[Neuroendocrine colorectal tumors. Surgical and endoscopic treatment]. / Neuroendokrine kolorektale Tumoren. Chirurgische und endoskopische Therapieverfahren.

The incidence of colorectal neuroendocrine tumors (NETs) is rising in developed countries primarily as a result of increased incidental detection by endoscopy and probably also due to a more adequate diagnosis according to the WHO classification. Less than 1% of colorectal NETs produce serotonin so that such tumors are practically never associated with a hormonal carcinoid syndrome. An exact clinico-pathological staging is of paramount importance for the therapeutic strategy and comprises the classification of the tumor type (well or poorly differentiated) and the assessment of established prognostic risk factors (depth of infiltration, vascular invasion, lymph node and distant metastases). Poorly differentiated colorectal NETs often present in an advanced, metastatic state, where surgical therapy is basically palliative. Well-differentiated tumors larger than 2 cm have a high risk of metastatic spread and should be treated as adenocarcinomas by radical oncological surgical resection. This applies to the majority of colon NETs. Tumors smaller than 1 cm, mainly locacted in the rectum, only rarely metastasize and are usually accessible for endoscopic treatment or transanal local surgery. Tumors between 1 and 2 cm in size have an uncertain prognosis and additional risk factors and co-morbidities of the patient have to be considered for a suitable, multidisciplinary therapeutic decision.

[Results of multivisceral resection of primary colorectal cancer]. / Ergebnisse der multiviszeralen Resektion des primären kolorektalen Karzinoms.

BACKGROUND: In about 10 % of all patients with colorectal cancer, the primary invention already discloses adhesions or infiltration of adjacent organs. En bloc resection of the tumor-bearing bowel segment with adjacent organs is done to give patients a chance for curation, since intraoperative differentiation is not possible. The aim of this study is characterization of the patient population as well as evaluation of the morbidity and mortality associated with this type of extensive intervention. METHOD: Between 1/95 and 6/04, we analyzed all patients with progressive primary colorectal cancer, who underwent multivisceral surgery with en bloc resection of at least one other organ. The target parameters were tumor characteristics as well as postoperative morbidity and mortality. RESULTS: A total of 1 001 patients with colorectal cancer underwent surgery. 101 patients (10 %) required multivisceral resection. In 17 % the indication was exigent. About 70 % of the interventions involved the colon. Tumor perforation was seen in 17 % of patients with colon cancer and 16 % with rectal cancer. Resection of the inner genitals was most frequent in both colon and rectal cancer (26 and 84 %) followed by small bowel resection (21 %) and partial bladder resection (19 %). Other organs play a secondary role in rectal cancer while partial bladder resection (20 %) and abdominal wall resection (14 %) is observed more frequently in colon cancer. Resection of parenchymatous organs (kidney, suprarenal gland, spleen, pancreas, liver) and others like the stomach is quite rare in colon cancer. Actual tumor infiltration (T4 situation) was observed in 51 % of patients with colon cancer and in 64 % of those with rectal cancer. Local R0 resection (97 vs. 96 %) was successfully performed in nearly all colon and rectal cancer patients. The surgical major complication rate was 9 % in colon cancer and 19 % in rectal cancer. The mortality rate was 4 %. CONCLUSION: Multivisceral en-bloc resection enables local R0 resection in the majority of cases with primary colorectal cancer. Despite sometimes extensive surgery, this type of procedure is associated with an acceptable morbidity and mortality. Since long-term survival is comparable to that in the T category (T3 or T4), multivisceral en-bloc resection is not only justified but also absolutely required in interventions with curative intention.

Selective inhibition of cyclooxygenase-2 (COX-2) reduces prostaglandin E2 production and attenuates systemic disease sequelae in experimental pancreatitis.

