Method for adequate macroscopic gallbladder examination after cholecystectomy

BACKGROUND AND AIMS

There is no clear guideline nor protocol for macroscopic examination of the gallbladder, leaving surgeons extemporaneous in regard of gallbladder examination in selective histopathologic policy. The purpose of this article is to describe a surgical approach for adequate macroscopic inspection of the gallbladder.

MATERIALS AND METHODS

The described practical method was developed in collaboration between surgeons and pathologists. This method was introduced in 2011 and implemented in 2012. We retrospectively reviewed the number of cholecystectomies and number of histopathologic examinations between 2006 and 2017, using our own patient database. We used the Netherlands Cancer Registry (NCR) to examine the incidence of gallbladder cancer patients before and after implementation of the selective policy in our hospital. In addition to the method, we depict several frequent macroscopic abnormalities in order to provide some examples for surgical colleagues.

RESULTS

Since implementation of the selective policy, 2271 surgical macroscopic gallbladder examinations were performed. As a result, we observed a significant decrease from 83% in 2012 to 38% in 2017, in histopathologic examination of the gallbladder following cholecystectomy. We observed a stable trend of gallbladder carcinoma in the same period (0.17%, n = 4 during 2006-2011 and 0.26%, n = 6 during 2012-2017).

CONCLUSION

A simple, valid and easy method is described for future macroscopic analysis by the surgeon following a cholecystectomy.

Management of the pancreatic transection plane after left (distal) pancreatectomy: Expert consensus guidelines by the International Study Group of Pancreatic Surgery (ISGPS)

BACKGROUND

The aim was to evaluate the various operative techniques and outcomes used to manage the pancreatic transection plane (or stump) during a left (distal) pancreatectomy and to develop expert consensus guidelines.

METHODS

Evidence-based, clinically relevant questions were discussed and then were circulated among members of the International Study Group of Pancreatic Surgery. After agreement on the questions and statements, voting in a 9-point Likert scale was used to gauge the level of objective support for each.

RESULTS

Studies using the International Study Group of Pancreatic Surgery definition of postoperative pancreatic fistula including 16 randomized trials were reviewed to generate a series of statements set into 14 domains. There was strong consensus in the following statements: there was no difference in the postoperative pancreatic fistula rate after left pancreatectomy between the handsewn and stapler techniques; a stapling technique could not be used in all cases of left pancreatectomy; the use of an energy-based tissue sealant or a chemical sealant device or combinations of these did not impact the postoperative pancreatic fistula rate; there was no difference in the postoperative pancreatic fistula rate between the open, laparoscopic, or robotic approaches; and there are 1 or more clinically important, patient-related risk factors associated with the postoperative pancreatic fistula rate. There was weak or conditional agreement on the use of prophylactic somatostatin analogs, stents, stump closure, stump anastomosis, and the role of abdominal drains.

CONCLUSION

Areas of strong consensus suggests a change in clinical practice and priority setting. Eight domains with lower agreement will require novel approaches and large multicenter studies to determine future key areas of practice.

Effect of Early Surgery vs Endoscopy-First Approach on Pain in Patients With Chronic Pancreatitis: The ESCAPE Randomized Clinical Trial

IMPORTANCE

For patients with painful chronic pancreatitis, surgical treatment is postponed until medical and endoscopic treatment have failed. Observational studies have suggested that earlier surgery could mitigate disease progression, providing better pain control and preserving pancreatic function.

OBJECTIVE

To determine whether early surgery is more effective than the endoscopy-first approach in terms of clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS

The ESCAPE trial was an unblinded, multicenter, randomized clinical superiority trial involving 30 Dutch hospitals participating in the Dutch Pancreatitis Study Group. From April 2011 until September 2016, a total of 88 patients with chronic pancreatitis, a dilated main pancreatic duct, and who only recently started using prescribed opioids for severe pain (strong opioids for ≤2 months or weak opioids for ≤6 months) were included. The 18-month follow-up period ended in March 2018.

INTERVENTIONS

There were 44 patients randomized to the early surgery group who underwent pancreatic drainage surgery within 6 weeks after randomization and 44 patients randomized to the endoscopy-first approach group who underwent medical treatment, endoscopy including lithotripsy if needed, and surgery if needed.

