PubMed Health⌕ Search

Biomedical subjects

J Martínková

Publications and source records attributed to J Martínková.

At least 19 recordsLinked to original sources
PubMed2006

Diurnal variation of 6beta-hydroxycortisol in cardiac patients.

The 24-hour urinary excretion of 6-beta-hydroxycortisol (6beta-OHC) and the urinary ratio of 6beta- hydroxycortisol/cortisol (6beta-OHC/UFC) have been proposed as noninvasive probes for human cytochrome P450 3A4 isoform (CYP3A4). In this study, we evaluated within- and between-day variability of 6beta-OHC excretion and 6beta-OHC/UFC ratio in nine Caucasian men with cardiac disease. Each study participant was asked to collect 24-hour urine specimens during four consecutive days in five standardized time intervals. Concentrations of UFC and 6beta-OHC were determined by immunoassay and the high-performance liquid chromatographic (HPLC) method, respectively. The HPLC method was accurate and precise, as indicated by the recovery rate of 96.5-103.3 % and less than 5.2 % and 6.3 % of the coefficient of variation for within-run and between-run assay, respectively. In patients, diurnal variations in UFC and 6beta-OHC excretion were parallel. Consequently, 6beta-OHC/UFC ratio remained stable during the day. Both, 6beta-OHC excretion and 6beta-OHC/UFC ratio showed significant relationship between 24-hour value and values measured in corresponding collection periods with best correlations obtained from night interval (22.00-06.00, r = 0.86-0.91). These results indicated that urinary 6beta-OHC excretion and 6beta-OHC/UFC ratio measured in overnight/morning urine could precisely reflect 24-hour values even in severely ill patients. In addition, a simple and sensitive HPLC method was described for determination of 6beta-OHC in urine.

Adult↗
PubMed2004

Expression of MRP2 and MDR1 transporters and other hepatic markers in rat and human liver and in WRL 68 cell line.

Here we describe a comparative study of phenotypic properties of hepatic cells in situ and in vitro. We analyzed the expression levels and distribution patterns of ABC transporters MRP2 and MDR1, pan-cytokeratin, cytokeratin 18, albumin, alpha-fetoprotein and the specific hepatocyte marker OCH1E5 in the fetal and adult rat as well as human liver tissue and in human fetal hepatocytes of WRL 68 cell line using peroxidase immunohistochemistry or immunofluorescence. Transporters MRP2 and MDR1 were expressed in all examined liver tissues, except rat ED13 embryo. The immunopositivity of these proteins was localized to the canalicular membrane of differentiating and mature hepatocytes but in the later developmental stages and in the adult liver tissues it was also found in the apical membrane of cholangiocytes. In WRL 68 cells, MRP2 and MDR1 immunoreactivity appeared after 5-6 days of cultivation and both transporters were fully expressed in the plasmalemma and in the cytoplasm 9 days after the passage. In conclusion, we observed only moderate variances reflecting diverse ontogenetic phases between the fetal and adult liver tissue. To study functions of hepatocytes in vitro, WRL 68 cells have to differentiate prior to the examination. Our findings indicate that WRL 68 cells can undergo differentiation in vitro and their antigenic profile closely resembles hepatocytes in the human liver.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

No effect of phenobarbital pretreatment of rats on methotrexate pharmacokinetics in the isolated liver perfused in a single-pass way.

Pretreatment of the rat with phenobarbital (PB) is known to increase gene expression of the canalicular multispecific organic anion transporter (cMOAT) and hepatobiliary transport of its substrates (glutathione, sulfobromophthalein). To determine the effect of PB on the hepatobiliary transport of methotrexate (MTX, another substrate of cMOAT) and its metabolism to 7-hydroxymethotrexate (7-OHMTX) in the rat, we compared the steady-state pharmacokinetics of MTX in the isolated liver of either PB-pretreated (80 mg/day/kg bw for 4 days, i.p.) or nonpretreated rats. The livers were perfused in a single-pass way at a flow rate of 15 ml/min using a perfusate which consisted of Krebs-Henseleit buffer containing glucose, taurocholate, bovine albumin and erythrocytes. During the perfusion with 50 micromol/l MTX, the steady-state biliary clearance (1.26 +/- 0.24 ml/min) in 7 nonpretreated rats accounted for a major proportion of the hepatic clearance (1.30 +/- 0.33 ml/min), metabolism of MTX to 7- OHMTX was minor (partial metabolic clearance = 0.041 +/- 0.023 ml/min). MTX concentrations in bile surpassed those in the input perfusate by approximately 100-fold. Pretreatment of rats (n = 7) with PB did not change significantly the steady-state hepatic, biliary and partial metabolic clearances of 50 micromol/l MTX. An interesting result is a 38% increase in the hepatic vascular resistance of non-pretreated livers caused by MTX. The results suggest that in rats, pretreatment with PB has no effect on the hepatobiliary transport and hydroxylation of MTX.