BACKGROUND/AIMS: Prostaglandins and prostaglandin-derived mediators play an important role in mediating the systemic inflammatory response in acute pancreatitis. COX (cyclooxygenase) is the key enzyme of prostaglandin synthesis. Whereas COX-1 produces prostaglandin mediators for physiological reactions, COX-2 is overexpressed in acute pancreatitis. The aim of this study was to investigate whether a selective COX-2 inhibitor alters prostaglandin production and attenuates systemic disease sequelae in severe acute pancreatitis in rats. METHODOLOGY: Severe acute pancreatitis was induced in 36 rats by standardized intraductal infusion of bile salt and intravenous cerulein infusion. Six hours after acute pancreatitis induction, rats were randomized to receive either no COX inhibition (saline), nonselective COX inhibition by indomethacin (3 mg/kg, i.v.) or selective COX-2 inhibition by NS-398 (10 mg/kg, i.v.). Serum concentrations of prostaglandin E2 were measured before and after acute pancreatitis induction and 24 hrs after starting therapy. Routine cardiorespiratory and renal parameters were monitored to assess organ function. RESULTS: Animals treated with the selective COX-2 inhibitor had significantly lower prostaglandin E2 values (211 +/- 17 vs. 366 +/- 37 and 435 +/- 13 pg/mL), produced more urine (18 +/- 4 vs. 13 +/- 3 and 12 +/- 3 mL/6-24 h) and had significantly fewer episodes of respiratory distress (defined as a pO2 < 80 mmHg or pCO2 > 50 mmHg for > 15 min; 12 vs. 57 and 71%) during the observation period than animals without or with nonselective COX inhibition. CONCLUSIONS: Selective inhibition of COX-2 reduces prostaglandin E2 serum levels in this model of acute pancreatitis. This together with improved renal and respiratory function suggests an attenuation of the systemic response to pancreatic injury. COX-2 inhibition may be another step toward optimizing therapy in severe acute pancreatitis.

Angiogenesis inhibitor TNP-470 reduces human pancreatic cancer growth.

In this study we investigated the effects of the angiogenesis inhibitor TNP-470 on human pancreatic cancer cells in vitro and in vivo. The action of TNP-470 on vascular endothelial growth factor (VEGF) was also assessed. In vitro human pancreatic cancer cells (MIAPaCa-2, AsPC-1, and Capan-1), and human umbilical vein endothelial cells (HUVEC) were exposed to increasing concentrations (1 pg/ml to 100 microg/ml) of TNP-470. Cell proliferation was assessed after 3 days by cell count and MTT assay. In vivo, 5 x 10(6) pancreatic cancer cells were injected subcutaneously into nude mice. Four weeks later, 1 mm3 fragments of the resulting tumors were implanted into the pancreas of other mice. Animals received either TNP-470 (30 mg/kg every other day) or vehicle subcutaneously for 14 weeks. The volume of the primary tumor and metastatic spread were determined at autopsy. Concentrations of VEGF were determined in serum (VEGF(S)) and ascites (VEGF(A)) by enzyme-linked immunosorbent assay. Microvessel density was analyzed by immunohistochemistry in CD31-stained tumor sections. In vitro, proliferation and viability of the human pancreatic cancer cell lines were significantly inhibited at high concentrations of TNP-470 (> 1 microg/ml). In contrast, TNP-470 effectively decreased the growth of HUVEC at 100 pg/ml. In vivo, tumor volume and dissemination scores were significantly lower in all three pancreatic cancer cell lines. VEGF(S) and VEGF(A) were not different between treated groups. Treatment with TNP-470 significantly reduced neoangiogenesis in tumors of all three human pancreatic cancer cell lines: MIAPaCa-2 = 74.8 +/- 7.8/0.74 mm2 vs. 24.8 +/- 3.7/0.74 mm2; AsPC-1 = 65.3 +/- 5.0/0.74 mm2 vs. 26.0 +/- 3.4/0.74 mm2; and Capan-1 = 82.2 +/- 5.8/0.74 mm2 vs. 26.9 +/- 2.5/0.74 mm2 (P < 0.001). However, survival was not statistically different between groups. TNP-470 reduced tumor growth and metastatic spread of pancreatic cancer in vivo. This was probably due to the antiproliferative effect of the agent on endothelial cells rather than to the direct inhibition of pancreatic cancer cell growth. TNP-470 activity was not associated with alteration of VEGF secretion.

Endothelin mediates local and systemic disease sequelae in severe experimental pancreatitis.

Endothelin-1 has been shown to reduce pancreatic blood flow and cause focal acinar cell necrosis similar to those seen in acute pancreatitis (AP), whereas therapy with endothelin receptor antagonists enhanced pancreatic capillary blood flow (PCBF) and decreased mortality rates. The current study evaluated the role of endothelin in the development of severe AP. Trypsinogen activation peptides, acinar cell necrosis, and PCBF were used as local indicators of disease severity, fluid sequestration, cardiorespiratory and renal parameters, and colonic capillary blood flow as systemic disease indicators. The following groups of animals were examined: 1) rats with mild edematous AP and 2) severe necrotizing AP treated with and without endothelin, 3) transgenic rats overexpressing endothelin with severe AP, and 4) rats with severe AP prophylactically treated with endothelin receptor antagonists. The following observations were made: endothelin superimposed on mild AP caused hemoconcentration, a decrease in PCBF, and necrosis and ascites not seen in this model without endothelin exposure. Endothelin superimposed on severe AP had no significant effects. After induction of severe AP, less PCBF and more acinar cell necrosis were observed in transgenic rats than in their normal littermates. Prophylactic endothelin receptor antagonists improved local (acinar necrosis, PCBF) and systemic parameters (ascites, urine production, colonic capillary blood flow) of disease severity in animals with severe AP. These observations underscore the role of endothelin as a mediator of disease severity in AP and suggest that endothelin receptor blockade may become a promising therapeutic tool in this disease.

