Application of Pharmacokinetic Modeling to Characterize Hepatobiliary Disposition of Imaging Agents and Alterations due to Liver Injury in Isolated Perfused Rat Livers.

BACKGROUND: Understanding the impact of altered hepatic uptake and/or efflux on the hepatobiliary disposition of the imaging agents [99mTc]Mebrofenin (MEB) and [153Gd]Gadobenate dimeglumine (BOPTA) is important for proper estimation of liver function. METHODS: A multi-compartmental pharmacokinetic (PK) model describing MEB and BOPTA disposition in isolated perfused rat livers (IPRLs) was developed. The PK model was simultaneously fit to MEB and BOPTA concentration-time data in the extracellular space, hepatocytes, bile canaliculi, and sinusoidal efflux in livers from healthy rats, and to BOPTA concentration-time data in rats pretreated with monocrotaline (MCT). RESULTS: The model adequately described MEB and BOPTA disposition in each compartment. The hepatocyte uptake clearance was much higher for MEB (55.3 mL/min) than BOPTA (6.67 mL/min), whereas the sinusoidal efflux clearance for MEB (0.000831 mL/min) was lower than BOPTA (0.0127 mL/min). The clearance from hepatocytes to bile (CLbc) for MEB (0.658 mL/min) was similar to BOPTA (0.642 mL/min) in healthy rat livers. The BOPTA CLbc was reduced in livers from MCT-pretreated rats (0.496 mL/min), while the sinusoidal efflux clearance was increased (0.0644 mL/min). CONCLUSION: A PK model developed to characterize MEB and BOPTA disposition in IPRLs was used to quantify changes in the hepatobiliary disposition of BOPTA caused by MCT pretreatment of rats to induce liver toxicity. This PK model could be applied to simulate changes in the hepatobiliary disposition of these imaging agents in rats in response to altered hepatocyte uptake or efflux associated with disease, toxicity, or drug-drug interactions.

Monocrotaline Toxicity Alters the Function of Hepatocyte Membrane Transporters in Rats.

Pyrrolizidine alkaloid monocrotaline (MCT) induces sinusoidal obstruction syndrome (SOS) in rats characterised by a sinusoidal congestive obstruction. Additionally, MCT administration decreases the biliary excretion of gadobenate dimeglumine (BOPTA), a hepatobiliary substrate used in clinical imaging. BOPTA crosses hepatocyte membranes through organic anion transporting polypeptides, multidrug-resistance-associated protein 2, and Mrp3/4 transporters, and a modified function of these transporters is likely to explain the decreased biliary excretion. This study compared BOPTA transport across hepatocytes in livers isolated from normal (Nl) rats and rats with intragastric administration of MCT. BOPTA hepatocyte influx clearance was similar in both groups, while biliary clearance and bile concentrations were much lower in MCT than in Nl livers. BOPTA efflux clearance back to the sinusoids compensated for the low biliary excretion, and hepatocyte concentrations remained similar in both groups. This SOS-associated changes of transporter functions might impact the pharmacokinetics of numerous drugs that use similar transporters to cross hepatocytes.

New Pharmacokinetic Parameters of Imaging Substrates Quantified from Rat Liver Compartments.

