大鼠原位肠肝血管灌流模型的优化及完善

目的:对大鼠原位肠肝血管灌流模型的灌流液组成成分进行优化,以获取最佳灌流液配方。方法:对灌流条件进行优化,分别对Krebs-Rin-ger(K-R)液加牛血清白蛋白和甘露醇、K-R液加牛血清白蛋白和右旋糖酐T-40二者进行对比,找出最佳的灌流介质。然后对最佳的灌流介质中牛血清白蛋白的含量进行了优化。结果:K-R液加牛血清白蛋白和右旋糖酐T-40组优于K-R液加牛血清白蛋白和甘露醇组;5%牛血清白蛋白的灌流液是一个较为经济理想的灌流液。结论:在灌流介质中5%牛血清白蛋白是一个较为理想和经济的比例。     

2-苯甲酰肼叉-1,3-二噻茂烷在大鼠原位灌流肝中的代谢动力学

采用反相高压液相色谱的三内标三波长切换技术对不同剂量的农药2-苯甲酰肼叉-1.3二噻茂烷在大鼠原位灌流肝中的代谢动力学进行了研究.结果表明,该农药经门静脉进入大鼠原位灌流肝后,很快分布于肝脏中,而在灌流肝中的消除过程较缓慢。随着给药剂量的增加,大鼠肝灌流液中各种代谢产物的生成量也逐渐增加,尤以肼叉1.3-二噻茂烷和苯甲酸生成量的增加更为显著.可见,该农药在大鼠原位灌流肝中的主要代谢途径为水解作用。     

Comparison of benzo(a)pyrene metabolism in isolated perfused rat lung and liver

The metabolism of 1 mM benzo(a)pyrene was studied in isolated perfused lung and liver of 5,6-benzoflavone-pretreated rats. Benzo(a)pyrene metabolism by the liver was more rapid than by the lung, but total metabolite formation in the lung at the end of a 120-min perfusion period was comparable to that in the liver. Lung perfusate was characterized by high concentrations of free metabolites, with diols outweighing phenols; in liver perfusate free metabolite concentrations were low, and large quantities of metabolites were found as conjugates in the bile at the end of perfusion. The tissue concentrations of free diols and phenols including the precursors of the main DNA-binding secondary metabolites were higher in the lung than in the liver. These findings explain the similar level of covalent binding in perfused lung and liver previously described (Klaus et al. 1982).Abbreviations Used BP benzo(a)pyrene - 9,10-diol 9,10-dihydro9,10-dihydroxy-benzo(a)pyrene - 4,5-diol 4,5-dihydro-4,5-dihydroxy-benzo(a)pyrene - 7,8-diol 7,8-dihydro-7,8-dihydroxy-benzo(a)pyrene - 9-OH 9-hydroxy-benzo(a)pyrene - 3-OH 3-hydroxybenzo(a)pyrene - tetrols 7,8,9,10-tetrahydro-7,8,9,10-tetrahydroxy-benzo(a)pyrenes - BF 5,6-benzoflavone - TLC thin-layer chromatography - HPLC high-pressure liquid chromatography     

Effects of hypoxia/reperfusion injury on drug disposition in the rat isolated perfused liver

1. Ischaemia-reperfusion injury is known to be associated with a range of functional and structural alterations in the liver. However, the effect of this injury on drug disposition is not well understood. The present study was designed to examine the effects of hypoxia/reperfusion on the disposition of glutamate and propranolol in the rat isolated perfused liver. Both glutamate and propranolol are mainly metabolised in the pericentral region of the liver. 2. Hypoxia/reperfusion was established using the slow flow-reflow method of perfusion in both anterograde and retrograde perfusion. Glutamate metabolism was measured by the recovery of [(14)C]-glutamic acid and [(14)C]-labelled metabolites in a single pass in both anterograde and retrograde perfusion in the presence of a steady state concentration of unlabelled glutamic acid. Propranolol disposition, mean transit time and normalized variance were assessed from the outflow concentration-time profile of unchanged [(3)H]-propranolol determined after a bolus injection of [(3)H]-propranolol using HPLC and liquid scintillation counting. 3. Hypoxia/reperfusion of livers did not affect oxygen consumption, but caused significant changes in enzyme release, lignocaine hepatic availability and bile flow. 4. Hypoxia/reperfusion did not affect the hepatic metabolism of glutamate to carbon dioxide or the hepatic extraction of propranolol. Small but significant changes were evident in the distribution parameters of mean transit time and vascular disposition for the hypoxic-ischaemic liver. 5. It is concluded that reperfusion injury induced by slow flow-reflow perfusion did not influence the extraction of glutamate or propranolol, but may have affected pericentral morphology and solute distribution.     