An improved clinical model of orthotopic pancreatic cancer in immunocompetent Lewis rats.

The study of pancreatic cancer (PaCa) requires orthotopic, clinically relevant animal models. The aims of this study were to establish an orthotopic model of ductal pancreatic adenocarcinoma in immunocompetent Lewis rats and to develop a scoring system to quantify local tumor infiltration and distant metastasis. Cells (10(7)) of the rat ductal PaCa cell line DSL-6A/C1 were injected s.c. into donor rats. After 8 weeks, either three (IPL-3) or five (IPL-5) fragments (1 mm3) of the resulting s.c. tumors were microsurgically implanted into the pancreas of recipient rats. In another series of animals, 10(7) DSL-6A/C1 cells were directly injected (INJ) into the pancreas. All animals were monitored daily until death or for 16 weeks. At autopsy, volume of primary tumors and ascites, local and systemic tumor spread, and histologic phenotype were assessed. IPL-5 resulted in significantly larger tumors (12,224 +/- 1,933 mm3), more local infiltration and systemic spread (score: 18.3 +/- 2.0 points), severe clinical tumor disease, and lethality (50%) in comparison to the other induction techniques (IPL-3: 283 +/- 115 mm3/3.5 +/- 0.8 points/0; INJ: 752 +/- 207 mm3/4.3 +/- 0.8 points/8%). Histologic examination revealed moderately to well-differentiated ductal tumors, surrounded by dense stroma. Intraperitoneal tumor dissemination in the INJ group occurred simultaneous with primary tumor growth, indicating PaCa cell spread during injection. Orthotopic implantation of five DSL-6A/C1 tumor fragments into the rat pancreas provides a valid clinical model of ductal pancreatic adenocarcinoma in immunocompetent rodents for preclinical treatment studies. The dissemination score we used permitted quantification of local and systemic tumor spread.

Endothelin receptor blockade in severe acute pancreatitis leads to systemic enhancement of microcirculation, stabilization of capillary permeability, and improved survival rates.

BACKGROUND: We previously demonstrated that therapy with a new endothelin A receptor antagonist (ET-RA) significantly reduced mortality rates in severe acute pancreatitis (AP) in the rat without attenuating local signs of disease severity (intrapancreatic protease activation, acinar cell necrosis). This raised the question as to why ET-RA was so effective. The purpose of this study was to assess the effect of ET-RA on microcirculation (particularly capillary permeability) within and outside of the pancreas on intravascular fluid loss and extravascular fluid sequestration and on distant organ function. METHODS: Severe AP was induced in rats by standardized intraductal bile acid infusion and cerulein hyper-stimulation. Starting 6 hours (n = 24 rats) and 12 hours (n = 30 rats) after the onset of AP, animals randomly received either the ET-RA (LU-135252) or saline solution with fluid resuscitation (6 mL/kg/h Ringer's lactate). At 24 hours, animals were relaparotomized for intravital microscopic determination of capillary blood flow, leukocyte rolling, and capillary permeability in the pancreas and colon. Further monitoring included cardiorespiratory and renal parameters, hematocrit levels and quantification of ascites and pleural effusions, and acinar cell necrosis at autopsy. Groups of sham-operated healthy animals (n = 6 animals each) that had been treated according to the same protocol served as control animals. RESULTS: ET-RA treatment that was started 6 hours after AP-induction significantly decreased hematocrit levels (38% +/- 1% vs 45% +/- 2% with saline solution treatment), reduced ascites and pleural effusions (6.7 +/- 1.3 mL vs 11.9 +/- 1.3 mL), and improved urine production (4.8 +/- 0.5 mL vs 2.9 +/- 0.6 mL) and respiratory parameters. Moreover, all microcirculatory parameters were improved; in particular, capillary permeability was stabilized (158% +/- 9% vs 248% +/- 8% in the colon). These beneficial effects were also seen when therapy was delayed until 12 hours after AP induction. Pancreatic necrosis was not significantly reduced. The overall mortality rate was 12% in ET-RA-treated animals and 42% in saline solution-treated control animals (P <.05). In healthy animals ET-RA did not significantly alter the target parameters, except for a reduction of capillary permeability in the pancreas. CONCLUSIONS: Improved microcirculation and stabilized capillary permeability in ET-RA-treated animals together with reduced intravascular fluid loss and extravascular fluid sequestration and improved renal and pulmonary function (1) may explain improved survival in this model, (2) support the hypothesis that systemic disease sequelae significantly contribute to outcome in AP, and (3) suggest that ET-RA may be a promising therapeutic tool in AP because it counteracts microcirculatory disorders that contribute to pancreatitis-associated organ dysfunction even when therapy is delayed to a point at which pancreatic injury may no longer be influenced.

