Effect Of Bile Duct Ligation Research Articles

Oleuropein can Protect the Brain Against Deleterious Effects of Bile Duct Ligation in Male Mice

Oleuropein (OP) is a phenolic compound in olives. OP possesses potent antioxidant activity and an extensive spectrum of other pharmacological properties, including antiviral, anti-inflammatory, and antimicrobial activities. This study investigated the effects of OP on neural injuries caused by bile duct ligation (BDL) in male mice. The mice were randomly allocated to three groups: sham, BDL, and BDL + OP. Neurobehavioral tests histological and biochemical evaluations were accomplished to assess cerebral damage. The results demonstrated that the induction of BDL led to behavioral impairments and a rise in hepatic enzymes, and OP could protect the brain against BDL-induced injuries. OP significantly increased antioxidant enzymes. These results suggested that OP has valuable effects in the mice BDL model, probably due to its anti-inflammatory and antioxidant properties.

Effects of bile duct ligation on the inhibitory control of supraoptic vasopressin neurons.

Dilutional hyponatremia due to increased plasma arginine vasopressin (AVP) is associated with liver cirrhosis. However, plasma AVP remains elevated despite progressive hypoosmolality. This study investigated changes to inhibitory control of supraoptic nucleus (SON) AVP neurons during liver cirrhosis. Experiments were conducted with adult male Sprague-Dawley rats. Bile duct ligation was used as a model of chronic liver cirrhosis. An adeno-associated virus containing a construct with an AVP promoter and either green fluorescent protein (GFP) or a ratiometric chloride indicator, ClopHensorN, was bilaterally injected into the SON of rats. After 2 weeks, rats received either BDL or sham surgery, and liver cirrhosis was allowed to develop for 4 weeks. In vitro, loose patch recordings of action potentials were obtained from GFP-labeled and unlabeled SON neurons in response to a brief focal application of the GABAA agonist muscimol (100 μM). Changes to intracellular chloride ([Cl]i) following muscimol application were determined by changes to the fluorescence ratio of ClopHensorN. The contribution of cation chloride cotransporters NKCC1 and KCC2 to changes in intracellular chloride was investigated using their respective antagonists, bumetanide (BU, 10 μM) and VU0240551 (10 μM). Plasma osmolality and hematocrit were measured as a marker of dilutional hyponatremia. The results showed reduced or absent GABAA -mediated inhibition in a greater proportion of AVP neurons from BDL rats as compared to sham rats (100% inhibition in sham vs. 47% in BDL, p = .001). Muscimol application was associated with increased [Cl]i in most cells from BDL as compared to cells from sham rats (χ2 = 30.24, p < .001). NKCC1 contributed to the impaired inhibition observed in BDL rats (p < .001 BDL - BU vs. BDL + BU). The results show that impaired inhibition of SON AVP neurons and increased intracellular chloride contribute to the sustained dilutional hyponatremia in liver cirrhosis.

Neurometabolic changes in a rat pup model of type C hepatic encephalopathy depend on age at liver disease onset

Chronic liver disease (CLD) is a serious condition where various toxins present in the blood affect the brain leading to type C hepatic encephalopathy (HE). Both adults and children are impacted, while children may display unique vulnerabilities depending on the affected window of brain development.We aimed to use the advantages of high field proton Magnetic Resonance Spectroscopy (1H MRS) to study longitudinally the neurometabolic and behavioural effects of Bile Duct Ligation (animal model of CLD-induced type C HE) on rats at post-natal day 15 (p15) to get closer to neonatal onset liver disease. Furthermore, we compared two sets of animals (p15 and p21-previously published) to evaluate whether the brain responds differently to CLD according to age onset.We showed for the first time that when CLD was acquired at p15, the rats presented the typical signs of CLD, i.e. rise in plasma bilirubin and ammonium, and developed the characteristic brain metabolic changes associated with type C HE (e.g. glutamine increase and osmolytes decrease). When compared to rats that acquired CLD at p21, p15 rats did not show any significant difference in plasma biochemistry, but displayed a delayed increase in brain glutamine and decrease in total-choline. The changes in neurotransmitters were milder than in p21 rats. Moreover, p15 rats showed an earlier increase in brain lactate and a different antioxidant response. These findings offer tentative pointers as to which neurodevelopmental processes may be impacted and raise the question of whether similar changes might exist in humans but are missed owing to 1H MRS methodological limitations in field strength of clinical magnet.

