Hepatic clearance and biliary secretory rate maximum of taurocholate in the recirculating and single pass isolated perfused rat liver. Effects of the cholestatic agent, estradiol-17 beta-(beta-D-glucuronide)

The ability of the cholestatic steroid glucuronide, estradiol-17 beta-(beta-D-glucuronide) (E(2)17G), to inhibit the hepatic clearance (ClH) and biliary secretory rate maximum (SRm) of taurocholate was investigated in the recirculating and single pass isolated perfused male rat liver. In the recirculating perfused liver, E(2)17G (0, 2, 4, or 6 mumol) was added as a bolus dose to the reservoir at zero time while taurocholate was infused into the portal vein in increasing amounts (15, 30, 45, or 60 mumol/mL; 1 mL/hr for 15 min each). E(2)17G (4 mumol) caused a significant (P less than 0.05) inhibition of bile flow and bile acid secretion at 10-15 min during infusion of 15 mumol/hr taurocholate but did not inhibit the SRm which occurred at 42 min, indicating that E(2)17G had not caused an irreversible inhibition of taurocholate transport. E(2)17G (6 mumol) caused a profound and irreversible inhibition of bile flow attributable to retention of E(2)17G in the liver. The noncholestatic estradiol-3-(beta-D-glucuronide) (E(2)3G; 6 mumol) had no significant effect on bile flow or the SRm. In the single pass perfused liver (10 mL/min flow rate), E(2)17G (0, 1, 2, 5, or 10 nmol/mL) or E(2)3G (2 nmol/mL) was added to the perfusate resulting in a stable infusion to the liver. [3H]Taurocholate was infused into the portal vein in increasing amounts to give inflow concentrations (Cin) of 25, 50, 75 or 100 nmol/mL. In the absence of E(2)17G, taurocholate ClH decreased from 0.92 to 0.70 mL/min/g liver with increasing taurocholate concentrations. Neither E(2)17G nor E(2)3G altered the ClH of 25 nmol/mL taurocholate. E(2)17G (10 nmol/mL) inhibited bile flow and bile acid secretion first at 20-25 min, followed by inhibition of ClH of 75 and 100 nmol/mL taurocholate (35-60 min). In contrast, E(2)3G stimulated bile acid secretion and increased the SRm by 80%. Thus, at doses that did not block its own elimination, E(2)17G did not cause an irreversible inhibition of taurocholate transport into bile. E(2)17G did not directly inhibit the uptake of taurocholate into the liver but first inhibited the biliary excretion of taurocholate, resulting in its intrahepatic accumulation and decreased clearance from the perfusate.     

Receptor-mediated stimulation of taurocholate efflux from the rat hepatocyte and the ex vivo perfused rat liver

The peptide hormone, arginine-vasopressin[( Arg8]vasopressin, AVP), stimulates efflux of the bile salts taurocholate and glycocholate from the rat hepatocyte in suspension via its association with the V1 receptor on the hepatic cell membrane. At a concentration ratio of 5:1 (antagonist to hormone), the V1 vasopressin antagonist, (dCH2)5Tyr(Me)AVP, inhibits the vasopressin induced efflux of taurocholate by approximately 82%, and of glycocholate, by approximately 85%. In contrast, the V2 antagonist (d(CH2)5[D-Ile2,Ala4]AVP, does not interfere with the stimulation of taurocholate and glycocholate efflux by vasopressin. In the isolated perfused rat liver, vasopressin (5 X 10(-10) M) causes an immediate increase of 55 +/- 12% over baseline in [14C]taurocholate secretion and a corresponding increase in bile flow. A more gradual and prolonged increase in [14C]taurocholate secretion, reflecting an increased biliary concentration of [14C]taurocholate, is observed beginning 6 min after vasopressin, reaching a plateau of 23 +/- 12% over baseline by 14 min and returning to baseline by 30 min. The mean rate of 14C secretion during the 30 min following administration of vasopressin (non-steady state) is increased by 14.3 +/- 6.4% over pre-infusion steady-state baseline (P less than 0.05). Prior administration of the V1 receptor antagonist d(CH2)5Tyr(Me)AVP attenuates these effects of vasopressin. The combination of these in vitro and in vivo findings suggest that vasopressin may play a role in regulating bile salt efflux. Furthermore, these studies in the isolated hepatocyte and the intact liver may provide a unique approach for defining biochemical changes associated with bile salt transport from the hepatic cell.     