Animals↗
PubMed2001

Influence of amiodarone on urinary excretion of 6beta-hydroxycortisol in humans.

The present study was undertaken to evaluate the use of cortisol 6beta-hydroxylation in defining the effect of amiodarone on cytochrome CYP3A activity. To accomplish this goal, the in vivo activity of CYP3A was estimated by measuring the 24-hour urinary excretion of 6beta-hydroxycortisol (6beta-OHC) and by calculating 24-hour ratio of 6beta-hydroxycortisol to urinary free cortisol (6beta-OHC/UFC ratio). Nine cardiac patients scheduled for amiodarone treatment were recruited to participate in this study. Urine was collected over a 24-hour period from each subject before the first amiodarone administration and during the third day of oral administration of amiodarone (200 mg four times daily as a loading dose). Three days of amiodarone treatment caused a significant decrease (p<0.05) in both the 6beta-OHC/UFC ratio and the 24-hour urinary excretion of 6beta3-OHC. These results suggest that amiodarone is an inhibitor of CYP3A activity.

Administration, Oral↗
PubMed2000

High-performance liquid chromatographic assay for the determination of 5-methyltetrahydrofolate in human plasma.

An isocratic high-performance liquid chromatographic method for the determination of 5-methyltetrahydrofolate (5-MTHF) in human plasma is described. The method involves solid-phase extraction of 5-MTHF and p-aminoacetophenon (an internal standard) using Sep-Pak C18 cartridges. Separation was achieved with an ODS column using acetonitrile and phosphate buffer supplemented with octanesulfonic acid (an ion-pairing agent). The pH of the mobile phase (2.5) was optimal with respect to the mode of detection (fluorescence). The method was validated in the range of 5-MTHF concentrations from 0.0625 micromol/l to 4.0 micromol/l. Within-day and inter-day precision expressed by the relative standard deviation was less than 8.1% and inaccuracy did not exceed 8.7%. The method is specific, accurate and sensitive enough to be used in pharmacokinetic studies for the assessment of the systemic availability of 5-MTHF after leucovorin administration to patients as a rescue after high-dose therapy with methotrexate. The limit of detection was 0.17 pmol which corresponds to a plasma concentration of 1.7 nmol/l. Thus, the assay could potentially be used for the measurement of 5-MTHF in the range of physiological concentrations in plasma (5-20 nmol/l).

Chromatography, High Pressure Liquid↗
PubMed2000

In-vivo indices of CYP2D6 activity: comparison of dextromethorphan metabolic ratios in 4-h urine and 3-h plasma.