Absence of interaction between erythromycin and a single dose of clozapine

Objective: To study the suggested pharmacokinetic interaction between erythromycin, a strong inhibitor of CYP3A4, and clozapine. Methods: Twelve healthy male volunteers received a single dose of 12.5 mg of clozapine alone or in combination with a daily dose of 1500 mg erythromycin in a randomised crossover study. Clozapine and its metabolites clozapine-N-oxide and desmethyl-clozapine were measured in serum samples which were collected during a 48 h period and in a sample of the urine secreted over the interval 0–12 h. Results: There were no significant differences in mean area under the serum concentration time curves (1348 (633) nmol h · 1⁻¹ in the control phase and 1180 (659) nmol h · 1⁻¹ in the erythromycin phase), terminal half-lives (19 (13) h and 15 (6) h, respectively), peak serum concentrations (92 (53) nmol · 1⁻¹ and 77 (40) nmol · 1⁻¹, respectively), time to peak serum concentrations (1.4 (0.7) h and 1.5 (1.0) h, respectively) or apparent oral clearances of clozapine (34 (15) l · h⁻¹ and 46 (37) l · h⁻¹, respectively). There were no significant differences in partial metabolic clearances to clozapine-N-oxide (5.1 (3.6) l · h⁻¹ and 7.8 (9.4) l · h⁻¹, respectively) or to desmethyl-clozapine (1.5 (1.3) l · h⁻¹ and 1.8 (1.7) l · h⁻¹, respectively) or in renal clearances of clozapine (0.8 (0.5) l · h⁻¹ and 1.0 (0.7) l · h⁻¹, respectively) between the two phases. Conclusion: These results demonstrate that erythromycin at a clinically relevant dosage does not inhibit the metabolism of clozapine. Hence, CYP3A4 seems to be of minor importance in the disposition of clozapine in humans at least when clozapine is taken at a low single dose. Received: 26 August 1998 / Accepted in revised form: 8 January 1999     

The interaction of rifamycin SV with hepatic transport of taurocholic acid in the isolated perfused rat liver

Summary The effect of rifamycin SV on hepatic transport of taurocholic acid was investigated using isolated perfused rat liver technique. In all experiments, the perfused liver was maintained at taurocholic acid steady state by infusing constant amount of taurocholic acid.Infusion of rifamycin SV at various rates decreased biliary secretion of bile acids in a dose-dependent manner. Replacement of rifamycin SV by perfusion medium reversed this effect.To determine the site of action of rifamycin SV, kinetic experiments with ¹⁴C-taurocholic acid were undertaken. Rifamycin SV elevated the half-life of the medium disappearance of ¹⁴C-taurocholic acid. Furthermore, the antibiotic delayed the biliary appearance of ¹⁴C-taurocholic acid.The analysis of the results gave indications that the antibiotic interferred with hepatic uptake as well as biliary secretion of taurocholic acid.Part of this publication was presented in the 18. Frühjahrstagung der Deutschen Pharmakologischen Gesellschaft (1977)     

The effect of three H2 receptor antagonists on the disposition of cyclosporin a in the in situ perfused rat liver model