Zonal distribution of the cation lucigenin in rat liver: influence of taurocholate

The yellow fluorescent cation lucigenin (LU) was used as a model compound to study acinar heterogeneity in transport of hydrophilic cations that enter the liver by adsorptive endocytosis. Hepatic uptake was fast and saturable. The extraction was about 50% in a cyclically perfused rat liver preparation in which endogenous bile salts were replaced by the infusion of taurocholate (TC). Fluorescence microscopy on 8-microns liver sections revealed a striking distribution pattern. LU appeared to be concentrated in micro- and macrovesicular structures in the cell. At the same time, LU skipped the first cells of the acinus, zone 1 in an antegrade and zone 3 in a retrograde perfusion. A downstream localization of the dye was the result. Single-pass perfusions with TC concentrations ranging from 0 to 180 microM showed that hepatic clearance of LU negatively correlated with the TC concentration (p less than 0.005). Clearance fell from 1.99 +/- 0.06 ml/min-g of liver(mean +/- SD) without TC to 1.61 +/- 0.21 with 45 microM TC and 1.65 +/- 0.12 with 180 microM TC. Moreover, in the absence of TC we observed a homogeneous distribution of LU. TC induced in the acinus a nonfluorescent upstream area that expanded with increasing TC concentration. We concluded that TC inhibited uptake of LU; a high medium concentration of TC in zone 1 (antegrade) was accompanied by a low uptake of LU in this zone, resulting in a downstream increasing acinar gradient. Hepatic uptake and acinar distribution of certain cationic drugs in vivo may, therefore, vary with the variable input of bile salts in the portal circulation and, hence, with nutritional status and the time of day.     

The effect of dimetindene on liver and kidney function in the cholestatic rat

Dimetindene (active principle of Fenistil) belongs to the group of H1-antihistamines which are used in the treatment of allergic disorders. An experimental approach was made to clarify the risk of dimetindene application during the conditions of an impaired liver function as a consequence of extrahepatic cholestasis (bile-duct ligation). Acute and subchronic treatment with dimetindene (1 and 10 mg/kg p.o., respectively) did not enhance the effect of cholestasis on the parameters of liver function (plasma bile acids, glutamate pyruvate transaminase (GPT), alkaline phosphatase) or kidney function (creatinine, urea retention in plasma). It is concluded that the use of dimetindene in the treatment of pruritus during cholestasis is without notable risk.     

A novel irinotecan-lipiodol nanoemulsion for intravascular administration: pharmacokinetics and biodistribution in the normal and tumor bearing rat liver

Colorectal cancer is one of the most common cancers in the United States and treatment options are limited for patients who develop liver metastases. Several chemotherapeutic regimens have been used for transvascular liver-directed therapy in the treatment of colorectal liver metastases without clear evidence of superiority of one therapy over another. We describe the development of a novel nanoemulsion through combining irinotecan (IRI), a first line systemic agent used for the treatment of colon cancer, with lipiodol, an oily contrast medium derived from poppy seed oil, and evaluated its pharmacokinetic and biodistribution profile as a function of portal venous chemoembolization (PVCE) versus transarterial chemoembolization (TACE) delivery. The Tessari technique was used to create a stable emulsion (20 mg IRI mixed with 2 mL lipiodol) with resultant particle size ranging from 28.9 nm to 56.4 nm. Pharmacokinetic profile established through venous sampling in Buffalo rats demonstrate that the area under the curve (AUC_0−∞) of IRI was significantly less after PVCE with IRI-lipiodol as compared to IRI alone (131 vs. 316 µg*min/mL, p-value = .023), suggesting significantly higher amounts of IRI retention in the liver with the IRI-lipiodol nanoemulsion via first-pass extraction. Subseqent biodistribution studies in tumor-bearing WAG/Rjj rats revealed more IRI present in the tumor following TACE versus PVCE (29.19 ± 12.33 µg/g versus 3.42 ± 1.62; p-value = .0033) or IV (29.19 ± 12.33 µg/g versus 1.05 ± 0.47; p-value = .0035). The IRI-lipiodol nanoemulsion demonstrated an acceptable hepatotoxicity profile in all routes of administration. In conclusion, the IRI-lipiodol nanoemulsion via TACE showed promise and warrants further investigation as an option for the treatment of metastatic colorectal cancer.     

