Catherine M. Pastor

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.

Hepatopulmonary syndrome increases the postoperative mortality rate following liver transplantation: a prospective study in 90 patients.

Hepatopulmonary syndrome (HPS) is a frequent pulmonary complication of patients with end‐stage liver diseases. HPS is diagnosed by hypoxemia and pulmonary vascular dilatation and is an independent risk factor of mortality. Orthotopic liver transplantation (OLT) is the only factor that modifies the natural course of HPS. Once patients with HPS have been transplanted, their long‐term survival rate is similar to transplanted patients without HPS. Consequently, HPS is an indication of OLT whatever the severity of hypoxemia. However, besides the favorable long‐term survival of HPS patients with OLT, a high postoperative mortality (mostly within 6 months) has been suggested. The aim of our study was to analyze the incidence of HPS and postoperative outcome after OLT in 90 consecutive patients. All patients were prospectively included and had blood gas analysis to detect HPS. Patients with hypoxemia had contrast echocardiography to confirm HPS. Nine patients had HPS with a 50 ≤ PaO2≤ 70 mmHg. Among them 3 (33%) died while the mortality rate was 9.2% in the group without HPS (7 over 76 patients). In the HPS patients who survived, the syndrome completely recovered within 6 months. In conclusion, our study shows a high postoperative mortality rate following OLT even though the preoperative PaO2 was >50 mmHg in all HPS patients transplanted.

Effects of L-arginine and L-nitro-arginine treatment on blood pressure and cardiac output in a rabbit endotoxin shock model

ObjectiveTo verify the effect of nitric oxide system modification during sepsis, not only in terms of pressure but also in terms of perfusion flow. DesignExperimental, comparative study. SettingLaboratory of a university hospital. SubjectsTwenty-six New Zealand male rabbits (2 to 2.5 kg body weight) were studied under anesthesia. InterventionsNitric oxide pathways were modified during shock-induced hypotension, using L-arginine (600 mg/kg) and L-nitro-arginine (7.5 mg/kg), which were infused 75 mins after endotoxin injection. Measurements and Main ResultsMean arterial pressure (MAP) and cardiac output, as well as ascending aortic velocity, were measured and aortic conductance (aortic velocity/MAP in cm/ sec/mm Hg) was calculated. Both L-arginine and L-nitro-arginine increased MAP to the pre-endotoxin level, but only L-arginine increased aortic velocity in association with a marked increase in aortic conductance (p < .001). L-nitroarginine significantly (p < .05) decreased aortic velocity as compared with the control endotoxin group, with an intense vasoconstriction as shown by a significant (p < .001) decrease in aortic conductance. ConclusionsThese results, along with the high mortality rate in the L-nitro-arginine treated group, challenge the hypothesis that nitric oxide release inhibition has a beneficial effect in septic shock. (Crit Care Med 1994; 22:465–469)

Magnetic resonance imaging with hepatospecific contrast agents in cirrhotic rat livers

Objective:During biliary cirrhosis in rats, organic anion-transporting peptides (Oatps) and ATP-dependent multidrug resistance-associated protein 2 (Mrp2) that are likely to transport the contrast agent Gd-BOPTA through hepatocytes are down-regulated. However, the consequences of such down-regulation on the signal intensity (SI) enhancement are unknown. Consequently, the aim of our study was to measure the hepatic SI enhancement during Gd-BOPTA perfusion as well as the Oatp and Mrp2 expression in normal and cirrhotic livers. Materials and Methods:The hepatic SI enhancement during Gd-BOPTA perfusion was measured in livers isolated from normal rats and rats that had a bile duct ligation (BDL) 15, 30, and 60 days before the perfusion. Hepatic injury and transporter expression were measured in control and cirrhotic rats. Results:BDL induced a severe hepatic injury that increased over time with a down-regulation of the transporter expression. The extracellular space (assessed by Gd-DTPA perfusion) increased with the severity of the disease. Gd-BOPTA-induced SI enhancement remained similar in BDL-15 and BDL-30 rats than in control rats but significantly decreased in severe cirrhosis (BDL-60 rats). In comparison, the Mn-DPDP-induced SI enhancement decreases proportionally to the severity of the disease. Conclusion:During biliary cirrhosis, Gd-BOPTA-induced SI enhancement could not be related to the hepatic expression of transporters.