Experimental models of acute pancreatitis: are they suitable for evaluating therapy?

Since randomized controlled studies of severe acute human pancreatitis can be performed only with restrictions, at least some aspects of innovative therapy concepts should first be clarified in animal experiments. In vitro trials are inadequate for this purpose since they cannot simulate the complex course of severe acute pancreatitis. Animal test results can be transferred to clinical practice if the results are based on trials with established models, standardized methods, and a study design imitating the clinical situation. This contribution discusses the demands on such an animal model of acute pancreatitis and a corresponding study protocol and presents models and protocols which meet these requirements. Concrete examples are presented to show that animal experiments are of great value under these conditions, especially in acute necrotizing pancreatitis. Further standardization of models, protocols, and monitoring should further improve future animal therapy studies at least to the extent that it is possible to select particularly promising substances, which should then be tested in randomized controlled trials.

Animal models of exocrine pancreatic cancer.

Clinically and biologically relevant animal models are mandatory to further evaluate both the pathophysiology and novel strategies for diagnosis and treatment of exocrine pancreatic cancer. This review briefly summarizes the features of human pancreatic cancer in order to define requirements for animal models of the disease. The described model systems in rodents include pancreatic cancer induced by chemicals, pancreatic cancer in transgenic, and immunodeficient animals.

Effect of endothelin and endothelin receptor blockade on capillary permeability in experimental pancreatitis.

BACKGROUND: Capillary leakage with fluid loss into the third space contributes to many of the early systemic complications in severe acute pancreatitis. There has been increasing interest in endothelin as one of the factors affecting capillary permeability. AIM: To elucidate further the role of endothelin in the development of capillary leakage in acute pancreatitis by investigating the effect of exogenous endothelin administration and endothelin receptor blockade in sham operated animals and two models of acute pancreatitis. METHODS: Determination of capillary permeability in the pancreas and colonic mucosa by quantifying extravasation of fluorescein labelled dextran using a novel computer assisted video image analysis system. RESULTS: Pancreatic and colonic capillary permeability increased stepwise from mild to severe acute pancreatitis. Endothelin increased pancreatic and colonic capillary permeability in healthy animals and animals with mild acute pancreatitis but had no additional adverse effect in severe acute pancreatitis. Endothelin receptor blockade decreased pancreatic capillary permeability in sham operated rats but had no effect on the colon. In mild and severe acute pancreatitis, endothelin receptor blockade stabilised increased capillary permeability in both the pancreas and colon. CONCLUSIONS: Endothelin plays an important role in mediating capillary permeability in the pancreas. In severe pancreatitis, it increases capillary permeability even outside the pancreas, thereby contributing to capillary leakage. Endothelin receptor blockade significantly reduces capillary permeability in acute pancreatitis both in and outside the pancreas, suggesting a therapeutic approach to counteract capillary leakage in severe acute pancreatitis.

Therapy for microcirculatory disorders in severe acute pancreatitis: effectiveness of platelet-activating factor receptor blockade vs. endothelin receptor blockade.