Hepatobiliary imaging is increasingly used by pharmacologists to quantify liver concentrations of transporter-dependent drugs. However, liver imaging does not quantify concentrations in extracellular space, hepatocytes, and bile canaliculi. Our study compared the compartmental distribution of two hepatobiliary substrates gadobenate dimeglumine [BOPTA; 0.08 liver extraction ratio (ER)] and mebrofenin (MEB; 0.93 ER) in a model of perfused rat liver. A gamma counter placed over livers measured liver concentrations. Livers were preperfused with gadopentetate dimeglumine to measure extracellular concentrations. Concentrations coming from bile canaliculi and hepatocytes were calculated. Transporter activities were assessed by concentration ratios between compartments and pharmacokinetic parameters that describe the accumulation and decay profiles of hepatocyte concentrations. The high liver concentrations of MEB relied mainly on hepatocyte and bile canaliculi concentrations. In contrast, the three compartments contributed to the low liver concentrations obtained during BOPTA perfusion. Nonlinear regression analysis of substrate accumulation in hepatocytes revealed that cellular efflux is measurable ∼4 minutes after the start of perfusion. The hepatocyte-to-extracellular concentration ratio measured at this time point was much higher during MEB perfusion. BOPTA transport by multidrug resistance associated protein 2 induced an aquaporin-mediated water transport, whereas MEB transport did not. BOPTA clearance from hepatocytes to bile canaliculi was higher than MEB clearance. MEB did not efflux back to sinusoids, whereas BOPTA basolateral efflux contributed to the decrease in hepatocyte concentrations. In conclusion, our ex vivo model quantifies substrate compartmental distribution and transport across hepatocyte membranes and provides an additional understanding of substrate distribution in the liver. SIGNIFICANCE STATEMENT: When transporter-dependent drugs target hepatocytes, cellular concentrations are important to investigate. Low concentrations on cellular targets impair drug therapeutic effects, whereas excessive hepatocyte concentrations may induce cellular toxicity. With a gamma counter placed over rat perfused livers, we measured substrate concentrations in the extracellular space, hepatocytes, and bile canaliculi. Transport across hepatocyte membranes was calculated. The study provides an additional understanding of substrate distribution in the liver.

Hepatocyte Concentrations of Imaging Compounds Associated with Transporter Inhibition: Evidence in Perfused Rat Livers.

In the liver, several approaches are used to investigate and predict the complex issue of drug-induced transporter inhibition. These approaches include in vitro assays and pharmacokinetic models that predict how inhibitors modify the systemic and liver concentrations of the victim drugs. Imaging is another approach that shows how inhibitors might alter liver concentrations stronger than systemic concentrations. In perfused rat livers associated with a gamma counter that measures liver concentrations continuously, we previously showed how fluxes across transporters generate the hepatocyte concentrations of two clinical imaging compounds, one with a low extraction ratio [gadobenate dimeglumine (BOPTA)] and one with a high extraction ratio [mebrofenin (MEB)]. BOPTA and MEB are transported by rat organic anion transporting polypeptide and multiple resistance-associated protein 2, which are both inhibited by rifampicin. The aim of the study is to measure how rifampicin modifies the hepatocyte concentrations and membrane clearances of BOPTA and MEB and to determine whether these compounds might be used to investigate transporter-mediated drug-drug interactions in clinical studies. We show that rifampicin coperfusion greatly decreases BOPTA hepatocyte concentrations, but increases those of MEB. Rifampicin strongly decreases BOPTA hepatic clearance. In contrast, rifampicin decreases moderately MEB hepatic clearance and blocks the biliary intrinsic clearance, increasing MEB hepatocyte concentrations. In conclusion, low concentrations prevent the quantification of BOPTA biliary intrinsic clearance, while MEB is a promising imaging probe substrate to evidence transporter-mediated drug-drug interactions when inhibitors act on influx and efflux transporters.

Quantification of hepatic perfusion and hepatocyte function with dynamic gadoxetic acid-enhanced MRI in patients with chronic liver disease.

The purpose of the present study was to develop and perform initial validation of dynamic MRI enhanced with gadoxetic acid as hepatobiliary contrast agent to quantify hepatic perfusion and hepatocyte function in patients with chronic liver disease. Free-breathing, dynamic gadoxetic acid-enhanced MRI was performed at 3.0 T using a 3D time-resolved angiography sequence with stochastic trajectories during 38 min. A dual-input three-compartment model was developed to derive hepatic perfusion and hepatocyte function parameters. Method feasibility was assessed in 23 patients with biopsy-proven chronic liver disease. Parameter analysis could be performed in 21 patients (91%). The hepatocyte function parameters were more discriminant than the perfusion parameters to differentiate between patients with minimal fibrosis (METAVIR F0-F1), intermediate fibrosis (F2-F3) and cirrhosis (F4). The areas under the receiver operating characteristic curves (ROCs) to diagnose significant fibrosis (METAVIR F ≥ 2) were: 0.95 (95% CI: 0.87-1; P<0.001) for biliary efflux, 0.88 (95% CI: 0.73-1; P<0.01) for sinusoidal backflux, 0.81 (95% CI: 0.61-1; P<0.05) for hepatocyte uptake fraction and 0.75 (95% CI: 0.54-1; P<0.05) for hepatic perfusion index (HPI), respectively. These initial results in patients with chronic liver diseases show that simultaneous quantification of hepatic perfusion and hepatocyte function is feasible with free breathing dynamic gadoxetic acid-enhanced MRI. Hepatocyte function parameters may be relevant to assess liver fibrosis severity.