OBJECTIVES: Dextromethorpan (DM) is widely used as a probe drug to assess in vivo the activity of the cytochrome P450 2D6 (CYP2D6). The aim of the study was to compare metabolic ratios (MRs) of DM to dextrorphan (DEX) in plasma and urine. We examined, separately in urine and plasma, the relationships between the MRs which are based on DEX and those involving the sum of DEX and a secondary metabolite hydroxymorphinan (HM). Furthermore, we compared the MRs in plasma obtained with and without hydrolysis of DEX glucuronides. METHODS: Concentrations of DM and metabolites in urine and plasma were determined by HPLC after a single oral dose of 30 mg DM hydrobromide to 101 healthy Caucasian subjects. Urine was collected over the time interval 0-4 h after the dose and plasma was obtained from 95 subjects 3 h after administration. RESULTS: Six subjects (5.9%) were of poor metaboliser (PM) phenotype (urinary DM:DEX ratio >0.3). A good correlation (r2 = 0.777, P < 0.00001) was observed between the metabolic ratios of DM:DEX in plasma and urine. There was an excellent correlation, both in plasma and urine, between the log-transformed ratios of DM:DEX and of DM to the sum of molar concentrations of DEX and HM (r2 > 0.996, P < 0.00001). Plasma samples of 89 subjects (83 EM and 6 PM) were analyzed without deconjugation of DEX glucuronide also. The correlation between the plasma ratios of DM:DEX based on unconjugated DEX and those involving glucuronide (r2 = 0.793, P < 0.00001) was comparable to that reported by other authors on urine. CONCLUSION: In healthy Caucasian subjects, the MRs of DM to DEX in plasma obtained at 3 h correlated reasonably well with those in urine collected over the time interval 0-4 h after the dose. Nevertheless, repeatability of this plasma index should be determined before its wide use can be recommended. Finally, the interindividual variation in DEX metabolism to HM (catalyzed by CYP3A) contributes only minimally to the interindividual variability of the MRs.

Adult↗
PubMed2000

Influence of CYP3A metabolizer status on the pharmacokinetics and pharmacodynamics of amiodarone.

UNLABELLED: The present work was designed to determine whether the individual differences in pharmacokinetics and pharmacodynamics of amiodarone and its N-desethyl metabolite are related to cytochrome CYP3A metabolizer status. METHODS: 12 cardiac patients with inducible ventricular tachyarrhythmias during the baseline electrophysiologic study were enrolled in this study. Urinary 24-hour excretion of 6 beta-hydroxycortisol (6 beta-OHC and the ratio of 6 beta-hydroxycortisol to urinary free cortisol (6 beta-OHC/UFC) were measured before the first amiodarone administration. Trough plasma concentrations of amiodarone and N-desethylamiodarone (N-DEA) were measured after 79 +/- 11 days (2nd period) and after 182 +/- 25 days (3rd period). Electrophysiologic effects of amiodarone therapy were established with serial electrophysiologic studies in 9 of these patients at the baseline and after 79 +/- 11 days (during the second period). RESULTS: Both the 6 beta-OHC excretion and 6 beta-OHC/UFC ratio varied approximately 6-fold between the patients. We found significant inverse correlation between the 6 beta-OHC excretion and the trough plasma concentrations of amiodarone at the time of the 3rd period (rs = -0.58, p < 0.05). Similarly, there was correlation between the 24-hour urinary 6 beta-OHC excretion and trough plasma concentrations of amiodarone during the 3rd period (rs = -0.64, p < 0.025). We were unable to detect any association between CYP3A activity and amiodarone pharmacodynamics. CONCLUSION: This study points toward important information value of CYP3A metabolizer status in the context of therapeutic drug monitoring of amiodarone.

Adult↗
PubMed2000

[Renal excretion of methotrexate in an in vivo model in minipigs].

The goal of the study was to evaluate a minipig (i.e. porcine) model as the human like model for preclinical evaluation of mechanisms involved in the renal excretion of high-dose methotrexate (HDMTX). Methotrexate is in man renaly excreted in combination of glomerular filtration and active tubular drug transport (in a proximal tubule). After intravenous MTX administration, more than 95% of the amount of delivered dose was detected in urine in the form of intact MTX. To compare glomerular filtration and other ways of renal MTX excretion, the ratio between MTX clearance and clearance of inuline (which evaluate the rate of glomerular filtration only) was calculated and analyzed. Renal clearance of MTX was higher than that of inuline (Cl/Cl = 1.50 (0.095 ml/min.kg). The results showed a significant correlation between Cl and pH of urine (r = 0.525, r = 0.7243, p < 0.001, figure 1). Similar correlations were found when comparing the results of Cl and glomerular filtration (r = 0.8589, r = 0.8939, p < 0.00001) (figure 2). Significant relationship was also evident between Cl and urine pH and GF together (simultaneously) (r = 0.8677). The renal clearance of MTX varied from 1.36 ml/min.kg (measured at pH 6.0) to 3.2 ml/min.kg (measured at pH 7.0). Finally, the results indicate a significant relationship between the renal and extrarenal clearance MTX (r = 0.7227, p < 0.0001).