大鼠肝微粒体中葛根素的液相色谱-质谱测定法及药物代谢动力学

目的建立大鼠肝微粒体中葛根素及其代谢物的液相色谱质谱测定法,并研究葛根素在大鼠肝微粒体中的药物代谢动力学。方法色谱柱为Waters C18柱(150 mm×4.6 mm,5μm),流动相为甲醇水(体积比为50∶50),通过电喷雾电离源(ESI),以正离子方式进行检测。结果方法的回收率为95.6%~96.8%,其日内、日间的RSD分别为4.9%~7.6%和3.7%~6.2%,葛根素的质量浓度在0.5~20 mg.L-1内与峰面积呈良好的线性关系。在温孵时间0~40 min内、微粒体蛋白质量浓度在0.5~2.0 g.L-1内,葛根素呈线性消除,随着肝微粒体蛋白质量浓度的增大,葛根素呈线性消除,葛根素可被肝微粒体代谢成大豆苷元。其代谢机理为还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH)依赖性的氧化代谢。还原型烟酰胺二核苷酸(NADH)对葛根素代谢基本没有催化作用。结论葛根素在大鼠肝微粒体内被迅速代谢,大鼠肝微粒体P450酶参与了葛根素的代谢。     

Hepatic clearance measurements and pharmacokinetics.

This review emphasizes the need for well-defined models for hepatic pharmacokinetics and discusses the interpretation of hepatic clearance measurements. Such recent approaches are subjected to theoretical and experimental comparisons. The pharmacokinetic consequences, including a classification of drugs according to hepatic clearance, are outlined.     

Hepatic uptake and biliary secretion of bile acids in the perfused rat liver.

Hepatic uptake and biliary secretion have been evaluated in the isolated perfused rat liver for cholic, chenodeoxycholic, ursodeoxycholic acid, both free and taurine-conjugated; the physicochemical properties of the bile acids have also been calculated and related to these experimental parameters. Cholic acid disappearance rate from the perfusate was the fastest, followed by that of ursodeoxycholic and chenodeoxycholic; it was also faster for taurine-conjugated bile acids than for their respective unconjugated forms. The recovery in bile was higher for conjugated than for unconjugated bile acids, and among each class, was higher for cholic than for chenodeoxycholic and ursodeoxycholic. The hepatic uptake correlated negatively (r = -0.99) with the bile acid lipophilicity, while the biliary secretion correlated with the solubility of the molecules. These results show the effect of the physicochemical properties of BA on their hepatic handling, at the physiological concentration of BA in the portal blood.     

Hepatic clearance and retention of aluminium: studies in the isolated perfused rat liver

Aluminium (Al) exposure can result in Al accumulation in the liver and this metal can be toxic to the hepatic tissue at high concentrations. In the present study the model of the isolated perfused rat liver was used to investigate the hepatic handling of Al. Livers from male Wistar rats were perfused in a recirculating system for 240 min. The liver function remained unchanged at perfusate concentrations of Al ranging from 4.9 to 1530.0 μ/1. At higher Al levels of 6535.3–16 694.9 μ/1 signs of toxicity towards isolated perfused livers were observed as indicated by an increased release of the enzymes AST and ALT into the perfusate, a pronounced reduction of bile flow rate and a 50% suppression of oxygen consumption. The hepatic Al clearance was low and decreased with increasing concentrations of Al in the perfusate from 4.3 + 0.6 μ/min per g liver at a nominal Al concentration of 9.1 μ/l in control perfusate to 0.04 ± 0.02μl/min per g liver at the highest concentration group. There was almost a linear dose dependent retention of Al in the liver with 4.9–635.7 μ Al/1 perfusate while at higher concentrations Al levels in this organ increased disproportionally. It is concluded that by using the isolated perfused rat changes of liver functions occur only at very high Al concentrations in the perfusate and that only negligible amounts of Al are eliminated by the liver.     