The in situ, perfused rat liver model was used to investigate the effect of three H₂ receptor antagonists on the disposition of cyclosporin A (CyA) and the major human metabolite, AM1. Perfusion experiments, using standard techniques, were carried out on four groups (one control and three H₂-receptor antagonist-treated groups) of male Sprague-Dawley rats (300–350 g). All animals received CyA, 2.5 mg; the three treated groups received cimetidine (8 mg), ranitidine (3 mg), or famotidine (0.4 mg). Perfusated and bile samples were collected and assayed for CyA, AM1, and the H₂ receptor antagonists by HPLC. Results indicated that CyA perfusate concentrations in the controls and cimetidine and ranitidine-treated groups were not significantly different, although levels in the famotidine group were significantly higher at all times (p<0.05), except 30 min, compared to the controls. However, examination of the AM1 perfusate and bile data and the apparent metabolic clearance data indicated that CyA metabolism was still occurring, despite the presence of the H₂ receptor antagonist. It is suggested that the absence of a interaction may be attributed to a lack of specificity of the H₂ receptor antagonists for CYP3A, the isoenzyme responsible for CyA metabolism.     

Application of the axial dispersion model of hepatic drug elimination to the kinetics of diazepam in the isolated perfused rat liver

The application of the axial dispersion model to diazepam hepatic elimination was evaluated using data obtained for several conditions using the single-pass isolated perfused rat liver preparation. The influence of alterations in the fraction unbound in perfusate (fu) and perfusate flow (Q) on the availability (F) of diazepam was studied under steady conditions (n=4 in each case). Changes in fu were produced by altering the concentration of human serum albumin (HSA) in the perfusion medium while maintaining diazepam concentration at 1 mg L^–1. In the absence of protein (fu = 1), diazepam availability was 0.011 ±0.005 (¯x±SD). >As fu decreased, availability progressively increased and at a HSA concentration of 2% (g/100 ml), whenfu was 0.023, diazepam availability was 0.851 ±0.011. Application of the axial dispersion model to the relationship betweenfu andF provided estimates for the dispersion numbe (D _N) of 0.337±0.197, and intrinsic clearance (CL _int) of 132±34 ml min^–1. The availability of diazepam during perfusion with protein-free media was also studied at three different flow rates (15, 22.5, and 30 ml min^–1). Diazepam availability always progressively increased as perfusate flow increased, with the axial dispersion model yielding estimates forD _N of 0.393 ± 0.128 andCL _int of 144 ±38 ml min^–1. The transient form of the two-compartment dispersion model was also applied to the output concentration versus time profile of diazepam after bolus input of a radiolabeled tracer into the hepatic portal vein (n=4), providingD _N andCL _int estimates of 0.251 ±0.093 and 135±59 ml min^–1, respectively. Hence, all methods provided similar estimates forD _N andCL _int. Furthermore, the magnitude of D_Nis similar to that determined for noneliminated substances such as erythrocytes, albumin, sucrose, and water. These findings suggest that the dispersion of diazepam in the perfused rat liver is determined primarily by the architecture of the hepatic microvasculature.This work was supported by the Commission of the European Communities and the Medical Research Council. One of us (A.M.E.) was partially supported by a Merck, Sharp & Dohme Fellowship. We are grateful to Roche (Switzerland) for the supply of diazepam and 2-[¹⁴C]-diazepam, and Kabi AB (Sweden) for the supply of human serum albumin.     

Pharmacokinetics of the enantiomers of hexobarbital studied in the same intact rat and in the same isolated perfused rat liver

The pharmacokinetics of (+)- and (?)-hexobarbital were studied in the same intact rat after i.v. administration, as well as in the same isolated rat liver. The blood half-life of (+)-hexobarbital was 2–3 times shorter than than of (?)-hexobarbital, both in vivo and in vitro. No differences in apparent volume of distribution were observed, but the metabolic clearance of (+)-hexobarbital was 2–3 times greater. Clearance values in vivo were found to be equal to those in vitro for the same compound. No differences in binding to 3% albumin were observed at 3 physiological concentrations, determined by equilibrium dialysis. The animals slept much longer after injection of (+)-hexobarbital and the blood concentration at the moment of awakening was approximately 4 times lower than after injection of (?)-hexobarbital. It is suggested that a difference in anesthetic potency between the hexobarbital enantiomers at the CNS level is likely to exist.     