Many of the complications of severe acute pancreatitis are the result of the amplifying effects of microcirculatory disruption. The factors causing microcirculatory disorders in acute pancreatitis involve vasoactive mediators such as platelet-activating factor (PAF) and endothelin-1 (ET) activated during the inflammatory response to pancreatic injury. To further evaluate the potential therapeutic role of specific receptor antagonists (RA) to these mediators, the present study compares the effect of PAF and ET receptor blockade on microcirculation and organ function in a well-established rodent model of severe acute pancreatitis. Six hours after acute pancreatitis induction, rats were randomized to therapy with ET-RA (50 mg/kg LU-135252), PAF-RA (82 microg/kg WEB-2170), or NaCl 0.9% (volume equivalent). After 18 hours of fluid resuscitation, animals were relaparotomized for intravital microscopic determination of capillary blood flow, leukocyte rolling, and capillary permeability in the pancreas and colon. Other measurements included cardiorespiratory parameters, hematocrit, pleural effusions, ascites, urine production, and survival. Compared to saline treatment both ET-RA and PAF-RA significantly improved capillary blood flow in the pancreas and colon, reduced leukocyte rolling, and stabilized capillary permeability. The beneficial effects of receptor antagonist treatment on microcirculation were associated with decreased fluid loss into the third space, improved renal and respiratory function, and survival. Although both receptor antagonists likewise improved capillary blood flow, ET-RA was significantly more effective in counteracting leukocyte rolling and capillary leakage, thereby further reducing fluid sequestration. The present study confirms the beneficial effects of PAf and ET receptor blockade on microcirculation inside and outside the pancreas, organ function, and survival when given at the early stage of severe pancreatitis. Because ET-RA was more effective in stabilizing capillary permeability and avoiding subsequent fluid loss into the third space, we propose that ET-RA should be tested in a clinical trial (either in comparison or in addition to PAF-RA).

Does glutamine reduce bacterial translocation? A study in two animal models with impaired gut barrier.

Failure of intestinal barrier function and subsequent translocation of bacteria from the gut are believed to play a decisive role in the development of systemic septic complications, for example, following major trauma or major abdominal surgery. This study evaluated: (a) the effect of glutamine on colonic microcirculation and electrophysiological parameters reflecting gut barrier function, (b) the translocation of live bacteria to extraintestinal organs, and (c) disease outcome in two animal models with impaired gut barrier function. Severe acute pancreatitis or colitis was induced in rats randomized for therapy with or without glutamine (0.5 g/kg daily). After 48 h one animal group was prepared for intravital microscopy of colonic capillary blood flow and electrophysiological measurement of gut permeability; another was killed after 96 h for histological and microbiological examination. In animals with pancreatitis, glutamine (Gln) supplementation significantly improved gut permeability, i.e., Gln increased colonic transmucosal resistance from 67+/-7 to 92+/-3 Omega/cm(2) and decreased mannitol flux through the epithelium by 53%. Capillary blood flow in the colonic mucosa was improved by 25%. The prevalence of pancreatic infections was reduced from 86% in animals on standard parenteral nutrition to 33% in animals given the Gln-enriched diet (P<0.05); mortality decreased by 32%. In colitis, Gln had no significant effect on these parameters except for improving colonic capillary blood flow in colon segments not adjacent to the major injury site. Glutamine supplementation improves colonic capillary blood flow, stabilizes gut permeability, and reduces secondary pancreatic infections and mortality in severe rodent pancreatitis, but it is not helpful in colitis. This confirms previous reports that glutamine stabilizes gut barrier function only in certain diseases. Our experimental data strongly suggest that acute pancreatitis (rather than colitis) is one of the diseases with gut barrier dysfunction in which glutamine substitution may be helpful to reduce bacterial translocation and should therefore be tested in a controlled clinical trial.

Systemic lymphocyte activation modulates the severity of diet-induced acute pancreatitis in mice.

To examine the role of lymphocyte activation in the development of local and systemic complications in acute pancreatitis, we compared disease severity of choline-deficient, 0.5% ethionine supplemented (CDE) diet-induced acute pancreatitis in T- and B-cell deficient SCID mice and immunocompetent C.B-17 mice. Twenty-five female SCID and 17 female C.B-17 mice were fasted for 24 h and fed a CDE diet for 72 h. Twenty SCID and 12 C.B-17 mice were bled and their organs removed for histologic evaluation. Five control animals of both kinds were fed a regular diet for 6 days. Lung, kidney, and pancreas were examined microscopically, and pancreatic damage scored. Apoptosis was detected by DNA nick-end labeling and confirmed by DNA laddering. Trypsinogen-activation peptide was measured by enzyme-linked immunosorbent assay (ELISA), and the catalytic activity of PLA2 was determined by a radiometric assay. Four-day mortality was 10% in SCID and 33% in C.B-17 mice, and 10-day mortality was 0 in SCID and 60% in C.B-17 mice. SCID mice had mild pulmonary damage, whereas pulmonary injury was severe in C.B-17 mice. Pancreatic damage was severe in both groups. Even though in situ staining of apoptotic cells was found in all pancreatitis animals, apoptosis was confirmed by DNA laddering only in C.B-17 mice. In SCID mice, apoptotic cell staining positively correlated with necrosis (r = 0.91; p < 0.001). Plasma TAP and PLA2 catalytic activity did not differ significantly between the groups. In conclusion, the absence of T and B lymphocytes prevents severe pulmonary injury resulting from acute pancreatitis but does not influence pancreatic or renal damage. Our results suggest that systemic lymphocyte activation does not affect the initiating events that trigger pancreatic injury but modulates the systemic response, in particular, pulmonary injury caused by acute pancreatitis.