Liver Perfusion Modifies Gd-DTPA and Gd-BOPTA Hepatocyte Concentrations Through Transfer Clearances Across Sinusoidal Membranes.

BACKGROUND AND OBJECTIVES: Gadobenate dimeglumine (Gd-BOPTA) is a commercialised hepatobiliary contrast agent used during liver magnetic resonance imaging (MRI) to detect liver diseases. It enters into human hepatocytes through organic anion transporting polypeptides (OATP1B1/B3) and crosses the canalicular transporter multiple resistance-associated protein 2 (MRP2) to be excreted into bile canaliculi. Gd-BOPTA can return to sinusoids via the sinusoidal transporters MRP3/MRP4. Hepatocyte concentrations of Gd-BOPTA depend on three clearances: the sinusoidal clearance or volume of sinusoidal blood cleared of drugs per unit of time and two hepatocyte clearances (into bile canaliculi or back to sinusoids) or volume of hepatocytes cleared of drugs per unit of time in the respective liver compartments. The present study investigates whether changing liver blood flow modifies hepatocyte concentrations when plasma concentrations do not change. METHODS: We perfused normal rat livers at various portal flow rates (24, 30, and 36 ml/min) with 200 µM Gd-BOPTA and measured sinusoidal clearances, hepatocyte clearances, and hepatocyte concentrations of Gd-BOPTA. RESULTS: We showed that varying portal flow rates changes the sinusoidal clearance of Gd-BOPTA despite its low extraction ratio. Portal flow rates do not modify Gd-BOPTA clearance from hepatocytes into bile canaliculi but can change hepatocyte clearance back to sinusoids. CONCLUSION: At a given perfused concentration, portal flow rates modify Gd-BOPTA hepatocyte concentrations, a result important to consider when interpreting liver imaging.

Hepatocyte Concentrations of Indocyanine Green Reflect Transfer Rates Across Membrane Transporters.

Perioperative imaging with indocyanine green (ICG) is developing to increase safety in dissecting anatomical structures during hepatobiliary surgery. Images obtained with the fluorescence camera rely on concentrations measured in liver regions of interest. However, how ICG sinusoidal uptake and hepatocyte elimination rates generate ICG hepatocyte concentrations is largely unknown. To investigate such issue and better understand the role of membrane transporters in generating ICG hepatocyte concentrations, we perfused ICG in livers isolated from normal livers. Whether the well-known transporter inhibitor rifampicin modifies hepatocyte ICG concentrations was also studied. The dye has a very high and constant extraction ratio (96%) into hepatocytes. This persistent high extraction ratio generates a huge uphill concentration gradient across the sinusoidal membrane: from 5 µM (sinusoids) to 1600 µM (liver). When inside hepatocytes, ICG has low hepatocyte elimination (7 nmol/min.) and liver concentrations do not decrease much over time. Moreover, the tiny hepatocyte ICG efflux is mainly due to ICG return back to sinusoids (90%). Rifampicin slightly inhibits ICG uptake into hepatocytes and when inside hepatocytes blocks ICG efflux into bile canaliculi. In contrast, it increases ICG efflux back to sinusoids with significant decrease in ICG liver concentrations. Imaging with ICG in the perioperative period reflects the high hepatocyte concentrations and relies on the high extraction ratio across hepatocyte sinusoidal membrane. Although ICG concentrations are low in bile ducts, they are adequate for a good visualization and avoid bile duct injury.

Insights into the diagnosis of hepatocellular carcinomas with hepatobiliary MRI.