MAIN OUTCOMES AND MEASURES

The primary outcome was pain, measured on the Izbicki pain score and integrated over 18 months (range, 0-100 [increasing score indicates more pain severity]). Secondary outcomes were pain relief at the end of follow-up; number of interventions, complications, hospital admissions; pancreatic function; quality of life (measured on the 36-Item Short Form Health Survey [SF-36]); and mortality.

RESULTS

Among 88 patients who were randomized (mean age, 52 years; 21 (24%) women), 85 (97%) completed the trial. During 18 months of follow-up, patients in the early surgery group had a lower Izbicki pain score than patients in the group randomized to receive the endoscopy-first approach group (37 vs 49; between-group difference, -12 points [95% CI, -22 to -2]; P = .02). Complete or partial pain relief at end of follow-up was achieved in 23 of 40 patients (58%) in the early surgery vs 16 of 41 (39%)in the endoscopy-first approach group (P = .10). The total number of interventions was lower in the early surgery group (median, 1 vs 3; P < .001). Treatment complications (27% vs 25%), mortality (0% vs 0%), hospital admissions, pancreatic function, and quality of life were not significantly different between early surgery and the endoscopy-first approach.

CONCLUSIONS AND RELEVANCE

Among patients with chronic pancreatitis, early surgery compared with an endoscopy-first approach resulted in lower pain scores when integrated over 18 months. However, further research is needed to assess persistence of differences over time and to replicate the study findings.

TRIAL REGISTRATION

ISRCTN Identifier: ISRCTN45877994.

Paraganglion, a pitfall in diagnosis after regular cholecystectomy

•

Neuroendocrine neoplasms are a rarity after cholecystectomy and current literature is scarce.

•

Paraganglion of the gallbladder is an incidental benign finding.

•

A paraganglion can mimic the histopathologic appearance of neuroendocrine tumours.

Introduction

Neuroendocrine neoplasm of the gallbladder is an extremely uncommon diagnosis. We present a case of a benign gallbladder paraganglion that was initially incorrectly diagnosed as a neuroendocrine tumour (NET).

Presentation of case

A 27-year-old female with symptomatic gallstone disease underwent an uncomplicated laparoscopic cholecystectomy. Routine histopathologic examination suggested the presence of a small adventitial NET. However, histopathological revision was performed by our pathologist because of regional gallbladder carcinoma (GBC) treatment evaluation. The revision demonstrated the presence of a normal paraganglion, a preexistent structure that is only rarely encountered during routine histopathologic examination of the gallbladder.

Discussion

Neuroendocrine neoplasms of the gallbladder are extremely rare. Treatment varies from a simple cholecystectomy to extensive surgical resections. Chemotherapy is usually reserved for metastatic disease. In contrast, a gallbladder paraganglion is a benign entity not requiring additional treatment.

Conclusion

A neuroendocrine neoplasm of the gallbladder may closely resemble a benign paraganglion. If a NET is suspected, the clinician should be aware of the histopathologic mimicry of a paraganglion prior to initiating additional treatments.

Selective Histological Examination After Cholecystectomy: An Analysis of Current Daily Practice in The Netherlands

BACKGROUND

The 2016 Dutch national guidelines on handling of a removed gallbladder for cholelithiasis proposes a selective histopathologic policy (Sel-HP) rather than routine policy (Rout-HP). The aim of this study was to determine the current implementation of the present guideline and the daily practice of Sel-HP.

METHODS

Surgeons who were engaged in gallbladder surgery in the Netherlands and were involved in local hospitals' gallbladder protocols completed a questionnaire study regarding gallbladder policy, between December 2017 and May 2018. Data were analyzed using standard statistics.

RESULTS

A 100% response rate was obtained (n = 74). Approximately 64% of all gallbladders (n = 22,500) were examined microscopically. Sixty-nine (93.2%) hospitals confirmed they were aware of the new guidelines, and 56 (75.7%) knew the guideline was adjusted in favor of Sel-HP. Half of the hospitals (n = 35, 47.3%) had adopted a Sel-HP, and 39 (52.7%) a Rout-HP. Of the 39 hospitals who had a Rout-HP, 36 were open to a transition to a Sel-HP although some expressed the need for more evidence on safety or novel guidelines.

CONCLUSIONS

The current implementation of the 2016 Dutch guideline advising a selective microscopic analysis of removed gallbladders for gallstone disease is suboptimal. Evidence demonstrating safety and cost-effectiveness of an on demand histopathological examination will aid in the implementation process.