Acute pancreatitis.

Efforts to unravel the intracellular processes that occur in acute pancreatitis continue. In cerulein pancreatitis, new evidence supports the idea that a very early event is premature trypsinogen activation triggered by lysosomal cathepsin B. Clinicians persist in trying to identify more sensitive and specific prognostic signs of the severity of attacks of pancreatitis; one study suggests that computer-based neural networks may be an alternative to biochemical markers and clinical scoring systems. The systemic severity of episodes of pancreatitis seems to be related to a multitude of proinflammatory cytokines and chemokines acting at sites distant from the pancreas. Selective blockade of some of these peptides (eg, endothelin-1 and platelet-activating factor) has decreased mortality and distant organ damage in animal models and may deserve clinical evaluation. Gene therapy may be more efficient than pharmacologic therapy in increasing anti-inflammatory cytokine (interleukin-10) levels. Clinical studies have further underlined the usefulness of prophylactic antibiotics in severe acute pancreatitis. Radiologic and endoscopic techniques may be alternatives to surgery for certain complications of pancreatitis (eg, infected necrosis and pseudocysts) in particular subsets of patients.

Endothelin-1 mediates the alcohol-induced reduction of pancreatic capillary blood flow.

Increased plasma endothelin-1 (ET-1) levels in rats after alcohol administration and increased endothelin receptor expression in the pancreas in chronic alcoholic pancreatitis have led to the hypothesis that ET-1 may play a critical role in the pathogenesis of ethanol-induced pancreatic injury through impairment of perfusion. To further test the hypothesis that ET-1 mediates an alcohol-induced reduction of pancreatic perfusion, the present study compares the effect of intravenous alcohol and ET-1 on pancreatic capillary blood flow (PCBF) and investigates whether endothelin receptor blockade prevents the alcohol-induced reduction in PCBF. Anesthetized rats were randomly assigned to receive one of the following: a 1-hour infusion of 2 g/kg alcohol or the volume equivalent of saline solution plus ET-1 (1.25 microgram/kg), a specific endothelin-A receptor antagonist (50 mg/kg), or saline solution (volume equivalent). The pancreas was exposed for intravital microscopy; PCBF was determined at the same location before the test solutions were given, after the infusion, and 1 hour thereafter. Alcohol and ET-1 significantly decreased PCBF from 2.0 nl/min/cap to 1.7 nl/min/cap. The reduction in PCBF was even more pronounced when alcohol and ET-1 were combined (1.5 nl/min/cap), whereas the ET receptor antagonist increased PCBF in saline-treated rats to 2.2 nl/min cap and maintained stable PCBF in alcohol-treated animals. The observation that PCBF is reduced by both alcohol and ET-1 and that the alcohol-induced reduction of PCBF can be aggravated by ET-1 and prevented by a specific endothelin-1 antagonist supports the hypothesis that ET-1 is the mediator of the alcohol-associated reduction of pancreatic perfusion.

Endothelin receptor blockade improves fluid sequestration, pancreatic capillary blood flow, and survival in severe experimental pancreatitis.

OBJECTIVE: To evaluate the effect of a new endothelin receptor antagonist (ET-RA) on the course of severe experimental pancreatitis. BACKGROUND: Endothelin-1 has been shown to reduce regional blood flow in various organs, including the pancreas, and to aggravate cerulein-induced mild pancreatitis. METHODS: Acute necrotizing pancreatitis (ANP) was induced in rats by standardized intraductal bile acid infusion and cerulein hyperstimulation. Serum trypsinogen activation peptides (TAP) were measured to verify comparable disease severity. Starting 6 hours after the onset of ANP, animals randomly received either saline or the new ET-RA LU-135252. Monitoring included cardiorespiratory parameters, urine output, hematocrit, and TAP levels. After 24 hours, animals were relaparotomized to determine pancreatic capillary blood flow and to assess the amount of free intraabdominal fluid and acinar cell necrosis. Survival was determined in a second set of experiments on 24 animals observed for 48 hours after pancreatitis induction and treatment with either normal saline or ET-RA. RESULTS: Comparable TAP increases confirmed equally severe ANP in both groups before treatment. Treatment with ET-RA significantly reduced the mortality rate, from 50% in untreated animals to 8%. Improved survival was associated with significantly decreased hematocrit, improved urinary output, decreased ascites, and increased pancreatic capillary blood flow. There were no significant differences in plasma TAP and acinar cell injury in the surviving animals of the two treatment groups. CONCLUSION: Therapy with the new ET-RA reduces the early mortality rate in experimental ANP, probably by reducing fluid sequestration and improving microcirculation.