The incidence of hepatocellular carcinomas (HCCs) has increased worldwide in line with an improved screening by high-resolution imaging of cirrhotic livers. Besides abdominal ultrasonography and computerised tomography, magnetic resonance imaging (MRI) is an important tool to detect HCCs. With commercialisation of MR hepatobiliary contrast agents that cross membrane transporters in hepatocytes or tumour cells, MRI adds new information to detect and characterise HCCs. When tumour cells lose organic anion transporting polypeptides (OATP1B1/B3) in cell membranes facing sinusoidal blood, tumours appear hypointense (decreased contrast agent concentrations) in comparison to surrounding normal or cirrhotic liver that retains OATP1B1/B3 expression. However, expression, regulation, and prognostic significance of transporter evolution along carcinogenesis are not completely known. Moreover, understanding signal intensities in focal lesions also relies on transport functions of cellular efflux transporters. This manuscript reviews all the publications that associate liver imaging with hepatobiliary contrast agents and expression of transporters. The regulation of transporters along carcinogenesis to anticipate the prognosis of focal lesions is also included.

Advanced fibrosis: Correlation between pharmacokinetic parameters at dynamic gadoxetate-enhanced MR imaging and hepatocyte organic anion transporter expression in rat liver.

PURPOSE: To compare the value of enhancement and pharmacokinetic parameters measured at dynamic gadoxetate-enhanced magnetic resonance (MR) imaging in determining hepatic organic anion transporter expression in control rats and rats with advanced liver fibrosis. MATERIALS AND METHODS: Institutional animal review board approval was received before the study began. Advanced liver fibrosis was created in rats by means of carbon tetrachloride injections over an 8-week period. In 17 rats with liver fibrosis and eight control rats, dynamic gadoxetate-enhanced MR images of the liver were obtained during 1 hour after injection of 0.025 mmol gadoxetate per kilogram of body weight. Enhancement parameters (maximum enhancement [Emax], time to peak [Tmax], and elimination half-life) were measured on enhancement-versus-time curves, and pharmacokinetic parameters (hepatic extraction fraction [HEF] and mean residence time [MRT]) were obtained by means of deconvolution analysis of the concentration-versus-time curves in the liver and the portal vein. The parameters were correlated at simple and multiple regression analysis with the expression of the hepatic anion uptake transporter organic anion-transporting polypeptide 1A1 (Oatp1a1), the hepatobiliary transporter multidrug resistance-associated protein 2 (Mrp2), and the backflux transporter Mrp4, as determined with reverse transcription polymerase chain reaction. RESULTS: In rats with advanced liver fibrosis, the Emax, Tmax, HEF, and MRT decreased significantly relative to those in control rats, whereas the elimination half-life increased significantly. The enhancement and pharmacokinetic parameters correlated significantly with the expression of the transporters at simple regression analysis. At multiple regression analysis, HEF was the only parameter that was significantly associated with the expression of Oatp1a1 and Mrp2 (P < .001, r = 0.74 and P < .001, r = 0.70, respectively). CONCLUSION: The pharmacokinetic parameter HEF at dynamic gadoxetate-enhanced MR imaging is independently correlated with hepatic organic anion transporter expression.

The role of organic anion transporters in diagnosing liver diseases by magnetic resonance imaging.

The expression and transport functions of organic anion transporters are modified in liver diseases, and therefore the vascular clearances of endogenous and exogenous organic anions that are taken up by these transporters have been used to assess liver diseases in patients. More recently, liver imaging with hepatobiliary contrast agents, tracers, and dyes that cross hepatocytes through the organic anion transporting polypeptides (OATPs)-multidrug resistance-associated proteins (MRPs) pathway were developed to detect and characterize focal lesions and to assess the severity of diffuse liver diseases. This review focuses mainly on magnetic resonance imaging and highlights the growing interest in imaging the OATPs-MRP2 pathway to better understand liver diseases. Imaging provides noninvasive measurements of tissue concentrations that result from the interplay between influx and efflux membrane transport systems in normal or injured hepatocytes. Imaging with magnetic resonance hepatobiliary contrast agents improves the detection and the characterization of hepatic focal lesions. New developments of imaging to assess liver function and understand the hepatocellular concentrations of contrast agents are discussed.

Evidence of drug-drug interactions through uptake and efflux transport systems in rat hepatocytes: implications for cellular concentrations of competing drugs.