Circulating Levels of Osteopontin Predict Patients' Outcome after Resection of Colorectal Liver Metastases

For colorectal liver metastases (CRLM), surgical resection is the only potentially curative therapy, but even successfully resected patients often face disease recurrence, leading to 5-year survival rate below 50%. Despite available preoperative stratification strategies, it is not fully elucidated which patients actually benefit from CRLM resection. Here we evaluated osteopontin, a secreted glyco-phosphoprotein, as a biomarker in the context of CRLM resection. Tissue levels of osteopontin were analysed in CRLM using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. Pre- and postoperative osteopontin serum concentrations were analysed by enzyme-linked immunosorbent assay (ELISA) in 125 patients undergoing resection of CRLM as well as 65 healthy controls. Correlating with an upregulation of osteopontin tissue expression in CRLM, osteopontin serum levels were significantly elevated in patients with CRLM compared to healthy controls. Importantly, high pre- and post-operative osteopontin serum levels were associated with a poor prognosis after tumour resection. Patients with initial osteopontin serum levels above our ideal cut-off value of 264.4 ng/mL showed a significantly impaired median overall survival of 304 days compared to 1394 days for patients with low osteopontin levels. Together, our data suggest a role of osteopontin as a prognostic biomarker in patients with resectable CRLM that might help to identify patients who particularly benefit from liver resection.

Colicky pain and related complications after cholecystectomy for mild gallstone pancreatitis

BACKGROUND

Same-admission cholecystectomy is advised after gallstone pancreatitis to prevent recurrent pancreatitis, colicky pain and other complications, but data on the incidence of symptoms and complications after cholecystectomy are lacking.

METHODS

This was a prospective cohort study during the previously published randomized controlled PONCHO trial on timing of cholecystectomy after mild gallstone pancreatitis. Data on healthcare consumption and questionnaires focusing on colicky pain and biliary complications were obtained during 6 months after cholecystectomy. Main outcomes were (i) postoperative colicky pain as reported in questionnaires and (ii) medical treatment for postoperative symptoms and gallstone related complications.

RESULTS

Among 262 patients who underwent cholecystectomy after mild gallstone pancreatitis, 28 of 191 patients (14.7%) reported postoperative colicky pain. The majority of these were reported within 2 months after surgery and were single events. Overall, 25 patients (9.5%) required medical treatment for symptoms or gallstone related complications. Acute readmission was required in seven patients (2.7%). No predictors for the development of postoperative colicky pain were identified.

DISCUSSION

Some 15% of patients experienced colicky pain after cholecystectomy for mild gallstone pancreatitis, which were mostly single events and rarely required readmission. These data may be used to better inform patients undergoing cholecystectomy for mild gallstone pancreatitis.

Whole-volume vs. segmental CT texture analysis of the liver to assess metachronous colorectal liver metastases

PURPOSE

It is unclear whether changes in liver texture in patients with colorectal cancer are caused by diffuse (e.g., perfusional) changes throughout the liver or rather based on focal changes (e.g., presence of occult metastases). The aim of this study is to compare a whole-liver approach to a segmental (Couinaud) approach for measuring the CT texture at the time of primary staging in patients who later develop metachronous metastases and evaluate whether assessing CT texture on a segmental level is of added benefit.

METHODS

46 Patients were included: 27 patients without metastases (follow-up >2 years) and 19 patients who developed metachronous metastases within 24 months after diagnosis. Volumes of interest covering the whole liver were drawn on primary staging portal-phase CT. In addition, each liver segment was delineated separately. Mean gray-level intensity, entropy (E), and uniformity (U) were derived with different filters (σ0.5-2.5). Patients/segments without metastases and patients/segments that later developed metachronous metastases were compared using independent samples t tests.

RESULTS

Absolute differences in entropy and uniformity between the group without metastases and the group with metachronous metastases group were consistently smaller for the segmental approach compared to the whole-liver approach. No statistically significant differences were found in the texture measurements between both groups.

CONCLUSIONS

In this small patient cohort, we could not demonstrate a clear predictive value to identify patients at risk of developing metachronous metastases within 2 years. Segmental CT texture analysis of the liver probably has no additional benefit over whole-liver texture analysis.