Effects of Bile Duct Ligation and Ghrelin Treatment on the Colonic Barrier and Microbiome of Mice

Introduction: Cholestatic liver disease (CLD) is associated with intestinal barrier dysfunction. The peptide hormone ghrelin may exert both hepatoprotective and barrier-strengthening effects. Here, we have evaluated these effects under the conditions of experimental cholestasis. Methods: C57BL/6J mice with bile duct ligation (BDL) or sham surgery were treated with ghrelin or solvent for 9 days. Liver injury was assessed by histological and laboratory analyses. Paracellular macromolecule permeability and transmural electrical resistance (TMER) of colonic tissues were measured using a Ussing chamber. Expression of tight junction (TJ) genes was quantified by real-time PCR. Amplicon metagenomic sequencing was employed to analyze bacterial 16S rRNA from colonic stool samples. Results: Mice with BDL exhibited weight loss and signs of severe liver injury. These changes were unaffected by ghrelin treatment. FITC-4-kDa-dextran flux was increased and TMER decreased after BDL. Treatment with ghrelin tended to reduce these effects. Furthermore, application of ghrelin was associated with higher mRNA levels of claudin-4, occludin, and ZO-1 in colonic tissues of mice with BDL. Reduced alpha-diversity of the microbiome was observed in solvent-treated mice with BDL but not in ghrelin-treated animals. Conclusion: Ghrelin treatment did not improve weight loss and liver damage but increased gene expression of colonic TJ proteins and restored the alpha-diversity of the microbiome. Since protective effects of ghrelin might be masked by the severity of the model, we suggest follow-up studies in models of milder CLD.

Increased Expression of Adherens Junction Components in Mouse Liver following Bile Duct Ligation.

Adherens junctions, consisting of cadherins and catenins, are a group of cell-to-cell junctions that mediate mechanistic linkage between neighboring cells. By doing so, adherens junctions ensure direct intercellular contact and play an indispensable role in maintaining tissue architecture. Considering these critical functions, it is not surprising that adherens junctions are frequently involved in disease. In the present study, the effects of bile duct ligation—a surgical procedure to experimentally induce cholestatic and fibrotic liver pathology—on hepatic adherens junctions were investigated in mice. In essence, it was found that liver mRNA and protein levels of E-cadherin, β-catenin and γ-catenin drastically increase following bile duct ligation. These results could suggest a cytoprotective role for hepatic adherens junctions following bile duct ligation.

The effects of bile duct ligation on motor cortex region morphology and aquaporin 4 protein concentration in male Wistar rats

The effects of bile duct ligation on motor cortex region morphology and aquaporin 4 protein concentration in male Wistar rats

Progressive dysfunction of collecting liver lymphatics during the development of extrahepatic cholestasis

