacrolimus (FK 506(1)), cyclosporine A (CsA1), rapamycin (RA1), dexamethasone (DEX1), prednisolone (PR1), and methylprednisolone (MP1). Three of the drugs studied (FK 506, CsA, and DEX) yielded similar IC50 values with both methods. The whole blood proliferation assay produced modestly lower IC50 values for RA, PR and MP. The whole blood lymphocyte proliferation method is simple and can be used when only limited volumes of blood can be obtained or isolation of cells gives unsatisfactory yields.

Pharmacokinetic and pharmacodynamic effects of coadministration of methylprednisolone and tacrolimus in rabbits

Tacrolimus (FK 506) is used for treatment of various organ transplantations in combination with corticosteroids. Rabbits are a good animal model for pharmacokinetic studies of these drugs. The i.v. administration of methylprednisolone (MP; 1.25 mg/kg) (sodium succinate) at 0.5 hr after tacrolimus (0.15 mg/kg) did not influence the disposition of these drugs in rabbits. Clearances of MP were 0.45 liters/hr/kg after given alone and 0.48 liter/hr/kg after tracrolimus. The plasma and whole blood clearances of tacrolimus were 2.18 and 0.21 and 2.35 and 0.19 liters/hr/kg after separate and joint administration with the steroid. The concentrations of corticosterone were variable in all groups and was not useful as a pharmacodynamic parameter. Whole blood histamine concentrations as a marker for basophils did not change after drug administration, but increased over several weeks of experiments. Helper-T cells in rabbits as in humans show a circadian rhythm with an acrophase at 1:00 A.M. MP and tacrolimus decreased the number of circulating helper-T cells with IC50 values of 23 ng/ml for MP and 6.7 ng/ml for tacrolimus. After coadministration of these drugs, an interaction occurs, but the nature (additive or antagonistic) of this interaction was not clear. The IC50 of tacrolimus for in vitro inhibition of lymphocyte proliferation was 0.39 ng/ml (0.47 nM) and 1.02 ng/ml (2.73 nM) for MP. The maximum percentage of inhibition was 94.6% for tacrolimus and 64.9% for MP. The interaction between low concentrations of tacrolimus (0.1-0.3 ng/ml) and MP was additive, but mild antagonism was observed at higher concentration of tacrolimus (1 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory action of cimetidine on antipyrine metabolism

The influence of cimetidine on the activity of microsomal enzymes in vivo using the simple one-sample antipyrine test was investigated. The calculated antipyrine clearance unequivocally indicates the dose-dependent effect of cimetidine on the microsomal biotransformation of antipyrine. The IC50 of cimetidine inhibitory effect was 39.9 mg/kg. The duration of the effect was approximately 12 h and the lowest antipyrine clearance was observed 0.5 h following cimetidine administration. The in vivo results were confirmed by an in vitro study. Km for global metabolic processes of antipyrine in vitro was 1.3 mM. Vmax 9.1 nM/mg/min for control was decreased to 3.1 nM/mg/min after addition of cimetidine (4 mM). The inhibition constant of cimetidine determined by the method of Dixon, was 2.8 mM. Inhibition of antipyrine metabolism by cimetidine was noncompetitive.

Disposition of tacrolimus (FK 506) in rabbits. Role of red blood cell binding in hepatic clearance

Tacrolimus is a macrolide immunosuppressive drug undergoing clinical trials for organ transplantation. Whole animal studies were undertaken to assess the rabbit as an animal model for tacrolimus pharmacokinetics. The disposition of tacrolimus in rabbits following 0.5 mg/kg iv and 2.0 mg/kg po doses is similar to man. The apparent plasma clearance 1.67 liters/hr/kg is more than 5-fold higher than blood clearance 0.31 liters/hr/kg. The steady-state volume of distribution is 30.7 liters/kg for plasma and 6.3 liters/kg for whole blood. The bioavailability after oral administration calculated from plasma and whole blood is low with a mean value of 9.7%. The in vitro studies and fitting using a nonlinear red blood cell (RBC)-plasma binding/diffusion model showed slow diffusion of drug from RBC to plasma (t1/2 = 7 min, CLD = 0.085 ml/min). In perfused liver studies, the extraction ratio of tacrolimus from blood with hematocrit of 0.1 is low (0.20). However, extraction of drug from plasma is moderate (0.42), and plasma concentrations are elevated by an average of 28% because of redistribution of tacrolimus from RBC. This creates a lower apparent plasma clearance (DO/AUC) for equilibrated (30 min at 37 degrees C) samples (15.4 ml/min) compared with samples centrifuged within 5 min (22.1 ml/min). RBC efflux was accounted for using a comprehensive perfusion/diffusion model. The intrinsic metabolic clearance averaged 29.2 ml/min. Simulations showed that the apparent plasma clearance of tacrolimus is closely correlated with RBC binding capacity (whole blood:plasma ratio). Higher ratios caused greater apparent plasma clearance (lower concentration of tacrolimus in reservoir plasma) because strong binding of drug by erythrocytes prevents tacrolimus from diffusion into plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma protein binding of tacrolimus in humans

An ultracentrifugation method was used for the determination of the tacrolimus (FK 506) free fraction in plasma. Samples of 400 microL were centrifuged for 6 h at 160,000 x g, and concentrations of [3H]tacrolimus were measured in the original plasma and in the second layer of the supernatant. The binding of tacrolimus in normal plasma averaged 73% and was independent of the drug concentration. Albumin (3.5%) binding averaged 44.4-57.0%, and alpha 1-acid glycoprotein (100 mg/L) binding averaged 39%. Hepatic transplant patients exhibited 72.0% +/- 3.6% binding of tacrolimus. Plasma protein binding is probably not an important factor in the disposition of tacrolimus.