For drugs with hepatobiliary transport across hepatocytes, the interplay between uptake and efflux transporters determines hepatic concentrations of drugs, but the evolution over time of these concentrations is difficult to measure in humans other than with magnetic resonance imaging contrast agents in the liver. Gadobenate dimeglumine (BOPTA) is a contrast agent used in liver magnetic resonance imaging that enters into human hepatocytes through organic anion transporting polypeptides (OATP) and exits unchanged into bile through the multiple resistance-associated protein 2 (MRP2). Rifampicin (RIF) is transported by the same membrane proteins and may compete with BOPTA for hepatic uptake. Simultaneous drug-drug interactions through uptake and efflux transport systems in hepatocytes according to the cellular concentrations of competing drugs were never investigated. In perfused rat liver preparations, we demonstrate how the drug-drug interactions through transporters determine cellular concentrations of the competing drugs BOPTA and RIF, and we show that the cellular concentrations by modulating transport through membranes regulate the rat Oatp-Mrp2 interplay. Moreover, drug interactions through transporters change greatly over time.

Time-course proteomic analysis of taurocholate-induced necrotizing acute pancreatitis.

Acute pancreatitis is an inflammatory disease of the pancreas, which varies greatly in course and severity. Severe forms are associated with serious local and/or systemic complications, and eventually death. The pathobiology of acute pancreatitis is complex. Animal models have been developed to investigate pathobiological processes and identify factors determining disease course. We performed a time-course proteomic analysis using a rat model of severe necrotizing acute pancreatitis induced by taurocholate perfusion in the pancreatic ducts. Results showed that levels of proteins associated to a given biological process changed in a coordinated fashion after disease onset. It was possible to follow the response of a particular pathobiological process to pancreatitis induction and to compare the course of protein pathways. Proteins involved in acinar cell secretion were found to follow a different kinetics than other cellular processes. After an initial decrease, secretory pathway-associated proteins raised again at 18 h post-induction. This phenomenon coincided with a burst in the expression of pancreatitis-associated protein (REG3A), an acute phase protein produced by the exocrine pancreas, and with the decrease of classical markers of pancreatic injury, suggesting that the expression of proteins associated to the secretory pathway may be a modulating factor of pancreas injury. BIOLOGICAL SIGNIFICANCE: Acute pancreatitis (AP) is a complex inflammatory disease, the pathobiology of which is not yet fully understood. Various animal models, relying on different mechanisms of disease induction, have been developed in order to investigate pathobiological processes of AP. In this study, we performed a time-course proteomic analysis to investigate changes of the pancreas proteome occurring in an experimental model of AP induced by perfusion of taurocholate, a bile acid, into the pancreatic duct. This experimental model is characterized by a severe disease with pancreatic necrosis and systemic inflammation. The objectives of this study were to determine the kinetics of functionally related proteins in the early steps of the experimental disease in order to identify protein pathways playing key roles in AP pathobiology and to correlate these data with parameters classically used to assess disease severity. The present work provides for the first time an overview of protein expression in the pancreas during the course of taurocholate-induced necrotizing AP. We believe that correlation of these results with data obtained using proteomic or biochemical approaches in various experimental models of AP will help in highlighting new features, generating hypotheses and constitute therefore a strong and reliable basis for further targeted investigations.

Primovist, Eovist: what to expect?

Gadolinium ethoxybenzyl dimeglumine (Gd-EOB-DTPA, Primovist in Europe and Eovist in the USA) is a liver-specific magnetic resonance imaging contrast agent that has up to 50% hepatobiliary excretion in the normal liver. After intravenous injection, Gd-EOB-DTPA distributes into the vascular and extravascular spaces during the arterial, portal venous and late dynamic phases, and progressively into the hepatocytes and bile ducts during the hepatobiliary phase. The hepatocyte uptake of Gd-EOB-DTPA mainly occurs via the organic anion transporter polypeptides OATP1B1 and B3 located at the sinusoidal membrane and biliary excretion via the multidrug resistance-associated proteins MRP2 at the canalicular membrane. Because of these characteristics, Gd-EOB-DTPA behaves similarly to non-specific gadolinium chelates during the dynamic phases, and adds substantial information during the hepatobiliary phase, improving the detection and characterization of focal liver lesions and diffuse liver disease. This information is particularly relevant for the detection of metastases, and for the detection and characterization of nodular lesions in liver cirrhosis, including early hepatocellular carcinomas. Finally, GD-EOB-DTPA-enhanced magnetic resonance imaging may provide quantitative assessment regarding liver perfusion and hepatocyte function in diffuse liver diseases. The full potential of GD-EOB-DTPA-enhanced magnetic resonance imaging has to be established further. It is already clear that GD-EOB-DTPA-enhanced magnetic resonance imaging provides anatomic and functional information in the setting of focal and diffuse liver disease that is unattainable with magnetic resonance imaging enhanced with non-specific contrast agents.