Role of Macrophage Inflammatory Peptide-2 in Cerulein-Induced Acute Pancreatitis and Pancreatitis-Associated Lung Injury

Acute pancreatitis is an inflammatory process of variable severity, and leukocytes are thought to play a key role in the development of pancreatitis and pancreatitis-associated lung injury. The effects of mediators released by these inflammatory cells may induce tissue damage. The aim of our study was to evaluate the role of the chemokine, macrophage inflammatory protein-2 (MIP-2), in the pathogenesis of cerulein-induced pancreatitis and pancreatitis-associated lung injury. The severity of pancreatitis was measured by serum amylase, pancreatic edema, acinar cell necrosis, and myeloperoxidase activity. Lung injury was quantitated by evaluating lung microvascular permeability and lung myeloperoxidase activity. To determine the role of MIP-2 in the pathophysiology of the disease, anti-MIP-2 antibody was administered either 1 hour before or 2 hours after the start of cerulein administration. MIP-2 concentrations increased in serum, pancreas, and lung tissues in mice treated with cerulein. Anti-MIP-2 antibody administrated either before or after cerulein partially protected against pancreas and lung injury. These results show that MIP-2 plays a key role in the pathophysiology of acute pancreatitis and that MIP-2 blockade may improve the outcome of the disease.

Function of both sinusoidal and canalicular transporters controls the concentration of organic anions within hepatocytes

We hypothesized that the function of both sinusoidal and canalicular transporters importantly controls the concentrations of organic anions within normal hepatocytes. Consequently, we investigated how acute transport regulation of the sinusoidal organic anion transporting polypeptides (Oatps) and the canalicular multidrug resistance associated protein 2 (Mrp2) determines the hepatic concentrations of the organic anion gadolinium benzyloxypropionictetraacetate (BOPTA) in rat livers. Livers were perfused with labeled BOPTA in different experimental settings that modify the function of Oatps and Mrp2 through the protein kinase C (PKC) pathway. Intrahepatic concentrations were continuously measured with a gamma probe placed above rat livers. Labeled BOPTA was also measured in perfusate and bile. We showed that when the function of Oatps and Mrp2 is modified in such a way that BOPTA entry and exit are similarly decreased, concentrations of organic anions within hepatocytes remain unaltered. When exit through Mrp2 is abolished, hepatic concentrations are high if entry through Oatps is only slightly decreased (livers without Mrp2 expression) or low if BOPTA uptake is more importantly decreased (livers perfused with a PKC activator). These results highlight that the function of both sinusoidal and canalicular transporters is important to determine the concentration of organic anions within hepatocytes.

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 &mgr;m) 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.

Effects of abdominal CO2 insufflation and changes of position on hepatic blood flow in anesthetized pigs