Minimally invasive versus open distal pancreatectomy (LEOPARD): study protocol for a randomized controlled trial

BACKGROUND

Observational cohort studies have suggested that minimally invasive distal pancreatectomy (MIDP) is associated with better short-term outcomes compared with open distal pancreatectomy (ODP), such as less intraoperative blood loss, lower morbidity, shorter length of hospital stay, and reduced total costs. Confounding by indication has probably influenced these findings, given that case-matched studies failed to confirm the superiority of MIDP. This accentuates the need for multicenter randomized controlled trials, which are currently lacking. We hypothesize that time to functional recovery is shorter after MIDP compared with ODP even in an enhanced recovery setting.

METHODS

LEOPARD is a randomized controlled, parallel-group, patient-blinded, multicenter, superiority trial in all 17 centers of the Dutch Pancreatic Cancer Group. A total of 102 patients with symptomatic benign, premalignant or malignant disease will be randomly allocated to undergo MIDP or ODP in an enhanced recovery setting. The primary outcome is time (days) to functional recovery, defined as all of the following: independently mobile at the preoperative level, sufficient pain control with oral medication alone, ability to maintain sufficient (i.e. >50%) daily required caloric intake, no intravenous fluid administration and no signs of infection. Secondary outcomes are operative and postoperative outcomes, including clinically relevant complications, mortality, quality of life and costs.

DISCUSSION

The LEOPARD trial is designed to investigate whether MIDP reduces the time to functional recovery compared with ODP in an enhanced recovery setting.

TRIAL REGISTRATION

Dutch Trial Register, NTR5188 . Registered on 9 April 2015.

Dutch Chronic Pancreatitis Registry (CARE): design and rationale of a nationwide prospective evaluation and follow-up

BACKGROUND

Chronic pancreatitis is a complex disease with many unanswered questions regarding the natural history and therapy. Prospective longitudinal studies with long-term follow-up are warranted.

METHODS

The Dutch Chronic Pancreatitis Registry (CARE) is a nationwide registry aimed at prospective evaluation and follow-up of patients with chronic pancreatitis. All patients with (suspected) chronic or recurrent pancreatitis are eligible for CARE. Patients are followed-up by yearly questionnaires and review of medical records. Study outcomes are pain, disease complications, quality of life, and pancreatic function. The target sample size was set at 500 for the first year and 1000 patients within 3 years.

RESULTS

A total of 1218 patients were included from February 2010 until June 2013 by 76 participating surgeons and gastroenterologist from 33 hospitals. Participation rate was 90% of eligible patients. Eight academic centers included 761 (62%) patients, while 25 community hospitals included 457 (38%). Patient centered outcomes were assessed by yearly questionnaires, which had a response rate of 85 and 82% for year 1 and 2, respectively. The median age of patients was 58 years, 814 (67%) were male, and 38% had symptoms for less than 5 years.

DISCUSSION

The CARE registry has successfully recruited over 1200 patients with chronic and recurrent pancreatitis in about 3 years. The defined inclusion criteria ensure patients are included at an early disease stage. Participation and compliance rates are high. CARE offers a unique opportunity with sufficient power to investigate many clinical questions regarding natural course, complications, and efficacy and timing of treatment strategies.

Pancreas-preserving total duodenectomy versus standard pancreatoduodenectomy for patients with familial adenomatous polyposis and polyps in the duodenum

BACKGROUND

Pancreas-preserving total duodenectomy (PPTD) was introduced as a replacement for pancreatoduodenectomy (PD) for familial adenomatous polyposis (FAP). This study analysed the results of PPTD in the Netherlands and reviewed the relevant literature.

METHODS

All 26 patients who underwent PPTD for FAP in four centres in the Netherlands between January 2000 and January 2007 were compared with a group of 77 patients who had PD for ampulla of Vater adenocarcinoma at one centre during the same interval.

RESULTS

Morbidity rates were similar after PPTD for FAP (16 patients, 62 per cent) and PD for ampulla of Vater adenocarcinoma (44 patients, 57 per cent) (P = 0.694). One patient (4 per cent) died after PPTD and two (3 per cent) after PD. A review of the literature, including patients from the present study, found that 71 patients had PPTD, with postoperative morbidity in 36 (51 per cent) and one death (1 per cent). In publications containing a total of 94 patients who underwent PD for FAP, 43 (46 per cent) developed complications and three (3 per cent) died.

CONCLUSION

PPTD has similar short-term results to PD in terms of morbidity and mortality.