胆汁淤积性肝病的诊断和治疗进展

胆汁淤积性肝病是临床常见的淤积综合征,属于胆汁分泌和排泄异常的器质性病变,以皮肤瘙痒、黄疸、疲劳和脂肪泻等常见的淤积症状为主要表现,缺乏特异性表现,给临床诊断和治疗带来了诸多不利。近年,有关胆汁淤积性肝病的诊断和治疗方面的研究迅速增多,临床上按照病因将其分为胆管性胆汁淤积、肝细胞性胆汁淤积和混合性胆汁淤积。由于该病的诊治受到多种因素的影响,因此在规范化基础上进行个体化治疗成为该病的主要方案。基于该病对患者身体健康的危害,本文对近5年有关胆汁淤积性肝病的诊断和治疗文献进行了总结,现将其综述如下。     

Transmigration of mitochondrial GOT in cholestatic liver injury

Cholestatic liver injury was experimentally induced in rats by administration of alpha-naphthylisothiocyanate (ANIT) and the peak activity of mitochondrial L-aspartate: 2-oxoglutarate aminotransferase (m-GOT) released in the serum was found to precede the peak of total GOT activity. To investigate the permeability of the mitochondrial inner membrane to m-GOT, liver mitochondria obtained from rats given ANIT were fractionated into two subfractions: one containing the matrix and the inner and outer membranes, and the other containing the intermembrane space, and the m-GOT in these fractions was determined. As a result, 12 hours after ANIT administration, the relative activity of GOT in the subfraction containing the matrix and the membranes was significantly lower than the control value. In the same period, the ratio of GOT activity to the activity of glutamate dehydrogenase, which is a marker enzyme for the matrix, and the ratio of GOT activity to the activity of cytochrome c oxidase, which is a marker enzyme for the inner membrane, were both decreased by half. In contrast, the relative GOT activity for the subfraction containing the intermembrane space was significantly increased 12 hours after administration. Also, the ratio of GOT activity to the activity of adenylate kinase, a marker enzyme for the intermembrane space, was doubled. These results suggest that m-GOT, which is originally located in the mitochondrial matrix, transmigrated to the intermembrane space via the inner membrane under the effect of ANIT administration.     

Uptake and localisation of haematoporphyrin derivative in normal rat liver

Fluorescence microscopy and analytical subcellular fractionation were used to investigate the hepatic localisation of haematoporphyrin derivative (HPD) after intraperitoneal administration. HPD was found to rapidly accumulate in the liver and then to slowly decline over 48 hr. Fluorescence microscopy showed that although at early times porphyrins could not be localised to a particular cell type, at 24 hr porphyrins were preferentially localised to the Kupffer cells of the liver. Subcellular fractionation studies indicated that the initial rapid uptake of HPD was to the cytosol. However, at 24 hr, porphyrins appeared to be localised to lysosomes. Lysosomal localisation was confirmed using the selective organelle perturbant, Triton WR 1339. No evidence was found either at the light microscope level or by subcellular fractionation to suggest association of HPD with other organelles. HPLC analysis showed that the porphyrins present in the plasma and in the cytosol and lysosome fractions were mainly the (RS, SR) and (RR, SS) diastereoisomers of haematoporphyrin and the two position isomers 8-(1-hydroxyethyl)-3-vinyldeuteroporphyrin and 3-(1-hydroxyethyl)-8-vinyldeuteroporphyrin. There was no evidence for the involvement of dimers such as dihaematoporphyrin ether.     