Prophylactic thyroidectomy in MEN IIA: does the calcitonin level correlate with tumor spread?

BACKGROUND: The fate of patients with multiple endocrine neoplasia of type II A (MEN II A) is determined by medullary thyroid carcinoma, which occurs in all cases. This has led to the therapeutic concept of prophylactic thyroidectomy in affected family members with the goal of removing the thyroid before the manifestation of carcinoma. We investigated a prophylactically thyroidectomized MEN II A population to determine whether the highly specific and sensitive tumor marker calcitonin correlates with tumor spread. PATIENTS AND METHODS: Fifteen patients with MEN II A (aged 4-24 years) who had undergone prophylactic thyroidectomy since 1990 were included in the study. Baseline and pentagastrin-stimulated calcitonin levels were preoperatively determined in all cases. The indication for surgery was established on the basis of pathologic calcitonin levels in the first seven patients and on the basis of detected RET proto-oncogene mutation in the other eight patients. Bilateral central lymphadenectomy was performed in all patients in addition to thyroidectomy. RESULTS: Histology demonstrated C-cell hyperplasia in five patients (aged 4-13 years), unilateral medullary microcarcinoma in six (aged 9-17 years) and a bilateral medullary microcarcinoma in three cases (aged 17-24 years). One 9-year-old boy with bilateral microcarcinoma already had a lymph node metastasis. The mean baseline calcitonin level correlated with the histologic findings (r=0.71, P=0.003) but there was no correlation between pentagastrin-stimulated calcitonin levels and histology (r=0.21, P=0.47). CONCLUSION: In MEN II A patients undergoing prophylactic thyroidectomy, baseline but not stimulated calcitonin levels already correlate with the histologic tumor stage at the stage of clinically occult C-cell hyperplasia or medullary microcarcinoma. However, biochemical screening cannot reliably discriminate the transition from C-cell hyperplasia to invasive microcarcinoma. Individuals with MEN IIA should therefore undergo early prophylactic thyroidectomy once the diagnosis is confirmed by molecular genetic testing.

Intestinal microcirculation and gut permeability in acute pancreatitis: early changes and therapeutic implications.

Translocation of bacteria from the intestine causes local and systemic infection in severe acute pancreatitis. Increased intestinal permeability is considered a promoter of bacterial translocation. The mechanism leading to increased gut permeability may involve impaired intestinal capillary blood flow. The aim of this study was to evaluate and correlate early changes in capillary blood flow and permeability of the colon in acute rodent pancreatitis of graded severity. Edematous pancreatitis was induced by intravenous cerulein; necrotizing pancreatitis by intravenous cerulein and intraductal glycodeoxycholic acid. Six hours after induction of pancreatitis, the permeability of the ascending colon was assessed by the Ussing chamber technique; capillary perfusion of the pancreas and colon (mucosal and subserosal) was determined by intravital microscopy. In mild pancreatitis, pancreatic capillary perfusion remained unchanged (2.13 c 0.06 vs. 1.98 +/-0.04 nl x min(-1) x cap(-1) [control]; P = NS), whereas mucosal (1.59 +/-0.03 vs. 2.28 +/-0.03 nl x min(-1) x cap((-1))[control]; P <0.01) and subserosal (2.47 +/-0.04 vs. 3.74 +/-0.05 nl x min(-1) x cap((-1))[control]; P <0.01) colonic capillary blood flow was significantly reduced. Severe pancreatitis was associated with a marked reduction in both pancreatic (1.06 +/-0.03 vs. 1.98 +/-0.04 nl x min(-1) x cap(-1) [control]; P <0. 01) and colonic (mucosal: 0.59 +/-0.01 vs. 2.28 +/-0.03 nl x min(-1) x cap((-1))[control], P <0.01; subserosal: 1.96 +/-0.05 vs. 3.74 +/-0.05 nl x min(-1) x cap(-1) [control], P <0.01) capillary perfusion. Colon permeability tended to increase with the severity of the disease (control: 147 +/-19 nmol x thr(-1) x cm(-2); mild pancreatitis: 158 +/-23 nmol x hr(-1) x cm(-2); severe pancreatitis: 181 +/-33 nmol x hr(-1) x cm(-2); P = NS). Impairment of colonic capillary perfusion correlates with the severity of pancreatitis. A decrease in capillary blood flow in the colon, even in mild pancreatitis not associated with significant protease activation and acinar cell necrosis or impairment of pancreatic capillary perfusion, suggests that colonic microcirculation is especially susceptible to inflammatory injury. There was no significant change in intestinal permeability in the early stage of pancreatitis, suggesting a window of opportunity for therapeutic interventions to prevent the later-observed increase in gut permeability, which could result in improved intestinal microcirculation.