Intestinal function and metabolism in the early adaptive phase after massive small bowel resection in the rat

PURPOSE

The aim of this study was to investigate the early adaptive responses in metabolism and gut function after massive small bowel resection.

METHODS

Male Wistar rats underwent an 80% small bowel resection (Ent group, n = 9) or a transection and reanastomozing (Sham group, n = 7). After 24 hours, substrate fluxes across the gut were determined together with intestinal protein synthesis, polyamine concentrations in gut tissue, and gut function by testing intestinal permeability using the urinary recovery of lactulose and rhamnose. To test for the effect of starvation, healthy starved rats were studied.

RESULTS

In the Ent group, intestinal uptake of glucose, lactate, glutamine, phenylalanine, branched chain amino acids, and total amino acids were equal to or higher than that in Sham rats. Intestinal protein synthesis increased, accompanied by an increase in spermidine to spermine polyamine ratios in the ileum and in the jejunal muscular layer. The urinary lactulose to rhamnose ratio also increased, suggesting increased intestinal permeability.

CONCLUSIONS

24 hours after massive small bowel resection, adaptive responses in metabolism and gut function already can be observed, as indicated by increased intestinal uptake of substrates and increased protein synthesis. This, however, is accompanied by an increase in intestinal permeability, which may indicate impaired intestinal barrier function. J Pediatr Surg 36:1746-1751.

Nutrition in patients with acute pancreatitis

Acute pancreatitis is a disease with varying severity. Patients with the mild form do not require nutritional support because oral intake is resumed rapidly. Studies on nutritional support in acute pancreatitis have included patients with both mild and severe disease. In this heterogeneous group, total parenteral nutrition did not improve outcome compared with no nutrition at all. This is caused in part by an increase in septic complications during total parenteral nutrition. Likewise, no benefit from enteral nutrition was observed compared with no nutrition, probably because the group was heterogeneous or because nutritional goals were not achieved. Patients with severe acute pancreatitis become profoundly catabolic. This group undoubtedly requires nutritional support to treat undernutrition. The limited available data indicate that enteral nutrition, if well tolerated, is superior to parenteral nutrition for patients with severe acute pancreatitis. Based on current knowledge, a combination of early total parenteral nutrition and enteral nutrition is advisable as soon as enteral nutrition is tolerated. Monitoring of gut function is crucial in this situation.

Virtual hepatic resection using three-dimensional reconstruction of helical computed tomography angioportograms

OBJECTIVE

To establish the accuracy of virtual hepatic resection using three-dimensional (3D) models constructed from computed tomography angioportography (CTAP) images in determining the liver volume (LV) resected during resectional liver surgery.

SUMMARY BACKGROUND DATA

The ability to measure LV before surgery could be useful in determining the extent and nature of hepatic resection. Accurate assessment of LV and an estimate of liver function may also allow prediction of postoperative liver failure in patients undergoing resection, assist in volume-enhancing embolization procedures, help with the planning of staged hepatic resection for bilobar disease, and aid in selection of living-related liver donors.

METHODS

A retrospective study was conducted involving 27 patients scheduled for liver resection. Using mapping technology, 3D models were constructed from helical CTAP images. From these 3D models, tumor volume, total LV, and functional LV were calculated and were compared with body weight. The 3D liver models were subjected to a virtual hepatectomy along established anatomical planes, and the resected LV was calculated. The resected volume predicted by radiologists (unaware of the actual weight) was compared with the specimen weight measured after actual surgical resection.

RESULTS

A significant correlation was found between body weight and functional LV but not total LV. The computer prediction of resected LV after virtual hepatectomy of 3D models compared well with resected liver weight.

CONCLUSION

Virtual hepatectomy of 3D CTAP reconstructed images provides an accurate prediction of liver mass removed during subsequent hepatic resection. The authors intend to combine this technology with an assessment of liver function to attempt to predict patients at risk for liver failure after hepatic resection.

Renal amino acid metabolism during endotoxemia in the rat

BACKGROUND

The kidney has an important function in the exchange of nitrogenous metabolites. Glutamine is the most important substrate for renal ammoniagenesis and thus plays a crucial role in acid-base homeostasis. Furthermore, the kidney is the main endogenous source for de novo arginine production from citrulline, which in turn is derived from intestinal glutamine metabolism. Sepsis is a condition in which glutamine availability is reduced, whereas the need for arginine biosynthesis may be increased. Limited bioavailability of glutamine may affect arginine synthesis, which may have consequences for nitric oxide (NO) synthesis. Therefore, we studied renal glutamine and arginine metabolism in a rat model of endotoxemia and related this to NO metabolism.