During surgical laparoscopy, total hepatic blood flow (THBF) may be modified by CO2 insufflation, changes of tilt, ventilation with high tidal volume, hypercapnia, and anesthesia, but little information is available on the THBF during the procedure. To investigate the changes of hepatic blood flow following the combination of abdominal CO2 insufflation and changes of tilt, we measured mean arterial pressure (MAP), cardiac output, portal vein blood flow (PVBF), and hepatic artery blood flow (HABF) in anesthetized and ventilated pigs. CO2 was insufflated in the abdomen [intra-abdominal pressure (IAP) approximately 15 mmHg], and the hepatic blood flow was measured in various positions (horizontal, 10 degrees and 20 degrees head down, and 10 degrees and 20 degrees head up) before and during CO2 insufflation. CO2 insufflation in the horizontal position did not modify MAP, cardiac output, or PVBF but increased HABF. The head-up tilt decreased MAP, cardiac output, and both hepatic flows in the absence of pneumoperitoneum, but in the presence of abdominal CO2 only cardiac output and PVBF were decreased. The head-down tilt increased MAP and THBF in the absence of pneumoperitoneum, whereas no change was observed in the presence of abdominal CO2. The combination of CO2 insufflation and changes of tilt was not deleterious to hepatic perfusion. These results suggest that hepatic blood flow may be preserved during surgical laparoscopy if the tilt does not exceed 20 degrees and if IAP after CO2 insufflation remains <15 mmHg.During surgical laparoscopy, total hepatic blood flow (THBF) may be modified by CO2insufflation, changes of tilt, ventilation with high tidal volume, hypercapnia, and anesthesia, but little information is available on the THBF during the procedure. To investigate the changes of hepatic blood flow following the combination of abdominal CO2 insufflation and changes of tilt, we measured mean arterial pressure (MAP), cardiac output, portal vein blood flow (PVBF), and hepatic artery blood flow (HABF) in anesthetized and ventilated pigs. CO2 was insufflated in the abdomen [intra-abdominal pressure (IAP) ∼15 mmHg], and the hepatic blood flow was measured in various positions (horizontal, 10° and 20° head down, and 10° and 20° head up) before and during CO2 insufflation. CO2 insufflation in the horizontal position did not modify MAP, cardiac output, or PVBF but increased HABF. The head-up tilt decreased MAP, cardiac output, and both hepatic flows in the absence of pneumoperitoneum, but in the presence of abdominal CO2 only cardiac output and PVBF were decreased. The head-down tilt increased MAP and THBF in the absence of pneumoperitoneum, whereas no change was observed in the presence of abdominal CO2. The combination of CO2 insufflation and changes of tilt was not deleterious to hepatic perfusion. These results suggest that hepatic blood flow may be preserved during surgical laparoscopy if the tilt does not exceed 20° and if IAP after CO2 insufflation remains <15 mmHg.

The role of junctional adhesion molecule C (JAM-C) in acute pancreatitis.

The recruitment of inflammatory cells contributes significantly to tissue injury in acute pancreatitis. This process implies several molecular interactions between circulating and endothelial cells. The adhesion molecule junctional adhesion molecule C (JAM‐C) is involved in leukocyte transendothelial migration and it can form homophilic (JAM‐C/JAM‐C) and heterophilic interactions with the leukocyte integrin αMβ2. In this study, the effect of early administration of monoclonal antibodies directed against JAM‐C in cerulein‐induced acute pancreatitis was assessed. This reagent significantly blocked influx of leukocytes, release of serum amylase, secretion of inflammatory cytokines, and acinar cell necrosis. These effects were rapid and protected against tissue injury throughout the duration of the model. Conversely, cerulein‐induced acute pancreatitis was more severe in transgenic mice overexpressing JAM‐C on endothelial cells under the control of the Tie2 promoter. It is proposed that JAM‐C expressed by endothelial cells contributes to the pathophysiology of acute pancreatitis and could be considered a target for clinical applications. Copyright

Natural history of long-term lung injury in mouse experimental pancreatitis

Objective In patients suffering from acute pancreatitis, the pathogenesis of pancreatitis-associated lung injury is not completely understood. Several rodent models of pancreatitis-associated lung injury suggested that activated neutrophils and the release of proinflammatory mediators after the activation of inflammatory cells within the pancreas might play an important role in translating the pancreatic inflammation to the lungs. In this study, we examined the natural history of pancreatitis-associated lung injury during an entire week. Subjects Mice were administered 12 hourly intraperitoneal injections of a supramaximal dose of cerulein. Measurements and Main Results The severity of pancreatitis was time-dependent, with a maximal injury by 12–24 hrs after the start of cerulein administration. Pancreatitis was associated with a significant lung injury characterized by a rise in lung microvascular permeability, sequestration of neutrophils within the lungs, and a marked thickening of alveolar membranes. Within the lungs, the peak of macrophage inflammatory peptide-2, which attracts inflammatory cells within the injured area, preceded the peaks of both tumor necrosis factor-&agr; and intercellular adhesion molecule-1. Moreover, histologic injury peaked by 12 hrs, with a full recovery at day 7. Serum macrophage inflammatory peptide-2 concentrations were significantly correlated with the occurrence of pulmonary leakage. Lung macrophage inflammatory peptide-2 concentrations peaked 12 hrs before pancreatic concentrations. Conclusions Mediators released by the pancreas into the blood during acute pancreatitis induce within the lungs the chronological expression of macrophage inflammatory peptide-2, tumor necrosis factor-&agr;, and intercellular adhesion molecule-1.