建立大鼠原位肠-肝灌流模型评价绿原酸的代谢

目的：建立大鼠原位肠-肝灌流模型，运用该模型研究绿原酸在大鼠肠、肝中的代谢转化。方法：采用液相色谱质谱联用（HPLC-MS）法测定大鼠原位肠-肝灌流模型灌流液中绿原酸及其代谢产物咖啡酸、阿魏酸和马尿酸。结果：绿原酸十二指肠给药后，灌流液中主要活性代谢产物为阿魏酸，同时在灌流液中也检测到少量活性代谢产物咖啡酸和大量代谢终产物马尿酸。结论：大鼠原位肠-肝灌流模型适用于绿原酸生物转化和代谢动力学的研究；绿原酸在肠中存在广泛的代谢。     

Simulation of trichloroacetic acid kinetics in the isolated perfused rat liver using a biologically based kinetic model.

Trichloroacetic acid (TCA) is a contaminant of drinking water. It induces peroxisome proliferation in livers of rats and mice and is hepatocarcinogenic in the latter species. Previous experimental studies of the kinetics of TCA in the isolated perfused rat liver (IPRL) at two doses have been reported. To gain more insight into the mechanistic processes controlling TCA kinetics in the liver a biologically based kinetic (BBK) model for the IPRL was used to analyze the experimental data. The IPRL was exposed to 25, 250, or 1000 microM TCA for 2 h in a recirculating perfusion system. These doses were not cytotoxic. The BBK model simulated the TCA concentration in perfusion medium and liver, and the biliary excretion of TCA. Separate protein binding studies showed that over 90% of TCA was bound to albumin in the perfusion medium whereas binding in liver homogenate was much lower. Integrating the information on protein binding into the BBK model, the hepatic uptake of TCA and its biliary excretion could be fitted assuming asymmetrical saturable transport at the sinusoidal membrane and linear transport at the bile canalicular membrane. To validate the BBK model, additional washout experiments were conducted in which the perfusion medium was replaced with TCA-free medium after 30 min of exposure of the liver to 1000 microM TCA. This approach illustrates the usefulness of BBK modeling for analyzing experimental kinetic data and gaining insight in kinetic mechanisms controlling the behavior of a chemical in the liver.     

离体大鼠肾脏灌流技术在发现和评价促尿酸排泄药物中的初步应用

目的为建立发现和评价促尿酸排泄药物作用的离体模型,采用离体大鼠肾脏灌流技术,观察尿酸在离体肾脏中排泄特点和丙磺舒对尿酸排泄影响。方法制备离体大鼠肾脏灌流模型,随机分为对照组和丙磺舒处理组,以含复方氨基酸和65g.L-1牛血清白蛋白的K-H灌流液循环灌流90min,定时收集导尿管流出液和灌流液,测定其中菊粉、钠、葡萄糖及尿酸含量,计算肾功能参数和尿酸排泄情况。结果离体灌流肾脏的肾小球滤过率,尿量,肾小管重吸收水、钠、葡萄糖百分率等肾功能参数在灌流的90min期间处于稳定的生理范围内;对照组灌流肾脏尿酸排泄分数、尿酸清除率及90min内总尿酸排泄量分别为30%、0.30ml.L-1和15μmol,与对照组比较,丙磺舒使离体肾脏尿酸排泄分别提高36%、54%和99%。结论离体大鼠肾脏灌流技术可用于发现和评价促尿酸排泄药物作用。     

Transformation and action of extracellular NAD+ in perfused rat and mouse livers

Aim:

Transformation and possible metabolic effects of extracellular NAD⁺ were investigated in the livers of mice (Mus musculus; Swiss strain) and rats (Rattus novergicus; Holtzman and Wistar strains).