Animals↗
PubMed1999

Intra-individual variability and influence of urine collection period on dextromethorphan metabolic ratios in healthy subjects.

The aim of the study was to evaluate intra-individual variability in metabolic ratios (MRs) of dextromethorphan (DM) in healthy volunteers and to compare the MRs in urine collected 0-4, 0-8 and 0-24 h post-dose. Urinary molar ratios of DM to dextrorphan (MR1) and of DM to methoxymorphinan (MR2) were obtained after a single oral 27.5 mg dose of DM hydrobromide to ten healthy male and four female Caucasians (ten extensive metabolizers (EM) and four poor metabolizers (PM) of DM) to probe activities of CYP2D6 and CYP3A, respectively. Seven EM and one PM received DM on three additional occasions within 2 months. For the seven EM, the intra-individual variability (CVw) in the MRs obtained in the three urine collections ranged from 11 to 93% (MR1) and from 8 to 77% (MR2). The mean CVw estimated separately for the 4, 8 and 24 h urines by two-way analysis of variance reached 58, 57 and 44% for the MR1 and 50, 42 and 31% for the MR2, respectively. For all 14 subjects, the log-transformed ratios (MR1) obtained in the 24 h urines were highly correlated with those in either the 8 h (rs = 0.967, P < 0.0001) or 4 h urines (rs = 0.946, P < 0.0001). Correlation between the log-transformed MR2s were weaker (24 h vs. 8 h: rs = 0.829, P < 0.0001, 24 h vs. 4 h: rs = 0.831, P < 0.0001). The MR1s in 4 h and 8 h urines were only 2 and 9% less than those in 24 h urines (median differences) and varied from 48 and 47% below to 85 and 55% above (95% -CI for the differences). However, the MR2s in the 4 h and 8 h urines were shifted towards higher values by 49 and 23% and the corresponding 95% -CI limits were: 16-164% (4 h vs. 24 h) and 30-119% (8 h vs. 24 h). In conclusion, MR1 values in the 4 h urine collection agree well with those in longer collections and their use in epidemiological studies can be recommended. The intra-individual variability of approximately 50% in the MR1 has to be taken into account in clinical studies with within-subject design. Accurate determination of the MR2 requires at least a 24 h period of urine collection.

Aryl Hydrocarbon Hydroxylases↗
PubMed1998

Pharmacokinetics of low doses of methotrexate in patients with psoriasis over the early period of treatment.

OBJECTIVE: The aim of the present study was to investigate the pharmacokinetics and pharmacodynamics of low-dose methotrexate (MTX) in the early phase (3 months) after the start of antipsoriatic therapy. METHODS: Ten male and female psoriatic patients who failed to respond to previous conventional therapy were treated with 15 mg oral MTX once per week. The pharmacokinetics in plasma and the urinary excretion of MTX and 7-hydroxymethotrexate (7-OH MTX) were investigated after doses 1, 5 and 13 (corresponding to phases I, II and III, respectively). On the same occasions, MTX accumulation in erythrocytes obtained before MTX administration was investigated. Pharmacodynamics of MTX were evaluated using the psoriasis area and severity index (PASI) score. RESULTS: There were marked intersubject differences (range of coefficients of variation 34.9-76.3%) in the area under the curve (AUC), peak concentration (Cmax) and clearance (CL) of MTX. Total CL was proportional to renal clearance (CLR) (r2 = 0.735, P < 0.0001) which accounted for 73 (19)% of the former. There was a strong linear relationship (r2 = 0.819, P < 0.0001) between CL of MTX and creatinine clearance. Within 48 h of drug administration, the urinary excretion of MTX was 46-99% of the dose, while that of 7-OH MTX was 1.5-8.6%. In 8 of 10 patients, more than 70% of the MTX dose was recovered. No intraindividual variations of MTX kinetic parameters during treatment were observed. MTX concentrations in erythrocytes reached the steady-state concentration in the range 40.7-170 nmol.l(-1) after 2 months of therapy. Pharmacodynamic measurement versus pharmacokinetics revealed a significant inverse relationship between PASI score and MTX AUC (rs = -0.912, P < 0.002) and between PASI score and erythrocytic MTX (rs = -0.988, P < 0.002). CONCLUSION: The relationship between MTX pharmacokinetics (AUC or erythrocytic MTX) and pharmacodynamics (PASI score) may exist. It is likely that the efficacy of psoriasis therapy with MTX could be improved by adjusting the dose according to plasma concentrations obtained after the first MTX administration.