[Endothelin receptor block in acute pancreatitis--improvement of microcirculation and decrease of capillary permeability also distant from the pancreas]. / Endothelin-Rezeptorenblockade bei akuter Pankreatitis--Verbesserung der Mikrozirkulation und Verminderung der Kapillarpermeabilität auch ausserhalb des Pankreas.

We have previously demonstrated that therapy with a new specific endothelin-1 receptor antagonist (ET-RA) significantly reduced mortality in acute necrotizing pancreatitis (ANP) in the rat. Improved survival was not associated with decreased intrapancreatic trypsinogen activation or parenchymal necrosis but with reduced fluid sequestation into the third space suggesting that ET-RA counteracts systemic rather than local sequelae of severe pancreatitis. The present study further tests this hypothesis by evaluating the effect of the specific ET-1 antagonist LU-135252 on capillary blood flow, capillary density, and capillary permeability not only in the pancreas but also in the colon, and monitoring fluid losses and renal and respiratory function. The experiments demonstrate that therapy with the specific ET-RA started 6 hours after disease onset stabilizes increased capillary permeability in ANP not only in the pancreas but also in the colon. This is associated with reduced ascites and improved renal and respiratory function. Furthermore, ET-RA enhances decreased capillary blood flow and capillary density in the pancreas and colon. The present results are consistent with our previous observation that ET-RA improves outcome in ANP by counteracting systemic microcirculatory disorders (particularly capillary leakage) which are believed to contribute to organ failure in early pancreatitis in this model as well as in severe human pancreatitis.

Influence of changes in pancreatic tissue morphology and capillary blood flow on antibiotic tissue concentrations in the pancreas during the progression of acute pancreatitis.

BACKGROUND: The ability of an antibiotic to reach bactericidal concentrations in tissue depends on numerous factors including tissue composition and regional perfusion. Although necrotising pancreatitis is characterised by progression of pancreatic necrosis over at least 96 hours and microcirculatory alterations, the impact of these changes on the concentration of antibiotics in the pancreas has not yet been investigated. AIM: To determine and compare pancreatic tissue concentrations of imipenem and cefotaxime at different stages of acute necrotising pancreatitis in an animal model that has been shown to mimic closely the pathomorphological and bacteriological features of severe human pancreatitis. METHOD: Acute necrotising pancreatitis was induced in rats by a standardised intraductal infusion of glycodeoxycholic acid and intravenous cerulein. Six hours (n = 16) and 48 hours (n = 16) after induction of pancreatitis, the animals were randomised for intravenous therapy with either imipenem or cefotaxime. Fifteen minutes after injection of the antibiotic, the animals were killed. Blood and the head of the pancreas were collected for determining imipenem or cefotaxime in serum and tissue; the splenic portion of the pancreas was prepared for histological examination. In an additional set of identically treated animals, pancreatic capillary blood flow (PCBF) was assessed by intravital microscopy before induction of acute necrotising pancreatitis and at the time of antibiotic therapy. RESULTS: Imipenem accumulates in the pancreas in the initial phase of acute necrotising pancreatitis characterised by pronounced oedema and decreased PCBF, and tends to decrease with resolution of the oedema and the progression of acinar cell necrosis in the later course of the disease. Concentrations of cefotaxime are low in oedematous pancreatic tissue early after induction of acute necrotising pancreatitis and increase with the resolution of oedema and normalisation of PCBF. CONCLUSIONS: Concentrations of antibiotics in the pancreas vary in acute necrotising pancreatitis, depending on changes in pancreatic tissue morphology and capillary blood flow. This suggests that antibiotic tissue concentrations may not be consistent from one agent to another and that efficacy of antibiotics in acute pancreatitis cannot be estimated solely on the basis of their pharmacological and microbiological properties.