Lymphatics are necessary anatomical structures of body systems to maintain tissue fluid and molecular homeostasis and are tightly involved in immune reactions of the body. Transport function of lymphatics is altered during inflammation, which impacts the pathogenesis of many diseases. Despite their importance in liver function, the functional characteristics of liver lymphatic vessels (LLVs) have not been evaluated. In this study we, for the first time, measured the function of LLVs in normal and cholestatic rats following extrahepatic bile duct ligation (BDL). In this study parameters of lymphatic contractility/pumping of isolated, cannulated and pressurized segments of LLVs were determined in male 5 moth old Sprague‐Dawley rats. The following animal groups were used: control, 1, 3 and 7 days, after BDL (BDL1, BDL3 and BDL7) and sham control 3 days after surgery. Segments of LLVs located in close proximity to the liver were dissected for the study. Lymphatic contractility parameters were measured and analyzed in isolated, cannulated and pressurized LLV segments under standard transmural pressures and imposed flow ranges in all groups. Healthy LLVs with outer diameter of ~500±50 μm have significant lymphatic tone (7–9%), moderate contraction amplitude (10–25%), high contraction frequency (14–25 contractions/min) demonstrating therefore strong pumping (4–7 volumes/min). Contractility of LLVs from sham and control group were not significantly different. BDL induced specific changes in tone and phasic contractions of LLVs. BDL caused an increase in vessel size (up to 900±100 μm of outer diameter in BDL7 group), progressive lowering of lymphatic tone over period of time after BDL (up to ~2–3‐fold lower lymphatic tone in BDL7 group). Effects of BDL on lymphatic contraction amplitude were as follows: BDL1‐LLVs contraction amplitude was ~2–2.5 times higher than control, BDL3– back to control values, BDL7– amplitude was 0 (a complete cessation of phasic contractions). At the same time contraction frequency in BDL1 and BDL3 LLVs was ~2–2.2 fold lower than control with no contractions in BDL7 group. Cumulatively, we observed a progressive decline in LLVs' pumping in BDL1 and BDL3 groups with complete lymphatic pump failure in BDL7 group. Additionally, LLVs possess comparatively light flow‐dependent responses, which were ablated by BDL. The data indicate that over the time course of cholestasis, the transport capabilities of LLVs are progressively diminished introducing severe, harmful disturbances in fluid/macromolecular homeostasis of the cholestatic liver, which could alter proper trafficking of immune cells and promote liver inflammation. Further research on underlying mechanisms of liver lymphatic dysfunction will shed light on the pathogenesis of cholestatic liver disease and may reveal novel therapeutic approaches.Support or Funding Information1U01HL123420 (DZ, AG); DK110035 (SG, GA)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A disposition kinetic study of Tramadol in bile duct ligated rats in perfused rat liver model.

Tramadol hydrochloride is a centrally acting synthetic opioid analgesic drug and is used to treat chronic pain. In this study, the effects of Bile Duct Ligation (BDL) on the pharmacokinetics of tramadol in a liver recirculating perfusion system of male rats were used. Twenty-four Wistar male rats were randomly divided into four groups: control, sham and two weeks BDL and four weeks BDL. Serum levels of liver enzymes were measured before perfusion and the pharmacokinetics of tramadol was evaluated by using liver recirculating perfusion system. Tramadol and metabolites concentrations were determined by HPLC-FL. The sharp increase in liver enzymes level in both BDL groups was observed and significant changes were also observed in liver weight and volume. Tramadol metabolites concentration significantly decreased compared with the control and sham group (P<0.05). The decrease in the hepatic metabolism of tramadol and increase in the half-life of the elimination of tramadol in rats with BDL suggests that personalized treatment and the therapeutic drug monitoring (TDM) data examination are necessary for patients with bile duct diseases and the dose of tramadol should be accordingly adjusted.

17β-Estradiol in the systemic circulation derives mainly from the parietal cells in cholestatic female rats.