Methods:

The livers were perfused in an open system using oxygen-saturated Krebs/Henseleit-bicarbonate buffer (pH 7.4) as the perfusion fluid. The transformation of NAD⁺ was monitored using high-performance liquid chromatography.

Results:

In the mouse liver, the single-pass metabolism of 100 μmol/L NAD⁺ was almost complete; ADP-ribose and nicotinamide were the main products in the outflowing perfusate. In the livers of both Holtzman and Wistar rats, the main transformation products were ADP-ribose, uric acid and nicotinamide; significant amounts of inosine and AMP were also identified. On a weight basis, the transformation of NAD⁺ was more efficient in the mouse liver. In the rat liver, 100 μmol/L NAD⁺ transiently inhibited gluconeogenesis and oxygen uptake. Inhibition was followed by a transient stimulation. Inhibition was more pronounced in the Wistar strain and stimulation was more pronounced in the Holtzman strain. In the mouse liver, no clear effects on gluconeogenesis and oxygen uptake were found even at 500 μmol/L NAD⁺.

Conclusion:

It can be concluded that the functions of extracellular NAD⁺ are species-dependent and that observations in one species are strictly valid for that species. Interspecies extrapolations should thus be made very carefully. Actually, even variants of the same species can demonstrate considerably different responses.     

A disposition kinetic study of tramadol in rat perfused liver

A recirculated perfusion system was used to investigate the metabolism of tramadol, an analgesic agent, in the isolated perfused rat liver. Tramadol was added to the perfusion medium at a concentration of 300 ng/ml, and the perfusate samples were collected for 180 min. The concentration of tramadol and its three main metabolites O-desmethyltramadol (M1) and N-desmethyltramadol (M2) and N,O-didesmethyltramadol (M5) were determined in perfusate samples by a rapid HPLC method. All through the study, the phase I metabolism of tramadol led to the formation of M1 metabolite from early sampling points while M5 metabolite was detectable after 50 min in 6 out of 10 perfused livers and the M2 metabolite was not detectable in any experiment. The kinetic parameters of tramadol and two detectable metabolites (M1 and M5) were then calculated in perfusate samples. The tramadol concentration decreased from 297.8 to 159.6 ng/ml, with a mean half-life of 232.4 min and a hepatic clearance of 0.73 ml/min. After 180 min, the mean concentration of M1 reached 59.5 ng/ml, resulting in a metabolic ratio of 16%, while the formation of M5 metabolite continued to a mean concentration of 14.6 ng/ml resulting in a metabolic ratio of 2% using AUC((0-180min)).     

Effect of cadmium on bromosulfophthalein kinetics in the isolated perfused rat liver system.

Bromosulfophthalein (BSP) is a relatively nontoxic organic anion used as an in vivo indicator of liver performance. Elimination of BSP via the biliary system following iv injection requires dissociation from albumin in plasma, translocation across the sinusoidal membrane, conjugation with glutathione within the hepatocyte, translocation across the bile canalicular membrane, and excretion in bile. The effects of cadmium (Cd), anin vivo hepatotoxicant in rats, on BSP kinetics in the isolated perfused rat liver (IPRL) were studied to investigate the interaction between liver toxicity and BSP kinetics. Livers were isolated from male Fisher 344 rats. After a 30-min period for acclimation to the IPRL system, livers were dosed with Cd (as cadmium acetate), in the presence of 0.25% bovine serum albumin, to give initial concentrations of 10 and 100 microM. Sixty min after Cd dosing, the IPRL system was dosed with BSP to give an initial concentration of 150 microM and the elimination kinetics of BSP from the perfusion medium were monitored. Cadmium concentrations in livers at the end of the experiments were 60 +/- 4 and 680 +/- 210 micro mol/kg for the 10 and 100 microM doses, respectively. Exposure to 10 microM Cd for 60 min resulted in a reduction in bile flow, no significant effect on lactate dehydrogenase (LDH) leakage, and slight effects on BSP clearance. Similar studies following exposure to 100 microM Cd showed a dramatic decrease in bile flow with complete cholestasis 60 min after Cd addition. LDH leakage into perfusion medium at the end of the experiment was less than 10%, indicating that Cd affected bile production well before the liver showed significant signs of necrosis. Clearance of BSP from the perfusion medium was dramatically reduced. Taken together, the data indicate that Cd has a significant effect on the kinetics of BSP in the IPRL and the dominant effects were mediated through the cholestatic effect of Cd.     

