[Simulation of bioequivalence study on the base of dissolution curves].

A computer method based on the in vitro dissolution of drug preparations has been elaborated for the estimation of bioequivalence. The method generates a "dissolutaion surface" from the parameters of time (X-axis), from pH (Y-axis) and from the dissolved amount (A) in % of the drug. This dissolution surface allows the determination of the general dissolution curve of the test and reference preparations.

Differential inhibitory effect of cyclosporin A and bosentan on taurocholate uptake in human and rat hepatocytes as a function of culturing time.

Bile salt transport across hepatocytes requires a coordinate action of transporters, which is thought to be a target for drug-induced cholestasis. Hepatocytes provide the most competent in vitro model to predict transporter-related toxic drug effects. The aim of this study was to show a correlation between inhibitory potential of drugs and the change of rate, as well as of the active to passive ratio of taurocholate uptake in these cells.

Contribution of high basolateral bile salt efflux to the lack of hepatotoxicity in rat in response to drugs inducing cholestasis in human.

Intrahepatic bile acid accumulation due to inhibition of the bile salt export pump (BSEP) has been proposed as a mechanism for drug-induced cholestasis. Many cholestatic drugs do not initiate hepatotoxicity in rats, although they inhibit rat Bsep and cause elevated serum bile acid concentration. In this study, we examined changes in the taurocholate (TC) transport in response to cholestatic drug treatments in human and rat sandwich-cultured hepatocytes.

ABCC2/Abcc2: a multispecific transporter with dominant excretory functions.

ABCC2/Abcc2 (MRP2/Mrp2) is expressed at major physiological barriers, such as the canalicular membrane of liver cells, kidney proximal tubule epithelial cells, enterocytes of the small and large intestine, and syncytiotrophoblast of the placenta. ABCC2/Abcc2 always localizes in the apical membranes. Although ABCC2/Abcc2 transports a variety of amphiphilic anions that belong to different classes of molecules, such as endogenous compounds (e.

Biliary efflux transporters involved in the clearance of rosuvastatin in sandwich culture of primary rat hepatocytes.

Rosuvastatin (a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor) has been shown to be excreted mostly unchanged into the bile; interactions on the level of hepatic apical efflux transporters may represent a risk of liver toxicity. So far, controversial and insufficient data are available concerning transporters involved in the elimination process. This study was designed to elucidate, which transporters take part in the biliary clearance of rosuvastatin using sandwich-cultured primary rat hepatocytes.

Limited applicability of 7-methoxy-4-trifluoromethylcoumarin as a CYP2C9-selective substrate.

Fluorometric substrates selective for various cytochrome P450 isoforms (P450s) have great advantages in in vitro enzyme inhibition and induction studies because they are highly sensitive and suitable for rapid screening. 7-Methoxy-4-trifluoromethylcoumarin (MFC) has been reported as a CYP2C9-selective substrate. The present study investigated the relative catalytic selectivity of several human P450s in the O-demethylation of MFC and the applicability of MFC as a probe substrate for CYP2C9.

Interspecies differences in acetaminophen sensitivity of human, rat, and mouse primary hepatocytes.

Most of the experiments studying acetaminophen (APAP) induced hepatotoxicity were performed using moue as model specie, right because its high sensitivity. While the toxic responses can be called forth easily in mice, the human relevancy of these results is questionable. In this study human, rat, and mouse primary hepatocytes were treated with increasing concentrations of APAP, and cell viability was measured by MTT cytotoxicity assay.

Modulation of sinusoidal and canalicular elimination of bilirubin-glucuronides by rifampicin and other cholestatic drugs in a sandwich culture of rat hepatocytes.

Aim: Drug-induced hyperbilirubinemia has been shown to often be derived from modulation of the expression and activity of hepatobiliary transporters. In this study we examined the interactions of some therapeutic agents, which have been shown to cause cholestasis, with the elimination of bilirubin-glucuronides, in order to clarify whether these drugs modify the activity of Mrp2 and Mrp3 directly.

Methods: The modulation of bilirubin-glucuronide elimination with rifampicin, probenecid, indomethacin and benzbromarone was assayed in sandwich cultured rat hepatocytes.