Estrogenic symptoms of liver disease patients including biliary tract disorder with high frequency is observed in clinical cases. However, the origin of 17β-estradiol which is abundant enough to cause symptoms remains uncertain. In male rats, it has been reported that the parietal cells which have an abundance of aromatase-synthesized 17β-estradiol, and a part of 17β-estradiol secreted into the portal vein, may flow into the systemic circulation under a pathophysiological condition of the liver including bile duct ligation (BDL). The aim of this study is to reveal the origin of 17β-estradiol increment in female rats and to investigate the effect of BDL on the ovary during the estrus cycle. Wistar female rats were used, and the common bile duct was ligated twice and transected completely at 7 days before termination. Serum portal venous and arterial 17β-estradiol levels, Cyp19a1 expressions, aromatase protein levels, and estrogen receptor (ER) α levels in the liver were measured during the estrus cycle. Both arterial and portal venous 17β-estradiol levels increased 2.9 times at proestrus and maintained constant levels during the cycle. The expression of Cyp19a1 and aromatase protein in the stomach maintained constant levels, and significantly decreased during the estrus cycle in the ovary. Hepatic ERα protein and Esr1 expressions decrease by BDL in all stages. These results suggest that the increment of serum 17β-estradiol levels in obstructive cholestasis induced by BDL is derived from 17β-estradiol secreted from the parietal cells in females as well as males.

Effects of bile duct ligation and cholic acid treatment on fatty liver in two rat models of non-alcoholic fatty liver disease

BackgroundNon-alcoholic fatty liver disease, one of the most prevalent liver disorders in Western countries, is characterized by hepatic accumulation of triglycerides. Bile acids have long been known to affect triglyceride homeostasis through a not completely understood mechanism. AimTo analyse the effects of two different manipulations of bile acid circulation on non-alcoholic fatty liver disease. MethodsTwo animal models of non-alcoholic fatty liver disease were developed by either feeding rats with a choline deficient or with a high fat diet. After 4 weeks, rats were randomized to undergo either bile duct ligation, sham operation or cholic acid administration. ResultsDuring cholestasis there was an increased CYP7A1 expression, the rate limiting enzyme in bile acid synthesis, and a reduction of hepatic concentration of oxysterols, ligands of the liver X receptors. Target genes of the liver X receptors, involved in fatty acid and triglyceride synthesis, were down-regulated in association with decreased hepatic triglyceride content and improvement of fatty liver. Administration of cholic acid, ligand of farnesoid X receptor, also had a beneficial effect on fatty liver in rats on choline deficient diet. ConclusionThese results indicate that pharmacological approaches increasing the expression of CYP7A1 or stimulating farnesoid X receptor pathway could represent a promising treatment for non-alcoholic fatty liver disease.

Effect of bile duct ligation on bile acid composition in mouse serum and liver

Cholestatic liver diseases can be caused by genetic defects, drug toxicities, hepatobiliary malignancies or obstruction of the biliary tract. Cholestasis leads to accumulation of bile acids (BAs) in hepatocytes. Direct toxicity of BAs is currently the most accepted hypothesis for cholestatic liver injury. However, information on which bile acids are actually accumulating during cholestasis is limited. To assess the BA composition in liver and serum after bile duct ligation (BDL) in male C57Bl/6 mice between 6h and 14days and evaluate toxicity of the most abundant BAs. Bile acid concentrations increased in liver (27-fold) and serum (1400-fold) within 6h after surgery and remained elevated up to 14days. BAs in livers of BDL mice became more hydrophilic than sham controls, mainly because of increased 6β-hydroxylation and taurine conjugation. Among the eight unconjugated and 16 conjugated BAs identified in serum and liver, only taurocholic acid (TCA), β-muricholic acid (βMCA) and TβMCA were substantially elevated representing >95% of these BAs over the entire time course. Although glycochenodeoxycholic acid and other conjugated BAs increased in BDL animals, the changes were several orders of magnitude lower compared with TCA, βMCA and TβMCA. A mixture of these BAs did not cause apoptosis or necrosis, but induced inflammatory gene expression in cultured murine hepatocytes. The concentrations of cytotoxic BAs are insufficient to cause hepatocellular injury. In contrast, TCA, βMCA and TβMCA are able to induce pro-inflammatory mediators in hepatocytes. Thus, BAs act as inflammagens and not as cytotoxic mediators after BDL in mice.