Inhibition of epoxidation of carbamazepine by valproic acid in the isolated perfused rat liver

The effect of valproic acid on carbamazepine epoxidation in the perfused liver was investigated in two separate studies. In study I, significant decreases were observed both in the intrinsic clearance of carbamazepine and the intrinsic formation clearance of carbamazepineepoxide in the presence of therapeutic concentrations of valproate. The same inhibitory effect of valproate was also observed in liver preparations from a group of animals pretreated with carbamazepine. Study II focused on the effect of valproate and carbamazepine on the apparent Michaelis-Menten parameters (V _max,m,K_m,m)associated with the intrinsic formation clearance of carbamazepineepoxide in the perfused liver. Valproate had no statistically significant effect on either the V _max,morthe K_m,m of epoxidation, although the K_m,m value was 43% higher in the presence of valproate. However, the ratio of V _max,m and K_m,m (intrinsic formation clearance) was significantly reduced by valproate. The V _max,m and K_m,m values obtained in study II predicted a significant decrease in the intrinsic formation clearance of carbamazepineepoxide, consistent with the results of study I. Carbamazepine pretreatment was associated with significant increases in apparent V _max,m and K_m,m of epoxide formation. This work was supported in part by NINCDS research grant NS-04053 and NIGMS research grant l P01 GM32165-01.     

Metabolism of 14C-2',3'-dideoxyinosine by the in situ perfused rat liver preparation

The metabolism and biliary excretion of 14C-dideoxyinosine (14C-ddI) has been investigated using the in situ perfused rat liver (PRL) preparation. After 2 h of perfusion through the liver, approximately 70-75 per cent of the total 14C-radiolabel was recovered in the perfusion medium, less than 1 per cent was excreted in bile and 15-18 per cent was retained in the liver. Hepatic clearance of ddI was 1.5 +/- 0.1 ml min-1 and half-life for the elimination of ddI from the medium was 22.9 +/- 2.0 min (n = 3). Hepatic extraction was estimated to be 7.5 per cent. HPLC analysis of the effluent perfusate indicated that ddI was metabolized to hypoxanthine, xanthine, uric acid, and to a polar metabolite which was tentatively identified as allantoin. Approximately 60-65 per cent of the ddI dose was converted to allantoin after 2 h of perfusion. Of the other three metabolites, uric acid levels increased to 20-30 per cent of the dose after 45 min and declined to about 5 per cent of the dose by the end of the perfusion period. Levels of hypoxanthine and xanthine were low and both compounds were not detected in the perfusate after 45 min post-infusion. In bile, the major peak, which accounted for about 50 per cent of the 14C-radiolabel co-eluted with the putative metabolite, allantoin (0.4 per cent of the dose). Uric acid (0.06 per cent of the dose) was the only other metabolite detected in bile. These results suggest that biliary excretion is a minor pathway for the elimination of ddI. Furthermore, ddI is rapidly cleared and metabolized by the liver to hypoxanthine, xanthine, uric acid, and to allantoin.     