Circadian changes in the elimination of amitriptyline in rats

The circadian changes in elimination and absorption of amitriptyline after its intravenous and intragastric administration in rats were investigated. The values of such parameters as: AUC, MRT, t1/2, Cl, Vd, k(a) for amitriptyline change in the circadian rhythm. The fastest elimination of amitriptyline was observed in the dark phase (the acrophases for clearance were ca. 11 p.m. for iv administration and ca. 10 p.m. for po administration). The maximal value of clearance corresponds to the minimal values of MRT and t1/2. The acrophase for the constant absorption rate (po) falls at 7 p.m. Cyclic changes were not observed as far as the bioavailability is concerned.

Influence of ethanol on the antiarrhythmic activity of verapamil

The aim of this work was to determine the influence of ethanol on the antiarrhythmic activity of verapamil in the model of calcium arrhythmia in rats non-dependent and dependent on ethanol. The results of the experiment show that a combined, single administration of ethanol and verapamil attenuates in a statistically significant manner the antiarrhythmic effect of verapamil. Ethanol administered repeatedly together with verapamil does not diminish the antiarrhythmic activity of verapamil.

Interaction between ethanol and diltiazem in the model of barium arrhythmia in the rat

The antiarrhythmic action of diltiazem in the model of barium arrhythmia was studied in rats non-dependent and dependent on ethanol. The results of our studies showed that single intragastric administration of ethanol jointly with diltiazem did not significantly attenuate the antiarrhythmic effect of diltiazem. Ethanol administered repeatedly and jointly with diltiazem influenced the antiarrhythmic action of diltiazem in different ways, depending on the used dose of diltiazem. After repeated joint administration of ethanol and diltiazem in a lower dose, attenuation of the antiarrhythmic effect of diltiazem was not observed. Repeated joint administration of ethanol and diltiazem in a higher dose attenuated the antiarrhythmic effect of diltiazem. Those experiments also showed that single administration of diltiazem did not significantly influence the ethanol level in the blood; however, when administered repeatedly, diltiazem reduced the concentration of ethanol in blood.

The effect of some microsomal enzyme inducers on amitriptyline distribution in rats

The influence of different types of enzyme inducers: phenobarbital, Aroclor 1254 and benzo(a)pyrene, on distribution of amitriptyline and its metabolite nortriptyline in rats was investigated. The level of amitriptyline and nortriptyline in serum, brain, heart and liver was determined by gas chromatography. The maximum concentration values of amitriptyline and nortriptyline as well as areas under concentration-time curves (AUC0-6) in serum and organs were statistically compared using Student t test and AUCCOMP computer program. The results suggest that studied xenobiotics significantly influence the distribution of amitriptyline and nortriptyline in rats. The changes of these drugs concentration in target organs may be very important from the toxicological point of view.

The influence of ethanol on the distribution of amitriptyline and nortriptyline in rats

The influence of ethanol in single and multiple doses on concentration-time profile of amitriptyline (1) and nortriptyline (2) in rat serum, brain, heart, and liver was studied. AUC0-6 values were calculated and statistically compared as well as cmax values in serum and tissues. Ethanol inhibited N-demethylation of 1 and therefore 2 has not been detected in biological material. AUC0-6 and cmax values were less than in control group. All AUC0-6 and cmax values for 1 in ethanol treated groups of rats were statistically significant compared with the control group.

The interaction between ethanol and amiodarone, in the model of adrenaline arrhythmia in the rat

The antiarrhythmic activity of amiodarone was studied in the model of adrenaline-induced arrhythmia in rats non-dependent and dependent on ethanol. After single or repeated joint administration of ethanol and amiodarone the antiarrhythmic effect of amiodarone was attenuated. No significant differences in the activity of amiodarone were observed when the drug was administered in the period of abstinence.

The influence of Aroclor 1254 on the elimination of theophylline in rats

The commercial mixture of pollychlorinated biphenyls (Aroclor 1254) accelerates the elimination of theophylline (given iv and po) from the body of the rat. The increase in theophylline elimination rate by Aroclor 1254 depends on Aroclor 1254 dose and time of the dosing. Aroclor pretreatment reduced the amount of orally given theophylline in that reached the circulation by 17%. This was caused by the influence of Aroclor 1254 on the elimination rate and possible first-pass effect.

The effect of chrysene and some polycyclic aromatic hydrocarbons on the elimination of theophylline in rats

The investigations of the effect of some compounds belonging to the group of polycyclic aromatic hydrocarbons (PAH), e. g. benzo[a]pyrene, chrysene, fluorene and pyrene, on the elimination of theophylline injected i. v. into rats have shown that benzo[a]pyrene and chrysene accelerate the elimination of this drug (elimination rate constant in control group: 0.2504 h-1; after benzo[a]pyrene: 0.3626 h-1; after chrysene: 0.3582 h-1). The increase of theophylline elimination rate constant by chrysene depends on its dose, and this relationship is of sigmoid type in the dose range of 1-20 mg X kg-1. Besides, dependence of theophylline elimination rate constant on the time of chrysene dosing was also shown. After oral administration of theophylline the decrease of its amount reaching the circulation by 11% was also observed, which was caused by the influence of chrysene on the first-pass effect, beside its influence on the elimination rate.