How organic anions accumulate in hepatocytes lacking Mrp2: evidence in rat liver.

In the liver, the accumulation of hepatobiliary contrast agents is a crucial issue to understand the images of liver scintigraphy or magnetic resonance (MR) imaging. Thus, depending on the regulation of uptake and exit membrane systems in normal and injured hepatocytes, these contrast agents will accumulate differently within cells. Gadobenate dimeglumine (Gd-BOPTA) is a hepatobiliary MR contrast agent that distributes to the extracellular space and enters into rat hepatocytes through the sinusoidal transporters, organic anion-transporting polypeptides. Gd-BOPTA is not metabolized during its transport to the canalicular membrane where it is excreted into bile through multiple resistance protein-2 (Mrp2). It is not well known how Gd-BOPTA accumulates in normal livers and in livers lacking Mrp2. We perfused livers from normal rats and from rats lacking Mrp2 with (153)Gd-BOPTA at increasing concentrations and assessed the hepatic accumulation of this agent using a gamma probe placed above the livers. By use of a pharmacokinetic model that best described the amounts of Gd-BOPTA in perfusate, bile, and hepatic tissue over time, we showed how increasing concentrations and the absence of Mrp2 modify the hepatic accumulation of the contrast agent. It is noteworthy that despite the absence of Gd-BOPTA bile excretion and a similar efflux back to sinusoids in livers lacking Mrp2, the maximal hepatic accumulation of contrast agent was similar to normal rats. We also showed how hepatic accumulation relies on the concomitant entry into and exit from hepatocytes. Such information improves our understanding of liver imaging associated with the perfusion of hepatobiliary contrast agents, which was recently introduced in clinical practice.

Analysis of the pancreatic low molecular weight proteome in an animal model of acute pancreatitis.

We used a peptidomic approach for the analysis of the low molecular weight proteome in rat pancreatic tissue extracts. The goal was to develop a method that allows identifying endogenous peptides produced in the pancreas in the course of acute pancreatitis. The workflow combines peptides enrichment by centrifugal ultrafiltration, fractionation by isoelectric focusing, and LC-MS/MS analysis without prior enzymatic digestion. The method was assessed on pancreatic extracts from 3 rats with caerulein-induced pancreatitis and 3 healthy controls. A qualitative analysis of the peptide patterns obtained from the different samples was performed to determine the main biological processes associated to the identified peptides. Comparison of peptidomic and immunoblot data for alpha-tubulin, beta-tubulin and coatomer gamma showed that the correlation between the number of identified peptides and the protein abundance was variable. Nevertheless, peptidomic analysis highlighted inflammatory and stress proteins, which peptide pattern was related to acute pancreatitis pathobiology. For these proteins, the higher number of peptides in pancreatitis samples reflected an increase in protein abundance. Moreover, for murinoglobulin-1 or carboxypeptidase B, peptide pattern could be related to protein function. These data suggest that peptidomic analysis is a complementary approach to proteomics for investigating pathobiological processes involved in acute pancreatitis.

Delayed production of IL-18 in lungs and pancreas of rats with acute pancreatitis.

BACKGROUND/AIMS: During acute pancreatitis, tumor necrosis factor (TNF)-α, interleukin (IL)-1 and IL-6 play a pivotal role in promoting injury in the pancreas and remote organs. IL- 18 is a more recently discovered proinflammatory cytokine whose expression is also increased in serum. However, the profile of IL-18 expression in the pancreas and lung is unknown, and the aim of our study was to investigate such expression in rats with pancreatitis. METHODS: Acute pancreatitis was induced by taurocholic acid and endotoxin. Pulmonary and pancreatic injury was measured by biological and histological parameters. Lung injury was also evaluated in ex vivo lung preparations. RESULTS: Pancreatic and pulmonary injury appeared within 2 h after pancreatitis induction and persisted until the end of the protocol (18 h). TNF-α, IL-1 and IL-6 expression increased early in the lungs and pancreas, with a partial recovery by the end of the study. In contrast, IL-18 increased mostly by the end of the protocol (18 h after pancreatitis induction). CONCLUSION: IL-18 may serve as an additional marker to monitor the severity of inflammation during pancreatitis since its tissue production is delayed and appears after that of more commonly investigated cytokines. and IAP.

