Honoring the contract with our patients: outcome after repeated re-transplantation of the liver.

The aim of this study was to describe the outcome after repeated orthotopic liver re-transplantations (re-OLT) in a population of adults and children, and to determine whether such repeated re-transplantations are an effective treatment or should be considered futile. In a consecutive series of 867 patients, 628 adults and 239 children, who underwent OLT at the University Medical Center Groningen, 23 patients (2.7%), 10 adults and 13 children, underwent more than two re-transplantations of the liver between March 1979 and October 2008. All 23 patients had a second re-transplantation, and seven of them received a third transplant. The overall actuarial patient survival at 1, 5, and 10 yr after primary OLT was 96%, 87%, and 71%, respectively. The overall actuarial patient survival after the second re-OLT was 78%, 73%, and 67%, respectively. Sixteen patients (70%) survived long term. However, for the 23 repeated re-transplantation patients, 76 grafts were used. In a simulation calculation, it was shown that honoring the initial commitment to the 23 patients ultimately led to more surviving patients and less death than if treatment of the original patients was stopped after the first re-transplantation and the remaining grafts were allocated to other primary graft recipients.

The evolution of surgical techniques in clinical liver transplantation. A review.

Currently, liver transplantation (LT) is an accepted method of treatment of end-stage liver disease, metabolic diseases with their primary defect in the liver and unresectable primary liver tumors. Surgical techniques in LT have evolved considerably over the past 40 yr. The developments have led to a safer procedure for the recipient reflected by continuously improving survival figures after LT. Also the new techniques offer the possibility of tailoring the operation to the needs and condition of the recipient as in partial grafting or in different revascularization techniques, or in techniques of biliary reconstructions. In addition, the new techniques such as split LT, domino transplantation and living donor LT have brought about an increase in the available grafts. In this review the evolution of surgical techniques in LT over the past 40 yr and their contribution to the current results are discussed.

Liver transplantation in patients with hepatocellular carcinoma.

Liver transplantation has a definitive place in the treatment of patients with hepatocellular carcinoma (HCC) in a cirrhotic liver. Patients with a tumor load within the Milan criteria have excellent survival comparable to survival in patients with benign indications. When tumor load exceeds the Milan criteria survival decreases. Staging of patients with HCC in a cirrhotic liver is deficient due to the restrictions of the current imaging modalities. The exact place of tumor controlling therapies during the waiting time for transplantation is not yet clear. No evidence of sufficient level is available as to the efficacy of pre-, per- or postoperative chemotherapy. Promising new drugs are currently tested. This counts also for the use of new immunosuppressant with concomitant tumor suppressive capabilities.

The survival paradox of elderly patients after major liver resections.

OBJECTIVE: The objective of this study is to assess the outcome of liver resections in the elderly in a matched control analysis. PATIENTS AND METHODS: From a prospective single center database of 628 patients, 132 patients were aged 60 years or over and underwent a primary major liver resection. Of these patients, 93 could be matched one-to-one with a control patient, aged less than 60 years, with the same diagnosis and the same type of liver resection. The mean age difference was 16.7 years. RESULTS: Patients over 60 years of age had a significantly higher American Society of Anaesthesiologists (ASA) grade. All other demographics and operative characteristics were not different. In-hospital mortality and morbidity were higher in the patients over 60 years of age (11% versus 2%, p = 0.017 and 47% versus 31%, p = 0.024). One-, 3-, and 5-year survival rates in the patients over 60 years of age were 81%, 58%, and 42%, respectively, compared to 90%, 59%, and 42% in the control patients (p = 0.558). Unified model Cox regression analysis showed that resection margin status (hazard ratio 2.51) and ASA grade (hazard ratio 2.26), and not age, were determining factors for survival. CONCLUSION: This finding underlines the important fact that in patient selection for major liver resections, ASA grade is more important than patient age.

Results of pancreaticoduodenectomy in patients with periampullary adenocarcinoma: perineural growth more important prognostic factor than tumor localization.