Alteration of fexofenadine disposition in the rat isolated perfused liver following injection of bacterial lipopolysaccharide

1. The aim of the present study was to examine the effect of bacterial lipopolysaccharide (LPS) on the disposition of an organic anion transporting polypeptide and P-glycoprotein substrate in the rat isolated perfused liver. 2. Male Sprague-Dawley rats were divided into four groups. Three of the groups received 1, 2.5 or 5 mg/kg, i.p., Escherichia coli LPS in sterile saline. The fourth group received an equivalent volume of sterile saline i.p. Twenty-four hours after treatment, rats were anaesthetized and the liver isolated and perfused with fexofenadine at an initial concentration of 2000 ng/mL in a recirculating system. Perfusate and bile samples were collected for 60 min and the liver was collected at the end of the perfusion. Fexofenadine concentrations were determined by HPLC. Fexofenadine pharmacokinetic parameters, the final liver : perfusate (L : P) and bile : liver (B : L) concentration ratios were determined. 3. Injection of LPS changed the hepatic disposition of fexofenadine. The changes were most marked in the 5 mg/kg LPS group. Notably, clearance from the perfusate (CL) and into the bile (CLB; 5.9 +/- 0.6 and 1.24 +/- 0.20 mL/min, respectively), L : P (44 +/- 11) and B : L (17 +/- 2) were all reduced (P < 0.05) in this group compared with control (CL 10.0 +/- 1.1 mL/min; CLB 2.7 +/- 0.5 mL/min; L : P 87 +/- 14; and B : L 30 +/- 4). 4. In conclusion CL and CLB were reduced following treatment with LPS in a manner consistent with downregulation of both canalicular and sinusoidal transport.     

A comparatmental model for hepatic transport of taurocholic acid in isolated perfused rat liver

Summary In order to characterize the transport of bile acids through the liver and to study the influence of drugs on these processes, a kinetic model for hepatobiliary transport of taurocholic acid (TC) using the isolated perfused liver was developed. After the system was brought to a steady state by infusing TC at a constant rate, a tracer dose of ¹⁴C-TC was injected into the medium. The medium disappearance of ¹⁴C-TC followed a first-order kinetic with a single rate constant.The plot of the biliary secretion rate of radioactivity versus time revealed a curve composed of at least three exponential components. From the described results and the present knowledge of hepatobiliary transport of bile acids we proposed a three compartment model, composed of a perfusion medium compartment and two liver compartments. Parameters calculated from the model constants agreed well with model-independent estimations.The influence of bromosulfophthalein (BSP) on the kinetic parameters was studied to compare the result with the known effect of BSP on hepatic transport of taurocholic acid. BSP decreased the constant describing the fractional transfer of taurocholic acid from medium into the liver, which is in agreement with the inhibition of hepatic uptake of taurocholic acid by BSP. Thus a three compartment model may adequately define the hepatobiliary transport of taurocholic acid in the isolated perfused rat liver.     

A comparison of EMIT and FPIA methods for the detection of cyclosporin A blood levels: does impaired liver function make a difference?

Objective: Apparent cyclosporin A (CSA) blood levels, as determined by fluorescence polarization immunoassay (FPIA) and enzyme-multiplied immunoassay technique (EMIT), were compared in CSA-treated patients with various degrees of liver dysfunction. Methods: FPIA and EMIT were performed in parallel according to test manufacturer instructions in blood from kidney (n=82), liver (n=96) and heart transplant (n=20) patients. Results: The precision of both techniques was greatest in patients with the highest blood levels, and at each blood level greater for the FPIA than for the EMIT. Apparent CSA blood levels, as determined by EMIT, were typically approximately 70% of those determined by FPIA, indicating greater cross-reaction of the antibody in the FPIA with CSA metabolites. However, the ratio of values determined with EMIT and FPIA was very similar in kidney, liver and heart transplant patients. Among liver transplant patients it was also very similar in those without major alterations of hepatic function and in those with impaired excretory (increased bilirubin and γGT) or synthetic (i.e., reduced thromboplastin time) function. Extended storage of blood samples for up to 10 days did not affect apparent CSA blood level estimates by EMIT in a clinically relevant manner. Conclusions: We conclude that the greater specificity of the antibody in the EMIT for the CSA parent compound does not translate into a clinically relevant advantage for CSA monitoring. Received: 20 September 1996 / Accepted in revised form: 17 February 1997