Hepatic regeneration is decreased in a rat model of sinusoidal obstruction syndrome.

BACKGROUND AND OBJECTIVES: Oxaliplatin is a chemotherapeutic drug for colorectal adenocarcinoma able to extend the indications for resection of colorectal liver metastases. However, the drug may severely injure hepatic sinusoids, inducing a sinusoidal obstruction syndrome in non-tumoral parenchyma with a risk of decreased regeneration in the remnant liver following partial hepatectomy. METHODS: We then investigated the evolution of hepatic functions and liver regeneration following partial hepatectomy in rats with sinusoidal obstruction syndrome. The sinusoidal obstruction syndrome was induced with a single intragastric administration of monocrotaline (MCT). RESULTS: MCT administration induced obstruction of the hepatic microcirculation and increased portal pressure, hepatic VEGF expression, and Ki67 positive hepatocytes. A mild cholestasis was present without modification of hepatic tests. Following a 70% hepatectomy, liver regeneration was significantly impaired by MCT administration and this impaired regeneration was associated with hepatocellular injury evidenced 1 week after hepatectomy. CONCLUSIONS: The presence of sinusoidal obstruction syndrome impairs hepatic regeneration in this rat model of sinusoidal obstruction syndrome.

Proteomic profiling in an animal model of acute pancreatitis.

Acute pancreatitis (AP) is an inflammatory disease of the pancreas, which evolves in approximately 20% of the patients to a severe illness associated with a high mortality rate. In this study, we performed a comparative proteomic analysis of pancreatic tissue extracts from rats with AP and healthy rodent controls in order to identify changes in protein expression related to the pathobiological processes of this disease. Pancreatic extracts from diseased and controls rats were analyzed by 2-DE and MS/MS. A total of 125 proteins were identified from both samples. Comparative analysis allowed the detection of 42 proteins or protein fragments differentially expressed between diseased and control pancreas, some of them being newly described in AP. Interestingly, these changes were representative of the main pathobiological pathways involved in this disease. We observed activation of digestive proteases and increased expression of various inflammatory markers, including several members of the alpha-macroglobulin family. We also detected changes related to oxidative and cell stress responses. Finally, we highlighted modifications of 14-3-3 proteins that could be related to apoptosis regulation. These results showed the interest of proteomic analysis to identify changes characterizing pancreatic tissue damage and, therefore, to highlight new potential biomarkers of AP.

Improved visualization of vessels and hepatic tumors by micro-computed tomography (CT) using iodinated liposomes.

OBJECTIVE: The goal of this study was to determine whether iodinated liposomes are a suitable tracer for mice microvessel and liver imaging by preclinical computed tomography (CT). MATERIALS AND METHODS: Iodinated liposomes were evaluated for vessel and liver imaging. A first group of nude mice was imaged by micro-CT after i.v. injection of liposomes at 1 or 2 gI/kg body weight (b.w.) for intervals up to 24 hours. A second group of mice bearing liver micrometastases was imaged after injection of liposomes at 2 gI/kg b.w. for intervals up to 24 hours. RESULTS: Vascular enhancements of 120 +/- 8 and 322 +/- 20 Hounsfield unit (HU) were obtained after injection of liposomes at 1 or 2 gI/kg b.w., respectively. This enhancement decreased with a blood half-life of 135 +/- 10 and 86 +/- 9 minutes, respectively. Liver enhancement of 157 +/- 5 and 235 +/- 23 HU were obtained after injection of iodinated liposomes at 1 and 2 gI/kg b.w., respectively. Liver micrometastases (250 microm) were detectable after injection of iodinated liposomes at 2 gI/kg b.w. CONCLUSIONS: Iodinated liposomes are a suitable contrast agent for vessels and liver imaging by micro-CT allowing clear vascular enhancement and detection of small liver metastases.