OBJECTIVE: To study the impact of perineural growth as a prognostic factor in periampullary adenocarcinoma (pancreatic head, ampulla of Vater, distal bile duct, and duodenal carcinoma). SUMMARY BACKGROUND DATA: Pancreatic head carcinoma is considered to have the worst prognosis of the periampullary carcinomas. Several other prognostic factors for periampullary tumors have been identified, eg, lymph node status, free resection margins, tumor size and differentiation, and vascular invasion. The impact of perineural growth as a prognostic factor in relation to the site of origin of periampullary carcinomas is unknown. METHODS: Data of 205 patients with periampullary carcinomas were retrieved from our prospective database. Pancreaticoduodenectomy was performed in 121 patients. Their clinicopathological data were reviewed and analyzed in a multivariate analysis. RESULTS: Perineural growth was present in 49% of the cases (37 of the 51 patients with pancreatic head carcinoma; 7 of the 30 patients with ampulla of Vater carcinoma; 7 of the 19 with distal bile duct carcinoma; and 8 of the 21 with duodenal carcinoma). Overall 5-year survival was 32.6% with a median survival of 20.7 months. Median survival in tumors with perineural growth was 13.1 months compared with 36.0 months in tumors without perineural growth (P < 0.0001) Using multivariate analysis, the following unfavorable prognostic factors were identified: perineural growth (RR = 2.90, 95% CI 1.62-5.22), nonradical resection (RR = 2.28, 95% CI 1.19-4.36), positive lymph nodes (RR = 1.96, 95% CI 1.11-3.45), and angioinvasion (RR = 1.79, 95% CI 1.05-3.06). Portal or superior mesenteric vein reconstruction and tumor localization were not of statistical significance. CONCLUSION: Perineural growth is a more important risk factor for survival than the primary site of periampullary carcinomas.

The outcome of primary liver transplantation from deceased donors in children with body weight < or =10 kg.

Between November 1982 and March 2006, 67 children with body weight < or =10 kg had a primary liver transplantation from deceased donors in our unit. The aim of this study was to analyze the outcome in terms of patient and graft survival and to search for factors affecting this outcome. Overall, one-, three-, five-, and 10-yr primary patient and graft survival rates were 73%, 71%, 66%, 63% and 59%, 56%, 53%, 48%, respectively. Twenty-four of 67 (36%) children died and in the remaining 22 (33%), the first grafts failed and they were retransplanted. Cox regression analysis revealed that a need for retransplantation and urgent transplantation were important predictors for patient survival (p = 0.04 and p = 0.001, respectively). To assess whether the need for retransplantation can be influenced, all study variables were compared between surviving grafts and failed grafts. Cox regression analysis showed that only donor/recipient (D/R) weight ratio proved to be independent predictor for graft survival (p = 0.004). After comparison of graft survival with the long rank test according to different D/R weight ratios (3.0-7.0), the cut-off point for significantly different graft survival approached 4.0. The one-, three-, five-, and 10-yr graft survival for technical variant grafts with a D/R weight ratio <4.0 was 85%, 68%, 68%, and 68% compared with a D/R weight ratio >4.0 was 44%, 38%, 38%, and 30%, respectively (p = 0.02). In summary, patient survival in children with body weight < or =10 kg is determined by urgent transplantation and the need for retransplantation. Graft loss and retransplantation in small children can be prevented by adequate size matching of donor and recipient whereby a D/R weight ratio <4.0 seems to offer the favorable outcome.

Vascular events after liver transplantation: a long-term follow-up study.

Long-term follow-up studies on the impact of vascular events (VE) and risk factors of liver transplant recipients are scarce. In this study, 311 recipients of a first isolated liver transplant who survived at least 1 year were followed up from 1979 to 2002. The median follow-up duration was 6.2 (range1-22.7) years. Overall median survival was 18.7 [95% confidence interval (CI): 15.5-20.1] years and this was significantly lower compared with age- and sex-matched controls. Eleven (21%) of the patients had a vascular cause of death and VE were the third cause of death. VE occurred later compared with other causes of death (mean 10.3 years vs. 4.5 years, P < 0.0001, 95% CI: 2.7-8.9). Systolic hypertension, systolic blood pressure, smoking, renal failure, age, hypertriglyceridemia, serum total cholesterol levels and hypercholesterolemia at the 1-year follow-up visit were associated with the occurrence of VE, but renal failure and age at 1 year after transplantation were the only independent risk factors for vascular death (hazard ratio 0.06, 95% CI: 0.01-0.41 and hazard ratio 1.17, 95% CI: 1.02-1.34, respectively). Finally, it was shown that the adequate treatment of hypertension was associated with a significant reduced risk of vascular death. Therefore, vascular risk factors should be treated aggressively to prevent VE in the long term.