MATERIALS AND METHODS

Rats were subject to double hit endotoxemia, and control rats received 0.9% NaCl. Renal blood flow was measured using para-aminohippuric acid. Concentrations of plasma amino acids and nitrate were measured in the aorta and renal vein to calculate net renal uptake or release of amino acids and address NO production.

RESULTS

The arterial concentrations of glutamine and ammonia were not changed in endotoxemic rats. Although renal glutamine uptake was reduced, total renal ammonia production was not changed during endotoxemia. The arterial concentration of citrulline and renal citrulline uptake was not altered in endotoxin-treated rats, but renal arginine production was increased. However, no effect was observed on nitric oxide production.

CONCLUSIONS

Although the kidney has very important functions in the excretion of waste products and in interorgan metabolism, this study suggests that the kidney has a limited role in glutamine, arginine, and NO metabolism during late endotoxemia in rats.

Splenic abscess after appendicitis

We report an appendicitis complicated by a splenic abscess in a patient with polycystic kidneys and multiple cystic lesions in the liver. Clinical decision making for operative intervention was made difficult by the extensive intra-abdominal abnormalities seen on computer tomography. Finally curation was achieved by splenectomy and appendectomy.

Enhanced renal vein ammonia efflux after a protein meal in the pig

BACKGROUND/AIMS

The intake of dietary protein has been associated with increased arterial ammonia levels. However, the origin of this rise in ammonia levels is unknown. This study was designed to examine whether this increase is caused by ammonia formed by the gut escaping hepatic clearance, or ammonia formed by the kidney and subsequently released into the circulation.

METHODS

Splanchnic and renal fluxes of ammonia and amino acids were studied in 10 pigs that were fed in a randomized cross-over design with a protein meal (n = 8), a meal with an equimolar amount of free amino acids (n = 8) or an iso-osmolar NaCl solution (n = 6).

RESULTS

After the protein meal, and less pronounced after the amino acid meal, arterial ammonia levels increased from approximately 25 to 75 micromol/l. Arterial pH changes and splanchnic ammonia release were negligible. The renal vein ammonia efflux increased after the protein meal (0.67+/-0.10 to 1.94+/-0.35 micromol/kg bw/min) and to a lesser degree after the amino acid meal (to 1.20+/-0.39 micromol/kg bw/ min). Renal uptake of alanine, and not glutamine, increased stoichiometrically, paralleling the enhanced renal vein ammonia efflux.

CONCLUSIONS

Arterial ammonia increases after a meal in pigs, coinciding with a negligible splanchnic ammonia release, but increased renal vein ammonia efflux. Thus, post-prandial plasma ammonia levels appear to be mainly related to renal ammoniagenesis. Alanine appears to be the main precursor for this renal ammoniagenesis in the pig.

Glutamine: the pivot of our nitrogen economy?

Glutamine serves as a shuttle of useful nontoxic nitrogen, supplying nitrogen from glutamine-producing (eg, muscle) to glutamine-consuming tissues. True production rates of glutamine are difficult to measure, but probably are less than 60 to 100 g/d for a 70-kg man. During catabolic stress increased amounts of glutamine are released from muscle, consisting of protein derived glutamine, newly synthesized glutamine, and glutamine losses from the intramuscular free pool. The large and rapid losses of free muscle glutamine are difficult to restore, presumably as a result of disturbances in the Na+ electrochemical gradient across the cell membrane. Whereas increased amounts of glutamine are released from muscle, glutamine consumption by the immune system (liver, spleen) also is enhanced. Thus, during catabolic stress changes occur in the flow of glutamine between organs. These changes are not necessarily reflected by alterations in the whole-body appearance rate of glutamine. In contrast with the gut, where glutamine is taken up in a concentration dependent manner, the immune system actively takes up glutamine despite decreased plasma concentrations. Supplementation with glutamine influences uptake by both the gut and the immune system, as evidenced by increased mucosal glutamine concentrations and gut glutathione production. There is evidence suggesting that this improves gut barrier function. Although the benefit of glutamine supplementation is most evident from experimental studies, clinical studies on the effect of glutamine do exist and suggest that glutamine supplementation has beneficial effects with regard to patient outcome.