Efflux mechanism of taurocholate across the rat intestinal basolateral membrane

We investigated the contribution of multidrug resistance associated protein 3 (Mrp3/ABCC3) to the transport of bile acids across the rat intestinal basolateral membrane using the everted sacs. The permeability-surface area (PS) products of taurocholate in the everted sacs of rat jejunum, ileum, and colon were determined in the absence or presence of inhibitors for Mrp3. The results were analyzed to determine the PS product for the uptake across the apical membrane (PS1) and that for the efflux across the basolateral membrane (PS3). The mucosal-to-serosal transport of taurocholate in the ileum was the highest. The concentration-dependent inhibitory effects by all inhibitors in the ileum were observed on both PS1 and PS3 for taurocholate. However, even in the presence of 1 mM of each inhibitor, the decrease of PS3 was low. Additionally, PS3 in the colon, where Mrp3 is expressed at a high level, was not inhibited by MK571 and taurolithocholate-3-sulfate. Unlike PS1, PS3 did not exhibit saturation at the concentration examined. These results suggest that Mrp3 makes only a minor contribution to the efflux of bile acids across the basolateral membrane. Ostalpha-Ostbeta heteromeric transporter is certainly one of the good candidates for such a transporter.     

A study of unfractionated and low molecular weight heparins in a model of cholestatic liver injury in the rat.

Forty-eight rats with biliary obstruction induced by double ligation and section of the common bile duct were randomly and blindly assigned to receive subcutaneous injection of either conventional heparin sodium (1000IU kg(-1)), three already marketed low molecular weight heparin (LMWH) preparations: nadroparin (1000 anti-Xa IU kg(-1)), tinzaparin (1000 anti-Xa IU kg(-1)), enoxaparin (180 anti-Xa IU kg(-1)) or saline. Drugs were administered once a day, starting 7 days after surgery and continued for 3 weeks. At the end of the treatment period, rats were killed and analyzed for blood biochemistry and liver pathology. Liver fibrosis was assessed by image analysis. Data indicated that treatment with nadroparin decreased plasma total bilirubin, serum alkaline phosphatase (ALP) and gamma glutamyltransferase (GGT) levels by 80.3, 70.7 and 42%, compared with bile duct ligated (BDL) control values. The reduction in plasma total protein observed in BDL controls was prevented by nadroparin. Enoxaparin-treated rats showed significant reduction in plasma total bilirubin and alanine aminotransferase levels by 32.5 and 38.4% versus BDL controls. Liver necrosis evaluated histologically was significantly reduced in the nadroparin- and enoxaparin-treated rats. Morphometric analysis showed significant reduction in fibrosis on nadroparin and enoxaparin treatment: area of fibrosis: 1.66 +/- 0.17% and 14.03 +/- 1.1% versus 18.94 +/- 2.4% (P<0.05); nadroparin and enoxaparin versus BDL control. By contrast, neither conventional heparin nor tinzaparin prevented the bile duct ligation-induced liver damage as indicated by increased plasma aminotransferases, ALP and GGT concentrations and the histological evidence of necrosis. Total serum bilirubin was increased by 27.5% in rats treated with conventional heparin, while ALP and GGT levels were 38.6 and 31.4% higher after tinzaparin treatment versus BDL controls. Significant increase in the area of fibrosis was observed after tinzaparin treatment compared to BDL control group. Results suggest a beneficial effect for nadroparin and enoxaparin in the therapy of patients with obstructive jaundice or cholestatic liver disorders. The present data from bile duct ligated rats suggest an antifibrotic effect for nadroparin and enoxaparin.     