Outcome and pattern of recurrence after curative resection for hepatocellular carcinoma in patients with a normal liver compared to patients with a diseased liver.

BACKGROUND/AIMS: The purpose of this study was to investigate whether differences existed in demography and outcome after resection for hepatocellular carcinoma (HCC) in patients with a normal liver compared to patients with a diseased liver. METHODOLOGY: Twenty-seven Caucasian patients with HCC in a histologically proven normal liver (NL group) in the Netherlands and 141 Asian patients with HCC in a diseased liver (DL group) in Japan underwent a curative liver resection. Patient and tumor characteristics, post-resectional disease-free, overall survival rates and pattern of recurrence were investigated. RESULTS: HCC's in the NL group were found to be larger, in a more advanced stage and needed more extended resections compared to HCC's in the DL group. Microvascular invasion was similar in both groups, while capsule formation was observed less in the NL group. Overall survival and disease-free survival after curative resection were not statistically different between both groups. Also even after stratification for T-stage, there was no difference in survival. Although the rate of recurrence was similar in both groups, a significantly higher number of extrahepatic metastases was observed in the NL group. CONCLUSIONS: Distinct demographic differences existed between patients with HCC in the NL group compared to patients in the DL group. Extrahepatic recurrences were more frequent after curative resection for HCC in a normal liver. No difference in survival was demonstrated between both groups.

Dynamics of the vascular profile of the finer branches of the biliary tree in normal and diseased human livers.

BACKGROUND/AIMS: Results of our previous studies supported the concept that in the human liver, the smallest ramification of the biliary tree, the bile ductules, might contain hepatic progenitor cells. An insufficient proliferative response and loss of bile ductules preceded bile duct loss whereas preservation of bile ductules mitigated bile duct loss. METHODS: Presently we investigated the vascular profile of the bile ductules in diseased human livers and livers showing normal histological features as controls, using CD34, CK7 and alphaSMA antibodies in a double immunolabeling technique. VEGF-A expression was also studied. In control livers bile ductules traversed the boundaries of the portal tract into the lobule as ductular-vascular units, in a pattern outlining the classic hexagonal lobule, following the vascular septa. The latter are thought to be extensions of portal veins. In diseased states the two structures reacted in unison. Increased or decreased numbers of ductules were consistently accompanied by similar changes of accompanying microvessels. Increased numbers of ductules and microvessels were paralleled by increased ductular expression of VEGF-A. RESULTS: Our data support the concept that the smallest branches of the biliary tree might have their own vascular supply and that the ductules might in turn maintain their vasculature during regenerative processes.

The finest branches of the biliary tree might induce biliary vascularization necessary for biliary regeneration.

BACKGROUND/AIMS: The finer branches of the biliary tree play an important role in biliary regeneration. They are consistently escorted by microvessels. Defects in the vascularization of these structures could impair bile duct regeneration. Therefore, we investigated the pattern of the escorting microvessels during the development of bile duct loss in the human liver, using chronic rejection as a model. METHODS: The number of interlobular bile ducts, bile ductules and extraportal biliary cells with and without escorting microvessels and the expression of VEGF-A were studied in follow-up biopsies of 12 patients with chronic rejection and 16 control patients with acute rejection without progression to chronic rejection. RESULTS: The controls showed a proliferation of bile ductules at 1-week and 1-month. Proliferation of bile ductules without microvessels preceded proliferation of bile ductules with microvessels. Proliferation of the microvascular compartment followed biliary proliferation. This sequence of events was not observed in the chronic rejection group, in which all biliary structures decreased in time. VEGF-A expression was increased at 1-week and 1-month in both groups. CONCLUSIONS: An immediate proliferative response of the finer branches of the biliary tree followed by proliferation of the microvascular compartment after biliary injury seems to be a prerequisite for bile duct regeneration.

The effect of HLA mismatches, shared cross-reactive antigen groups, and shared HLA-DR antigens on the outcome after pediatric liver transplantation.