Effects of parenteral arginine supplementation on the intestinal adaptive response after massive small bowel resection in the rat

BACKGROUND

Arginine (ARG) and its metabolic products (polyamines and nitric oxide) are known to affect gut function and protein synthesis in various tissues. The aim was to study the effect of parenteral ARG supplementation on intestinal adaptation and intestinal function in rats after massive small bowel resection (SBR).

METHODS

Fasted rats (275 g) were studied 24 h after 80% SBR. At t = 6 h, t = 12 h, and t = 18 h after SBR, a 300 mM ARG solution (ARG, n = 9), 5 ml/100 g body weight, was given subcutaneously. Controls received iso-osmolaric amounts of NaCl (NaCl, n = 9) or alanine (ALA, n = 8). Twenty-four hours after operation substrate fluxes across the gut were determined together with intestinal protein synthesis, polyamine concentrations in gut tissue, and gut function by testing intestinal permeability using the urinary recovery of lactulose and rhamnose.

RESULTS

Intestinal fluxes did not differ among groups, except for an increased production of ornithine and a decreased uptake of glutamine after ARG supplementation. Also, intracellular arginine and ornithine concentrations were higher in the jejunum, accompanied by lower concentrations of other amino acids. Intracellular putrescine and gamma-aminobutyric acid, a breakdown product of putrescine, were higher. However, spermidine and spermine were not. Protein synthesis was lower in the ARG group, while intestinal permeability decreased.

CONCLUSIONS

Parenteral arginine supplementation in rats with massive SBR leads to a slowing of intestinal adaptation, indicated by reduced glutamine uptake and protein synthesis. The exact mechanism of this inhibitory effect remains to be elucidated. Intestinal permeability, however, benefits from arginine supplementation, possibly related to better enterocyte differentiation.

Upper gastrointestinal bleeding: an ammoniagenic and catabolic event due to the total absence of isoleucine in the haemoglobin molecule

Upper gastrointestinal bleeding causes increased urea concentrations in patients with normal liver function and high ammonia concentrations in patients with impaired liver function. This ammoniagenesis may precipitate encephalopathy. The haemoglobin molecule is unique because it lacks the essential amino acid isoleucine and has high amounts of leucine and valine. Upper gastrointestinal bleeding therefore presents the gut with protein of very low biologic value, which may be the stimulus to induce a cascade of events culminating in net catabolism. This may influence the function of rapidly dividing cells and short half-life proteins. We hypothesize that, following a variceal bleed in a cirrhotic patient, the lack of isoleucine in blood protein is the cause of the exaggerated ammoniagenesis and catabolism. We propose that intravenous administration of isoleucine may serve as a simple therapeutic that transforms blood protein in a balanced protein, resulting in only a short-lived rise in ammonia and urea production, and preventing interference with protein synthesis.

[Uremia after hemorrhages in the upper digestive tract]

Haemorrhages in the upper GI tract may lead to severe uraemia and, in patients with liver failure, to hyperammonaemia. The cause of this is not yet sufficiently clear. Recently we observed a decrease in arterial isoleucine levels after intragastric blood administration in pigs. This contrasted with elevated levels of most other amino acids, ammonia and urea. After an isonitrogenous control meal in these pigs all amino acids including isoleucine increased, and urea increased to a lesser extent, suggesting a relationship between the arterial isoleucine decrease and uraemia after gastrointestinal (GI) haemorrhage. Analysis of blood protein showed a complete absence of the essential amino acid isoleucine, making it a protein of low biological value. In additional porcine experiments, uraemia after intragastric blood administration could be prevented by simultaneous intravenous isoleucine administration. This led to the hypothesis that there was a causal relationship between the absence of isoleucine in blood protein and the uraemia and hyperammonaemia observed after GI bleeding. Similar results were seen in patients with intact and with impaired liver functions. These results support the hypothesis that the absence of isoleucine in blood protein causes decreased plasma and tissue isoleucine levels after GI haemorrhage. This might inhibit protein synthesis, and may contribute to uraemia and hyperammonaemia in patients with normal and impaired liver function, respectively. Intravenous isoleucine administration after GI haemorrhage could be beneficial.