Adult↗
PubMed1997

An in vitro study on methotrexate hydroxylation in rat and human liver.

Methotrexate (MTX) was investigated for possible effect on the metabolism of ethoxyresorufin, pentoxyresorufin and ethoxycoumarin, the model substrates of cytochrome P450. The investigation was carried out in liver microsomes of rats pretreated with classical inducers of cytochrome P450 as well as in microsomes of two human livers. Furthermore, we measured the conversion of MTX (100microM) to its main metabolite, 7-hydroxymethotrexate (7-OHMTX), in microsomes and cytosolic fractions of rat and human livers. The inhibition of 7-OHMTX formation by menadion (inhibitor of aldehyde oxidase) and allopurinol (inhibitor of xanthine oxidase) was studied in the cytosol of rat and human livers. In both species, MTX in the concentration range 0.5-500 microM exerted no inhibitory effect on enzymatic activities associated with cytochrome P450. Moreover, we did not observe any measurable formation of 7-OHMTX in liver microsomes. MTX was metabolized at a similar rate in the cytosol of rat and human liver. Allopurinol (100 microM) reduced the rate of MTX hydroxylation by 31.5% in the cytosol of human livers but had no effect in the rat. Menadion (100 microM) decreased the rate of 7-OHMTX formation in the cytosol of human and rat liver by 69% and 94%, respectively. Our results confirmed that MTX is oxidized by a soluble enzymatic system in both the rat and human liver. In human tissues, both aldehyde oxidase and xanthine oxidase may play an important role in the metabolism of MTX. Depression of cytochrome P450 and related enzymatic activities observed in vivo cannot be explained by a direct inhibitory action of MTX on cytochrome P450.

Animals↗
PubMed1993

The effect of metipranolol and inosine on total hepatic ischemia of rats in vivo.

A protective effect of metipranolol on renal ischemia has recently been demonstrated in our laboratory. The aim of present work was to investigate the effect of this drug on a model of total hepatic ischemia. Inosine was chosen as a comparative agent. Metipranolol (1 mg.kg-1) or inosine (160 mg.kg-1) were given i.v. to rats 15 min prior to inducing of 30-min lasting hepatic ischemia. The animals were followed up for 90 min after the end of ischemia. Pretreatment with inosine almost removed the harmful effect of ischemia on bile flow. Pretreatment with metipranolol slightly minimized the post-ischemic bile flow fall, this effect having been statistically significant only at 30. min of postischemic period. Neither inosine, nor metipranolol administration influenced significantly the ALT or AST plasma activity 90 min after release of hepatic vessels occlusion.

Animals↗
PubMed1993

A beneficial effect of metipranolol pretreatment on rat kidney ischemia in vivo.

D,L-propranolol protects kidney against warm ischemia. On the contrary beta-blockers without membrane stabilizing activity (timolol, L-propranolol) do not possess this protective ability. The aim of the present work was to test the potential anti-ischemic properties of metipranolol, another beta-blocker with membrane stabilizing component. Metipranolol (1 mg/kg) was given 30 min prior to inducing the ischemia of left rat kidney followed with a contralateral nephrectomy. This pretreatment lowered the creatinemia as measured 24 hr after 60 min ischemia and improved the survival of rats after 90 min renal ischemia. The results are compatible with the concept that the membrane stabilizing activity may play a crucial role in the protective action of beta-blockers.

Animals↗
PubMed1993

Influence of temperature on the quality of hypothermic preservation of isolated rat livers.