糖皮质激素对淤胆型药物性肝病的疗效

目的比较激素及非激素在治疗严重的淤胆型药物性肝病(DILD)中的作用。方法淤胆型DILD诊断依据为Za-kim分类标准,疗效标准为治疗后血清胆红素降至正常,疗效的显著性比较用t检验进行分析。结果1996～2006年10年间收治的严重淤胆型DILD78例,依据是否应用激素治疗将其分为激素治疗组及非激素治疗组。激素治疗组以激素使用前的总胆红素为基数,非激素治疗组以入院时的总胆红素为基数;以住院期间平均每天总胆红素升高或下降占基数的百分比表示治疗反应。激素治疗组为52例,治愈率为92.31%。非激素治疗组为26例,治愈率为69.23%,在治疗有效的病例中,激素治疗组开始治疗时总胆红素为(354.36±137.68)μmol/L,比非激素治疗组的(254.77±74.51)μmol/L明显为高(P<0.05)。激素治疗组总胆红素每天平均下降速率为3.56%±2.11%,明显快于非激素治疗组的2.12%±1.02%(P<0.05)。结论对于胆汁淤积型DILD,糖皮质激素可以有效减轻淤胆症状,使黄疸消退。     

Plasma antioxidant levels in chronic cholestatic liver diseases

BAKCGROUND: A predictable consequence of cholestasis is malabsorption of fat-soluble factors, (vitamins A, D, E, K) and other free radical scavengers, such as carotenoids. It has been suggested that oxygen-derived free radicals may be involved in the pathogenesis of chronic liver damage. AIMS: (i) To evaluate retinol, alpha-tocopherol and carotenoid plasma levels in two groups of patients with chronic cholestatic liver disease (primary biliary cirrhosis and primary sclerosing cholangitis); (ii) to compare the respective plasma levels with those of the general population; (iii) to correlate the plasma levels with disease severity. METHODS: A total of 105 patients with chronic cholestasis were included in the study: 86 with primary biliary cirrhosis (81 female, five male, mean age 55.5 +/- 11 years), 19 with primary sclerosing cholangitis (seven female, 12 male, mean age 35 +/- 11 years; six patients had associated inflammatory bowel disease); 105 sex- and age-matched subjects from the general population in the same geographical area (88 female, 17 male, mean age 51.3.5 +/- 10 years) served as controls. Carotenoids (lutein zeaxanthin, lycopene, beta-carotene, alpha-carotene, beta-cryptoxanthin), retinol and alpha-tocopherol were assayed by high-pressure liquid chromatography. A food frequency questionnaire was administered to each subject to evaluate the quality and the quantity of dietary compounds. Data were processed by analysis of variance and linear regression analysis, as appropriate. RESULTS: Both primary biliary cirrhosis and primary sclerosing cholangitis patients had significantly lower levels of retinol, alpha-tocopherol, total carotenoids, lutein, zeaxanthin, lycopene, alpha- and beta-carotene than controls (P < 0.0001). Among the cholestatic patients, no significant difference in the concentration of antioxidants was observed between primary biliary cirrhosis and primary sclerosing cholangitis subjects. Anti-oxidant plasma levels were not affected by the severity of the histological stage in primary biliary cirrhosis, but a negative correlation was found between total carotenoids and both alkaline phosphatase (ALP) and gammaglutamyl transpeptidase (GGT) (P < 0.013 and P < 0.018, respectively). Within the primary sclerosing cholangitis group, no correlation was found between total carotenoids and cholestatic enzymes. Nutritional intake in cholestatic patients was comparable to controls, including fruit and vegetable intake. CONCLUSIONS: Although no clinical sign of deficiency is evident, plasma levels of antioxidants are low in cholestatic patients even in early stages of the disease. This is probably due to malabsorption of fat-soluble vitamins, as well as other mechanisms of hepatic release, suggesting the need for dietary supplementation.     