Effect of mirtazapine on the CYP2D activity in the primary culture of rat hepatocytes.

Our previous studies carried out on rats showed that mirtazapine given intraperitoneally at a dose of 3 mg/kg, twice a day for two weeks, increased the activity of CYP2D measured as ethylmorphine O-deethylation in liver microsomes. The aim of the present work was to find out whether the mirtazapine-induced increase in the CYP2D activity observed in vivo is connected with the central action of mirtazapine or the drug acts directly on hepatocytes. For this purpose, we studied the influence of pharmacological concentrations of mirtazapine (0.

Biotransformation of deramciclane in primary hepatocytes of rat, mouse, rabbit, dog, and human.

The metabolic fate of deramciclane [(1R,2S,4R)-(-)-2-phenyl-2-(2'-dimethylamino-ethoxy)-1,7,7-trimethyl-bicyclo[2.2.1]heptane], a new anxiolytic drug candidate, has been determined in rat, mouse, rabbit, dog, and human hepatocytes.

The spectrum of enzymes involved in activation of 2-aminoanthracene varies with the metabolic system applied.

The aim of this study was to estimate the involvement of cytochrome P450s (CYPs) in the metabolic activation of 2-aminoanthracene (2AA) by use of metabolic systems such as liver S9 or hepatocytes from untreated and beta-naphthoflavone (BNF)- or phenobarbital (PB)-treated rats. Metabolic activation was determined in the Salmonella reverse mutation assay (Ames test). Unexpectedly, both enzyme inducers, BNF and PB, significantly decreased the mutagenicity of 2AA activated by S9 fractions.

[The role of drug metabolizing enzymes in the effect and side-effect of the drugs].

The authors give an overview on the role of drug metabolizing enzymes in the effect and side-effect of drugs. They describe the properties of cytochrome P450 and other phase I enzymes (hydrolases, flavin-monooxygenases), as well as of phase II. enzymes (glucuronyl-, sulfate-, glutathione-, acetyl-, methyltranferases), their polymorphism, inductive and inhibition properties.

Canalicular and sinusoidal disposition of bilirubin mono- and diglucuronides in sandwich-cultured human and rat primary hepatocytes.

Due to cholestasis or adverse drug effects, the excretion of bilirubin conjugates can decrease; therefore, the level of bilirubin (B) and bilirubin glucuronides (BGs) increases in the serum with the concomitant shift of bilirubin diversus monoglucuronide (BDG/BMG) equilibrium. The aim of this study was to utilize the collagen-sandwich culture of hepatocytes as an in vitro model for studying B conjugation and canalicular versus sinusoidal disposition of BGs. Canalicular and sinusoidal efflux of BMG and BDG obtained in sandwich-cultured rat primary hepatocytes was compared with that measured in human hepatocyte cultures.

Role of CYP2E1 in deramciclane metabolism.

The aim of our study was to identify the form(s) of cytochrome P450 responsible for the metabolism of deramciclane, a new anxiolytic drug candidate. The main routes of biotransformation in hepatic microsomes were side chain modification (N-demethylation or total side chain cleavage) and hydroxylation at several points of the molecule. Although several cytochrome P450 forms were involved in the metabolism, the role of CYP2E1 should be emphasized, since it catalyzed almost all steps.

The effect of synthetic glucocorticoid, dexamethasone on CYP1A1 inducibility in adult rat and human hepatocytes.

Glucocorticoids act synergistically with polycyclic aromatic hydrocarbons in increasing mRNA and protein levels of CYP1A1 in rat liver. The action of dexamethasone to modify CYP1A1 expression has been investigated in adult human hepatocytes. The effect of dexamethasone on the induction of CYP1A1 by 3-methylcholanthrene is different in rat and human liver cells.

Inhibition of cytochrome P450 enzymes participating in p-nitrophenol hydroxylation by drugs known as CYP2E1 inhibitors.

p-Nitrophenol hydroxylation is widely used as a probe for microsomal CYP2E1. Several drugs are known as CYP2E1 inhibitors because of their capability to inhibit p-nitrophenol hydroxylation. Our results suggest further participation of CYP2A6 and CYP2C19 enzymes in p-nitrophenol hydroxylation.