Obstructive Jaundice Expands Intrahepatic Regulatory T Cells, Which Impair Liver T Lymphocyte Function but Modulate Liver Cholestasis and Fibrosis

Although obstructive jaundice has been associated with a predisposition toward infections, the effects of bile duct ligation (BDL) on bulk intrahepatic T cells have not been clearly defined. The aim of this study was to determine the consequences of BDL on liver T cell phenotype and function. After BDL in mice, we found that bulk liver T cells were less responsive to allogeneic or syngeneic Ag-loaded dendritic cells. Spleen T cell function was not affected, and the viability of liver T cells was preserved. BDL expanded the number of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg), which were anergic to direct CD3 stimulation and mediated T cell suppression in vitro. Adoptively transferred CD4(+)CD25(-) T cells were converted into Treg within the liver after BDL. In vivo depletion of Treg after BDL restored bulk liver T cell function but exacerbated the degrees of inflammatory cytokine production, cholestasis, and hepatic fibrosis. Thus, BDL expands liver Treg, which reduce the function of bulk intrahepatic T cells yet limit liver injury.

Endoglin Upregulation in the Liver after Bile Duct Ligation in Rats

Background: Transforming growth factor beta 1 (TGF- 1) has been implicated in the stimulation of extracellu- lar matrix synthesis in acute and chronic liver disease. Endoglin (CD-105) is a membrane glycoprotein that binds TGF- 1 with high affinity. Endoglin is overexpressed in several model of fibrosis. The goal of the present study was to evaluate the effect of bile duct ligation (BDL) on endoglin expression and the effect of endoglin overexpression on liver fibrosis in rats. Methods: Rat livers were transfected with a vector containing full length human endoglin (h-end) or an empty vector (mock) and 48 hours after were subjected to either BDL or sham operation (SO). Eighteen days after, a blood sample was obtained and bilirubin and serum enzyme activities were measured to assess liver damage. Liver fibrosis was quantified by a computer-assisted image analysis of Sirius red stained livers and by liver hydroxyproline content. Endoglin expres- sion in the liver tissue was assessed by Western blot and immunohystochemistry. Results: Both immunohistochemistry and Western blot reveals endoglin upregulation after BDL in rats. In addition, these techniques also reveal effective human endoglin transfection in the rat's liver. After BDL, liver fibrosis and plasma levels of enzymes were similar in h-end transfected and mock-transfected rats. Western blots showed higher endoglin expression after BDL in h-end transfected and mock-transfected rats. Conclusions: The present study provides clear evidence that endoglin is upregulated in the liver of rats with BDL. h-end overexpression did not improve liver fibrosis after BDL in rats.

Effects of Bile Duct Ligation (BDL) and Enalapril on Angiotensin receptors in the Subfornical Organ (SFO) in Rats

Inappropriate vasopressin (AVP) release causes fluid retention, ascites, and dilutional hyponatremia associated with cirrhosis. Although the central molecular mechanisms that mediate inappropriate AVP release are not clear, plasma angiotensin II (AngII) has been implicated as a factor in the pathogenesis of dilutional hyponatremia. To better understand the relationship between the CNS effects of circulating AngII and increased AVP release during cirrhosis, we examined the effects of BDL with treatment of enalapril on AT1R expression in the SFO. Starting the 21st day after BDL surgery BDL rats were either treated with enalapril dissolved in tap water (0.25mg/mL) or with normal tap water. On the 28th day (after 7 days of enalapril treatment), the rats were anesthetized, decapitated and brain punches were taken of the SFO for quantification of AT1R. Western Blot analysis showed an increase in AT1R in the SFO of untreated BDL rats as compared to sham ligated controls. In enalapril treated BDL rats, AT1R decreased compared to drug naïve BDL rats. Plasma osmolality and hematocrit also showed a trend towards normalization in enalapril treated BDL rats. These results are consistent with the hypothesis that AngII may increase excitatory drive in the SFO through upregulation of its AT1R thus leading to a decompensation of sodium balance and hyponatremia. (R01 HL062576)