The aim of this study was to analyze the effect of human leukocyte antigen (HLA) class I and HLA-DR mismatching, sharing cross-reactive antigen groups (CREGs), and sharing HLA-DR antigens on the outcome after pediatric liver transplantation. Outcome parameters were graft survival, acute rejection, and portal fibrosis. A distinction was made between full-size (FSLTx) and technical-variant liver transplantation (TVLTx). A total of 136 primary transplants were analyzed. The effect of HLA on the outcome parameters was analyzed by adjusted multivariate logistic and Cox regression analysis. HLA mismatches, shared CREGs, and shared HLA-DR antigens affected neither overall graft survival nor survival after FSLTx. Survival after TVLTx was superior in case of 2 mismatches at the HLA-DR locus compared to 0 or 1 mismatch (P = 0.01) and in case of no shared HLA-DR antigen compared to 1 shared HLA-DR antigen (P = 0.004). The incidence of acute rejection was not influenced by HLA. The incidence of portal fibrosis could be analyzed in 62 1-yr biopsies and was higher after TVLTx than FSLTx (P = 0.04). The incidence of portal fibrosis after TVLTx with 0 or 1 mismatch at the HLA-DR locus was 100% compared to 43% with 2 mismatches (P = 0.004). After multivariate analysis, matching for HLA-DR and matching for TVLTx were independent risk factors for portal fibrosis. In conclusion, an overall beneficial effect of HLA matching, sharing CREGs, or sharing HLA-DR antigens was not observed. A negative effect was present for HLA-DR matching and sharing HLA-DR antigens on survival after TVLTx. HLA-DR matching might be associated with portal fibrosis in these grafts.

Hepatic expression of ABC transporters G5 and G8 does not correlate with biliary cholesterol secretion in liver transplant patients.

The adenosine triphosphate (ATP)-binding cassette (ABC)-transporters ABCG5 and ABCG8 have been shown to mediate hepatic and intestinal excretion of cholesterol. In various (genetically modified) murine models, a strong relationship was found between hepatic expression of ABCG5/ABCG8 and biliary cholesterol content. Our study aimed to relate levels of hepatic expression of ABCG5 and ABCG8 to biliary excretion of cholesterol in man. From 24 patients who had received a liver transplant, bile samples were collected daily after transplantation over a 2-week period to determine biliary composition. Expression of ABCG5, ABCG8, MDR3, and BSEP was assessed by real-time polymerase chain reaction (PCR) in liver biopsy specimens collected before and after transplantation. Levels of hepatic ABCG5, ABCG8, and MDR3 messenger RNA (mRNA) were strongly correlated. After transplantation, the biliary secretion rate of cholesterol continuously increased, coinciding with gradual increases in bile salt and phospholipid secretion. In contrast, hepatic levels of ABCG5 and ABCG8 mRNA remained unchanged. Surprisingly, no correlation was found between the hepatic expression of ABCG5 and ABCG8 and rates of biliary cholesterol secretion, normalized for biliary phospholipid secretion. As expected, the concentration of biliary phospholipids correlated well with MDR3 expression. In conclusion, the strong relationship between ABCG5 and ABCG8 gene expression is consistent with the coordinate regulation of both genes, and in line with heterodimerization of both proteins into a functional transporter. Hepatic ABCG5/ABCG8 expression, at least during the early phase after transplantation, is not directly related to biliary cholesterol secretion in humans. This finding suggests the existence of alternative pathways for the hepatobiliary transport of cholesterol that are not controlled by ABCG5/ABCG8.

Minimizing blood loss in liver transplantation: progress through research and evolution of techniques.

Blood loss during liver transplantation has long been recognized as an important cause of morbidity and, especially in the early days, also mortality. It is well known that blood transfusions are associated with an increased risk of postoperative complications, such as infections, pulmonary complications, protracted recovery, and a higher rate of reoperations. Many studies have been performed during the past decades to elucidate the mechanisms of increased blood loss in liver transplantation. In the late 1980s, primary hyperfibrinolysis was identified as an important mechanism of bleeding during liver transplantation. This has provided the scientific basis for the use of antifibrinolytic drugs in liver transplant recipients. Several randomized, controlled studies have shown the efficacy of these compounds in reducing blood loss and transfusion requirements during liver transplantation. In addition, increasing experience and improvements in surgical technique, anesthesiological care and better graft preservation methods have contributed to a steady decrease in blood transfusion requirements in most liver transplant programs. Several centers are now reporting liver transplantation without any need for blood transfusion in up to 30% of their patients. Despite these improvements, most patients undergoing liver transplantation still require blood transfusions that have a negative impact on outcome, emphasizing the need for further attempts to control blood loss by surgeons and anesthesiologists. This paper provides an overview of the clinical and research developments, which have contributed to a reduction in blood loss and transfusion requirements, resulting in an important reduction in morbidity and mortality after liver transplantation during the last two decades.