Comparative study in the Ames test of benzo[a]pyrene and 2-aminoanthracene metabolic activation using rat hepatic S9 and hepatocytes following in vivo or in vitro induction.

We studied the replacement of hepatic S9 with in vivo and in vitro induced hepatocytes as a metabolic activation system with the aim of broadening the possibilities of mutagenic assays. Rats were pretreated with beta-naphthoflavone (BNF), phenobarbital (PB), 3-methylcholanthrene (MC) and a combination of BNF and PB (BNF + PB). Mutagenic activation of benzo[a]pyrene (BP) and 2-aminoanthracene (2AA) by hepatic S9 and hepatocytes was determined in the Ames test.

In vitro induction of cytochrome P450 enzymes in hepatocytes isolated from the regenerating rat liver.

Partial hepatectomy results in the loss of cytochrome P450 enzymes. During regeneration, the levels of cytochrome P450 activities, apoproteins and mRNA are reduced. Our present study investigated CYP1A, CYP2E1 and CYP3A induction in the cells of rat liver regenerating for 1, 3, 7, or 14 days.

GYKI-47261, a new AMPA [2-amino-3-(3-hydroxymethylisoxazole-4-yl)propionic acid] antagonist, is a CYP2E1 inducer.

CYP2E1-inducing capacity of xenobiotics was determined in cultured hepatocytes on the basis of enzyme activities (chlorzoxazone 6-hydroxylation and 7-ethoxycoumarin O-dealkylation) and protein levels. Hepatocytes in culture showed rapid loss of CYP2E1 enzyme during 72 h. CYP2E1 inducers (ethanol, dimethyl sulfoxide, acetone, isopropanol, pyrazole, and imidazole) were able to prevent the fast decrease of the activities and protein levels of CYP2E1 enzyme.

A study on CYP1A inhibitory action of E-2-(4'-methoxybenzylidene)-1-benzosuberone and some related chalcones and cyclic chalcone analogues.

In vivo investigation of E-2-(4'-methoxybenzylidene)-1-benzosuberone (4a) on the 7,12-dimethylbenz[a]anthracene (DMBA)-induced onco/tumor suppressor gene expressions suggested that inhibition of metabolic activation of DMBA might play a role in the observed activity of the compound. In order to explore this possible biological action we have investigated whether 4a and some of its structurally related analogues had inhibitory effects on the CYP1A enzymes. During our study 7-ethoxyresorufin O-dealkylation activity of CYP1A isoenzymes was measured in liver microsomes prepared from 3-methylcholanthrene treated male rats.

Coordinate regulation of UDP-glucuronosyltransferase UGT1A6 induction by 3-methylcholanthrene and multidrug resistance protein MRP2 expression by dexamethasone in primary rat hepatocytes.

Concentration-dependent regulation of 3-methylcholanthrene (MC) inducibility of UDP-glucuronosyltransferase UGT1A6 by the synthetic glucocorticoid, dexamethasone (DEX) was studied. Treatment of cultured rat hepatocytes with MC, 0.1, 1, and 10 microM DEX, and MC combined with DEX, resulted in different induction patterns measured in the intact cells compared to that observed in the microsomes prepared from the same cells.

Reduction of toxic metabolite formation of acetaminophen.

Acetaminophen is a widely used over-the-counter drug that causes severe hepatic damage upon overdose. Cytochrome P450-dependent oxidation of acetaminophen results in the formation of the toxic N-acetyl-p-benzoquinone-imine (NAPQI). Inhibition of cytochrome P450 enzymes responsible for NAPQI formation might be useful--besides N-acetylcysteine treatment--in managing acetaminophen overdose.

In vitro induction of bilirubin conjugation in primary rat hepatocyte culture.

UDP-glucuronosyltransferase (UGT1A1) is a critical enzyme in the elimination of bilirubin. The aim of our study was to investigate bilirubin conjugation in primary rat hepatocyte culture and the in vitro inducibility of this isoenzyme by inducing compounds of different classes: dexamethasone, clofibrate, rifampicin, and methylcholanthrene. Hepatocytes exhibited a marked decline in UGT1A1 activity in the first 4 h of culturing (10% of initial activity) and the recovery took 72 h.