Andrographolide impairs alpha-naphthylisothiocyanate-induced cholestatic liver injury in vivo

To investigate if andrographolide impairs cholestatic liver injury. All rats were randomly divided into six groups—(1) control (n?=?6), (2) control?+?200 mg/kg andrographolide (n?=?6), (3) alpha-naphthylisothiocyanate (ANIT)-control (n?=?6), (4) ANIT?+?50 mg/kg andrographolide (n?=?6), (5) ANIT?+?100 mg/kg andrographolide (n?=?6), and (6) ANIT?+?200 mg/kg andrographolide (n?=?6). We gavaged 50 mg/kg ANIT to mimic cholestatic liver injury in rats. Seven days after treatment, all the rats were killed. Serum biochemistry and hepatic histopathological assays were performed to evaluate liver injury. We observed that 200 mg/kg andrographolide significantly decreased the level of alanine transaminase, aspartate aminotransferase, alkaline phosphatase, γ-glutamyltranspeptidase, total bilirubin, and total bile acid in the blood. It also markedly decreased hepatic interleukin-6 and tumor necrosis factor α. Furthermore, 200 mg/kg andrographolide significantly decreased malondialdehyde but increased superoxide dismutase, glutathione, and erythrocyte glutathione peroxidase. Moreover, 200 mg/kg andrographolide effectively increased the accumulation of sirtuin 1 and nuclear erythroid 2-related factor-2. It also attenuated the level of nuclear factor kappa-light-chain-enhancer of activated B and cyclooxygenase-2. These data suggest that andrographolide may impair cholestatic liver injury via anti-inflammatory and anti-oxidative stress.

     

Inhibition by trichloroethylene and 1,1,2-trichloro-1,2,2-trifluoroethane of taurocholate uptake into basolateral rat liver plasma membrane vesicles

It has previously been shown that trichloroethylene (TRI) and 1,1,2-trichloro-1,2,2-tri-fluoroethane (FC 113) interfere with the transport of bile acids by isolated human and rat hepatocytes in a dose-dependent and reversible manner. This finding may explain the rise in serum bile acids (SBA) following exposure to these chemicals. However, the effect of these compounds on the transport of bile acids across the cellular membrane in the absence of confounding variables, such as interference by intracellular metabolism, binding to cytosolic proteins and intracellular conjugation, has not been investigated. Accordingly, in vitro effects of TRI and FC 113 on uptake of [³H]taurocholate (TC) into purified basolateral (blLPM) and canalicular (cLPM) rat liver plasma membrane vesicles were examined by a rapid filtration technique. Both TRI and FC 113 caused a dose-dependent inhibition of TC uptake into blLPM vesicles at an approximate concentration of 3 m and 72 μ , respectively. Initial rates of TC uptake in the presence of TRI and FC 113 were significantly inhibited by 69 and 61%, respectively (P< 0.05). In contrast, these chemicals had no effect on TC uptake into cLPM vesicles. This confirms studies in intact cells where these solvents were found to inhibit the uptake of bile acids by hepatocytes rather than interfere with the process of efflux. In conclusion, and consistent with the previous findings, the data suggest that the mechanism of TRI and FC 113-induced elevation of SBA may, in part, be due to selective inhibition of bile acid transport by the parent compounds at the basolateral domain of the hepatocyte plasma membrane.     

Hepatic transport of bile acids in the isolated perfused rat liver. Structure-kinetic relationship

We studied the transport kinetics of a series of bile acids from blood to bile in the isolated perfused rat liver in order to define better the relationship between chemical structure of bile acid molecules and efficiency of the overall hepatic transport process. BA studied were taurocholate (TC), glycocholate (GC), cholate (C), tauroursodeoxycholate (TUDC), ursodeoxycholate (UDC) and hyodeoxycholate (HDC). Estimates of intrinsic hepatic clearance (Cl(int)), maximal secretory rate (Vmax) were provided from the analysis of the relationship between bile acid removal rates and sinusoidal concentration under steady-state conditions. TC and TUDC had the highest Cl(int) (about 5 ml/min/g liver) and Vmax (about 800 nmol/min/g liver) followed in order by GC (1.71 ml/min/g liver; 442 nmol/min/g liver); C (1.25 ml/min/g liver; 252 nmol/min/g liver); HDC (0.86 ml/min/g liver; 238 nmol/min/g liver); UDC (0.72 ml/min/g liver; 176 nmol/min/g liver). The findings suggest that the efficiency of the overall hepatic transport of bile acids is highly dependent on their molecular structure and that conjugation has a more important effect on both Cl(int) and Vmax that the number or position of hydroxyl groups.