Sequential and simultaneous revascularization in adult orthotopic piggyback liver transplantation.

The aim of the study was to assess whether there is a difference in outcome after sequential or simultaneous revascularization during orthotopic liver transplantation (OLT) in terms of patient and graft survival, mortality, morbidity, and liver function. The study population consisted of 102 adult patients with primary full-size piggyback OLT transplanted between January 1998 and December 2001. In 71 patients (70%) the grafts were sequentially reperfused after completion of the portal vein anastomosis and subsequent arterial reconstruction was performed (sequential reperfusion [SeqR] group). In 31 patients (30%) the graft was reperfused simultaneously via the portal vein and hepatic artery (simultaneous reperfusion [SimR] group). Patient and graft survival at 1, 3, and 6 months and at 1 year did not differ between the SeqR group and the SimR group. The red blood cell (RBC) requirements were significantly higher in the SimR group (5.5 units; range 0-20) in comparison to the SeqR group (2 units; range 0-19) (P = 0.02). Apart from a higher number of biliary anastomotic complications and abdominal bleeding complications in the SimR group in comparison to the SeqR group (13% vs. 2% and 19% vs. 6%, respectively; P = 0.06), morbidity was not different between the groups. No differences between the groups were observed regarding the incidence of primary nonfunction (PNF), intensive care unit stay, and acute rejection. This was also true for the severity of rejections. Postoperative recuperation of liver function was not different between the groups. In conclusion, no advantage of either of the 2 reperfusion protocols could be observed in this analysis, especially with respect to the incidence of ischemic type biliary lesions (ITBL).

P53 mutation analysis of colorectal liver metastases: relation to actual survival, angiogenic status, and p53 overexpression.

PURPOSE: To correlate TP53 mutations with angiogenic status of the tumor and prognosis after liver surgery in patients with colorectal liver metastases and to correlate immunohistochemical staining of p53 protein with TP53 gene mutations. EXPERIMENTAL DESIGN: Tumors of 44 patients with surgically treated colorectal liver metastases were analyzed for (a) TP53 mutations using denaturing gradient gel electrophoresis followed by sequencing, (b) microvessel density using the hot spot overlap technique, (c) apoptotic rate in tumor cells and endothelial cells of tumor microvessels using double immunostaining for anti-cleaved caspase 3 and anti-CD34, and (d) expression of p53 protein using immunohistochemistry. RESULTS: TP53 mutations were detected in 36% of the metastases and occurred more frequently in liver metastases from left-sided colon tumors than from right-sided colon tumors (P = 0.04). In metastases with TP53 mutations, microvessel density was higher compared with tumors with wild-type p53. Endothelial cell apoptosis was not different in tumor microvessels from TP53-mutated versus nonmutated tumors. The 5-year actual survival was not influenced by TP53 mutational status, microvessel density, or endothelial cell apoptotic rate of the tumors. Based on immunohistochemical p53 overexpression, the positive and negative predictive values of TP53 mutations were 61% and 82%. CONCLUSIONS: In patients with surgically treated colorectal liver metastases, TP53 mutations and angiogenic status did not influence prognosis. Immunohistochemistry is not a reliable technique for detecting TP53 mutations.

Extrahepatic bile duct resection in combination with liver resection for hilar cholangiocarcinoma: a report of 42 cases.

From September 1986 until December 2001, 42 patients (20 males and 22 females) underwent a combined extrahepatic bile duct resection (EHBDR) and liver resection (LR) for hilar cholangiocarcinoma (HC). The aim of this study was to analyze patient survival, morbidity, and mortality as well as to seek predictive factors. The 1-, 3-, and 5-year actuarial patient survival was 72%, 37%, and 22%, respectively. Median survival was 19 months. Hospital mortality, all due to septic complications, was 12%. Morbidity was observed in 32 patients (76%). Infections were the most dominant complication. Patients (n=11) with American Joint Committee on Cancer (AJCC) stage I or stage II tumors exhibited a superior survival compared with patients (n=31) with stage III or IV tumors (p=0.023). Patients with tumor-free lymph nodes (n=26) indicated a greater survival compared with patients with tumor-positive lymph nodes (n=16) (p=0.004). Patients undergoing vascular reconstructions indicated a trend toward higher mortality and lower survival (p=0.068). Over 20% of the patients with hilar cholangiocarcinoma can survive more than 5 years after a combined EHBDR and LR at the cost of 12% perioperative mortality and a 76% morbidity. Results might improve with the prevention of infectious complications and improved selection of patients to avoid vascular reconstruction and to predict a negative nodal state.