Inhibition of Hemoxygenase-1 Improves Survival after Liver Resection in Jaundiced Rats

Background: The role of hemoxygenase (HO)-1 after partial liver resection (PLR) in jaundiced animals has yet to be defined. We therefore investigated: (1) the acute effects of bile duct ligation (BDL) on bilirubin accumulation and hepatocellular integrity after PLR; (2) how BDL and PLR affect HO-1 protein expression; (3) how functional HO-1 blockade affects survival and liver regeneration after BDL and PLR. Methods: Male Sprague-Dawley rats were subjected to BDL or a sham operation. After 3 days, a 70% hepatectomy was performed. In a second set of experiments, BDL animals received either Sn(IV) mesoporphyrin IX dichloride (SnMP) for HO-1 blockade or a vehicle. Three days later, PLR was performed and survival of the animals was observed for 7 days. Results: PLR, BDL and both together cause a hepatocellular injury and HO-1 expression. Inhibition of HO-1 with SnMP in jaundiced rats that underwent PLR was associated with improved survival, attenuated postoperative weight loss and better liver synthesis. Conclusion: The present findings add further evidence that the protective properties of increased HO-1 expression largely depend on the model used, and that HO-1 overexpression in the model of liver resection during acute cholestasis may also be detrimental.

Effect of bile duct obstruction on the expression of intestinal mRNA related to cholesterol and bile acid metabolism in the rat

The liver and small intestine play an important role in maintaining cholesterol and bile acid balance within the body. The purpose of this study was to evaluate the effect of bile duct ligation (BDL) on the expression of intestinal and hepatic genes that are important for cholesterol and bile acid metabolism. Rats were allocated to the BDL group or the sham operation group. Blood, liver and small intestine were obtained after 24, 72 and 168 h from both groups. Serum and hepatic lipids were measured by colorimetric assays and hepatic and intestinal mRNA related to lipid metabolism was studied by reverse transcription-polymerase chain reaction (RT-PCR). Hepatic apolipoprotein (Apo) AIV, multidrug resistant protein (Mrp)2, adenosine triphosphate (ATP) binding cassette transporter (Abc)g5 and Abcg8 expression constantly decreased after BDL. Intestinal Apo AIV, Apo CIII, Mrp2, Abcg5 and Abcg8 expression remarkably decreased 24 h after BDL and recovered 72 and 168 h after BDL. Hepatic small heterodimer partner (Shp) expression did not change after BDL. Conversely, intestinal Shp expression remarkably decreased 24 h after BDL (16% of sham operation) and slightly recovered 168 h after BDL (58% of sham operation). Several intestinal mRNA expressions important for lipid (Apo AIV, Apo CIII, Abcg5 and Abcg8) and bile acid (Mrp2 and Shp) metabolism were decreased in the early phase of obstructive jaundice and the expression of these intestinal mRNA recovered in the late phase of obstructive jaundice.

Renal elimination of p-aminohippurate (PAH) in response to three days of biliary obstruction in the rat. The role of OAT1 and OAT3

Pharmacokinetic studies of the drugs administered to subjects with mechanical cholestasis are scarce. The purpose of the present study was to examine the effects of bile duct ligation of 3 days (peak of elevation of serum bile acids and bilirubin) on the systemic and renal PAH clearance and on the expression of cortical renal OAT1 and OAT3 in a rat model. PAH is the prototypical substrate of the renal organic anion transport system. Male Wistar rats underwent a bile duct ligation (BDL rats). Pair-fed sham-operated rats served as controls. BDL rats displayed a significantly lower systemic PAH clearance. Renal studies revealed a reduction in the renal clearance and in the excreted and secreted load of PAH in BDL rats. The OAT1 protein expression in kidney homogenates was not modified, but it decreased in the basolateral membranes from BDL rats. In contrast, OAT3 abundance in both kidney cortex homogenates and in basolateral membranes increased by 3 days after the ligation. Immunocytochemical studies (light microscopic and confocal immunofluorescence microscopic analyses) confirmed the changes in the renal expression of these transport proteins. The present study demonstrates the key role of OAT1 expression in the impaired elimination of PAH after 3 days of obstructive cholestasis.