The function normothermally perfused isolated liver will be determined in our future experiments for the assessment of the quality of previous hypothermic preservation performed by means of various preservation solutions. As the opinions on the optimal storage temperature of organs differ, the aim of the present work was to find a proper storage temperature which would be suitable for our experiments. A comparison of liver preservation using simplified UW solution (UWs) at various temperatures was performed. During the isolation the liver was flushed by 50 ml of UWs through the portal vein and stored for 24 h either at 0 degree or 10 degrees C. The isolated liver was then perfused in a recirculation manner at 37 degrees C. The livers that were stored at 0 degree C showed only mild injury resulting in a slower bile flow rate in comparison with the control group without preservation; the results were only marginally significantly different. The livers that were stored at 10 degrees C showed more pronounced injury (higher portal resistance, higher ALT and AST activity in perfusate, higher water content in livers and slower bile flow) in comparison with other groups. Storage temperature of 0 degree C seems to be more convenient for our future experiments.

Adenosine↗
PubMed1992

A contribution to the model of biliary infection in rats.

The model of biliary tract infection induced in rats given suspension of E. coli into the bile duct is described. To prevent leakage of microorganisms after the administration, a temporary ligation of the bile duct followed. Contemporary groups of sham-operated and control rats (given saline by intrabiliary injection) were compared to assess the significance of the changes. The effect of biliary infection was concentration dependent. If 0.1 ml of the concentration containing 10(2), 10(3) and 10(6) colony-forming units/ml was injected, the mortality of rats reached 8%, 57% and 65%, respectively within 24 h. Blood and bile cultures from all dead animals grew E. coli. To evaluate the effect of chronic biliary infection, the concentration of 10(2) colony-forming units/ml was used. Serum concentrations of total and conjugated bilirubin, cholesterol and creatinine, activities of S-alanine-aminotransferase, S-aspartate-aminotransferase, alkaline phosphatase, the count of leucocytes in blood, total body weight with weight of the liver were investigated on days 1, 4 and 12 after the treatment. The results showed: an increase in leucocytes (21 +/- 4.2 10(9)/l, p less than 0.02 vs control animals) on day 4, an augmentation of serum cholesterol on day 1, (2.1 +/- 0.9 mmol/l, p less than 0.02 vs control animals), the presence of E. coli in blood on day 1 and its persistence in the bile on days 1, 4 and 12. Except the bile, all of the other symptoms were reversible by day 12.

Animals↗
PubMed1992

[Chronopharmacokinetics of digoxin in compensated cardiac patients].

The authors provided evidence that the pharmacokinetics of digoxin are influenced by daily rhythms. Using doses of 0.125 mg digoxin by the oral route, after 12 hours they found a statistically higher serum digoxin concentration in the minimum before administration of the morning dose and in the maximum concentration after this dose, as compared with the minimal and maximal concentration before and after administration of the same dose in the evening. The other pharmacokinetic parameters--the area beneath the curve of serum concentrations, the time before the maximum concentration was attained and the total plasma clearance of digoxin did not differ. This chrono-pharmacokinetic relationship in compensated cardiac patients was comparable with data in the literature pertaining to healthy volunteers. To conclude it may be said that on administration of major does in the morning there is a greater risk of serum concentrations beyond the therapeutic range than during the administration of the same amount of digoxin in the evening.

Aged↗
PubMed1992

[Kinetics of gentamycin in premature infants with a low birth weight during the first four days of postnatal life].

The authors investigated in a group of 19 premature neonates with a low birthweight (0.65-2.1 kg) during the first four days of postnatal life the pharmacokinetics of gentamycin after indicated administration of 2 mg/kg of the antibiotic by the i.v. route by a 30-minute infusion in 18-hour intervals. Serum concentrations of gentamycin were assessed by immunoassay 0.5 hours before administration and then 0.5, 5.5, 11.5 and 17.5 hours after the 5th infusion, i.e. in a steady state. The maximum serum concentrations detected 0.5 hours after the completed infusion exceeded 10 mg/l in 21% of the neonates, while the minimal concentrations of the antibiotic before the next administration were above 2 mg/l in 42% of the infants. The calculation of pharmacokinetic parameters according to the one-compartment model revealed considerable interindividual differences of all values. The authors consider particularly important the low clearance value of the antibiotic (30.24 +/- 14.55 ml/kg.hour-1) which may lead to cumulation of gentamycin and its toxic action. Gentamycin administration to premature neonates should be associated with monitoring of serum concentrations of the drug which would make individual adjustment of the dosage possible.

Birth Weight↗