Orthotopic liver transplantation for portosystemic encephalopathy in an adult with congenital absence of the portal vein.

Congenital absence of the portal vein (CAPV) is a very rare venous malformation in which mesenteric venous blood drains directly into the systemic circulation. There is no portal perfusion of the liver and no portal hypertension. This abnormality is usually coincidentally discovered in children, the majority of whom have no signs of encephalopathy and only slightly abnormal liver function tests. Additional anomalies common in CAPV are cardiovascular abnormalities and hepatic tumors. To date, only 5 adult patients (>18 years) with CAPV have been described, none of whom underwent liver transplantation. We describe a 45-year-old man with CAPV and end-stage renal insufficiency due to focal segmental glomerulopathy, who developed therapy-resistant encephalopathy with intermittently high ammonia levels. The patient underwent a combined liver and kidney transplantation and is doing well at 2.5 years of follow-up. Histopathological examination of the native liver showed no portal vein branches in the portal tracts. In conclusion, our experience suggests that, although children with CAPV usually have no symptoms of encephalopathy, this may still develop at a later stage in adult life. When encephalopathy becomes refractory to medical therapy, orthotopic liver transplantation (OLT) can be successfully performed with restoration of normal cerebral function.

Retransplantation of the liver in adults: outcome and predictive factors for survival.

Hepatic retransplantation is considered to carry a higher risk than primary transplantation. Survival might improve with more experience and better immunosuppression. We studied all 55 patients who were adults at the time of their first retransplantation and who underwent retransplantation between 1979 and May 2001. Patient survival at 1, 5 and 10 years was 73%, 63%, and 63%, respectively. Multivariate analysis of pre-transplant variables revealed prothrombin time, creatinine level, and indication for retransplantation, as independent predictive factors. Survival was highest in patients who had undergone retransplantation for hepatic artery thrombosis. Multivariate analysis, including pre-, per-, and post-operative variables, showed that era of transplantation, prothrombin time, blood loss, and intensive care unit (ICU) stay, were independent predictive factors. Survival at 1 and 5 years improved from 56% and 48%, respectively, before 1996 to 89% and 81%, respectively, after 1996. In conclusion, survival after hepatic retransplantation improved significantly through the years. Independent pre-transplant predictive factors were prothrombin time, creatinine level, and indication for retransplantation.

LPS-induced downregulation of MRP2 and BSEP in human liver is due to a posttranscriptional process.

Endotoxin-induced cholestasis in rodents is caused by hepatic downregulation of transporters, including the basolateral Na+-dependent taurocholate transporter (ntcp) and the canalicular bile salt export pump (bsep) and multidrug resistance-associated protein 2 (mrp2). Details about the regulation of the human transporter proteins during this process are lacking. We used precision-cut human and rat liver slices to study the regulation of transporter expression during LPS-induced cholestasis. We investigated the effect of LPS on nitrate/nitrite and cytokine production in relation to the expression of inducible nitric oxide synthase, NTCP, BSEP, and MRP2 both at the level of mRNA with RT-PCR and protein using immunofluorescence microscopy. In liver slices from both species, LPS-induced expression of inducible nitric oxide synthase was detected within 1-3 h and remained increased over 24 h. In rat liver slices, this was accompanied by a significant decrease of rat ntcp and mrp2 mRNA levels, whereas bsep levels were not affected. These results are in line with previous in vivo studies and validate our liver slice technique. In LPS-treated human liver slices, NTCP mRNA was downregulated and showed an inverse correlation with the amounts of TNF-alpha and Il-1beta produced. In contrast, MRP2 and BSEP mRNA levels were not affected under these conditions. However, after 24-h LPS challenge, both proteins were virtually absent in human liver slices, whereas marker proteins remained detectable. In conclusion, we show that posttranscriptional mechanisms play a more prominent role in LPS-induced regulation of human MRP2 and BSEP compared with the rat transporter proteins.