Biliary Obstruction Selectively Expands and Activates Liver Myeloid Dendritic Cells

Obstructive jaundice is associated with immunologic derangements and hepatic inflammation and fibrosis. Because dendritic cells (DCs) play a major role in immune regulation, we hypothesized that the immunosuppression associated with jaundice may result from the functional impairment of liver DCs. We found that bile duct ligation (BDL) in mice expanded the myeloid subtype of liver DCs from 20 to 80% of total DCs and increased their absolute number by >15-fold. Liver myeloid DCs following BDL, but not sham laparotomy, had increased Ag uptake in vivo, high IL-6 secretion in response to LPS, and enhanced ability to activate T cells. The effects of BDL were specific to liver DCs, as spleen DCs were not affected. Expansion of liver myeloid DCs depended on Gr-1(+) cells, and we implicated monocyte chemotactic protein-1 as a potential mediator. Thus, obstructive jaundice selectively expands liver myeloid DCs that are highly functional and unlikely to be involved with impaired host immune responses.

Failure of macrophage activation in experimental obstructive jaundice: association with bacterial translocation.

Bacterial translocation from the gastrointestinal tract and macrophage activation are central to current theories of sepsis. The relevance of both in obstructive jaundice is unclear. The effect of bile duct ligation for 7 days on bacterial translocation to mesenteric lymph nodes and on macrophage activation in a rat model was examined. Compared with an incidence of zero in sham-ligated controls, bile-duct ligated rats had a 67 per cent incidence of Gram-negative colonization of mesenteric lymph nodes. This was associated with a significant (P < 0.001) decrease in macrophage tumour necrosis factor, superoxide anion and nitric oxide production compared with that in sham controls. Spontaneous bacterial translocation occurs in experimental obstructive jaundice and is associated with marked suppression of macrophage activation. This suggests a mechanism whereby jaundiced patients may be more susceptible to persistent infection but relatively protected against uncontrolled sepsis.

Tissue distribution and induction of the rat multidrug resistance-associated proteins 5 and 6

Multidrug resistance-associated proteins (Mrps) are ATP-dependent transporters which transport a wide variety of anionic and cationic compounds. The purpose of this study was to determine the tissue distribution of Mrp5 and 6 in male and female Sprague–Dawley rats in various tissues, and to investigate whether the expression is altered by cholestasis or administration of microsomal enzyme inducers (MEIs). These MEIs activate six different transcriptionally-mediated pathways, and their effects on Mrp5 and Mrp6 expression were determined. The effects of bile-duct ligation, a cholestasis model, on Mrp5 and 6 expression in male rats were quantified. Mrp5 had marked expression in adrenal gland, and moderate expression in cerebral cortex, cerebellum, and stomach. The MEIs polychlorinated biphenyl (PCB)126, phenobarbital, and PCB99 slightly repressed Mrp5, but no single class of receptor agonists induced or repressed Mrp5. Bile-duct ligation tended to increase Mrp5 expression, but was not statistically significant at a 3 day timepoint. Mrp6 expression was highest in intestine, liver, and kidney. Mrp6 was slightly repressed by phenobarbital, dexamethasone, and isoniazid, but no one class of receptor agonists induced or repressed Mrp6, and expression was also unchanged bile-duct ligation. In conclusion, Mrp5 in rats is most highly expressed in the adrenal gland, whereas Mrp6 is mainly expressed in excretory organs (liver, intestine, and kidney), suggesting markedly different functions. Hepatic mRNA levels of Mrp5 or Mrp6 do not seem to be coordinately regulated along with Phase I enzymes via receptor-mediated pathways, and are not part of the hepatoprotective upregulation of basolateral transporters that occurs during cholestasis.