Renal arginine metabolism in fasted rats with subacute short bowel syndrome

1. Arginine can be produced in the kidney from citrulline. An important source of circulating citrulline is the intestinal breakdown of glutamine. Consequently, partial enterectomy leads to decreased plasma citrulline levels. The aim of the present study was to investigate the effect of diminished arterial citrulline levels on renal arginine production and total-body free arginine pools.2. Renal amino acid metabolism was studied 24 h after 75% small bowel resection in rats fasted overnight (16 h) (n=12; total fast 40 h). Sham-operated (n=9) and non-operated 16-h and 40-h fasted controls were studied in parallel (n=8/n=7). During anaesthesia, L-(2, 3-3H)-arginine and para-aminohippuric acid were infused until steady state. Subsequently, arterial and renal venous blood samples were taken. Concentrations of para-aminohippurate and amino acids and specific activity of arginine and citrulline were measured to calculate renal plasma flow, net renal uptake or release, and unidirectional influx or efflux of arginine and citrulline, as well as whole-body arginine turnover.3. Arterial citrulline was decreased in enterectomized rats compared with sham-operated rats (23+/-3 versus 44+/-6 microM). Net renal citrulline uptake and arginine release were almost stoichiometric (-36+/-7 and 38+/-6 nmol.min-1. 100 g-1 body weight respectively in sham-operated rats) and were both diminished by 50% in enterectomized versus sham-operated rats. In all groups, net renal arginine production accounted for less than 10% of whole-body rate of arginine appearance (488 nmol.min-1.100 g-1 body weight in the sham group). Despite decreased net renal citrulline consumption and renal arginine production in enterectomized rats, whole-body rate of arginine appearance and arterial arginine did not change significantly.4. In conclusion, net renal arginine production is reduced 24 h after 75% enterectomy in fasted rats. However, this does not have important effects on whole-body arginine production.

[Pseudomyxoma peritonei]

Pseudomyxoma peritonei was diagnosed in 3 men aged 38, 66 and 54 years with weight loss and distension of the abdomen. Pseudomyxoma peritonei results from seeding of the peritoneal cavity with mucus-producing epithelium. The disease is traditionally characterized by accumulation of huge amounts of mucinous ascites, relatively long survival and absence of distant, extraperitoneal metastases. Mostly, the primary tumour is an appendicular adenoma or adenocarcinoma. Sometimes, the primary tumor is localized in the ovaries. Extensive surgical debulking with postoperative intraperitoneal chemotherapy appears to be the treatment of choice.

Effects of simulated upper gastrointestinal hemorrhage on ammonia and related amino acids in blood and brain of chronic portacaval-shunted rats

Gastrointestinal (GI) hemorrhage during compromised liver function is known to precipitate portal-systemic encephalopathy (PSE). Hypothetically, the induced hyperammonemia depletes cerebral glutamate pools. To investigate this hypothesis, rats were studied 14 days after portacaval shunt (PCS) or sham surgery (SHAM). Rats received 3 mL bovine erythrocytes or saline at t = 0, 1, 2, and 3h via a previously placed gastrostomy catheter. At t = 0, 2, 4, 6 and 8h arterial blood and at t = 8h cerebral cortex were sampled for determination of ammonia and amino acids. Control rats (NORM) were sampled without previous surgery. Repeated intragastric blood administration increased the already elevated arterial ammonia levels in PCS rats further. This resulted in higher cerebral cortex ammonia and glutamine levels after blood administration. Despite the accumulation of ammonia and glutamine, cerebral cortex glutamate concentrations remained unaltered. Yet, PCS rats became more encephalopathic after blood gavages, suggesting that there is not a clear-cut relation between cerebral cortex glutamate concentrations and degree of PSE. Interestingly, cerebral cortex concentrations of GABA, tyrosine and phenylalanine were markedly increased. Whether these observations are pathogenetically related to PSE remains to be established. The present model of simulated GI hemorrhage in PCS rats seems to be a suitable, clinically valid model for future research regarding hepatic encephalopathy.

Decreased plasma and tissue isoleucine levels after simulated gastrointestinal bleeding by blood gavages in chronic portacaval shunted rats

BACKGROUND

Previously, arterial concentrations of the essential branched chain amino acid isoleucine (Ile) were found to have decreased by more than 50% after gastrointestinal haemorrhage in patients and after intragastric blood administration in healthy humans and pigs. Hypothetically, this induced hypoisoleucinaemia could deplete tissue Ile pools.

AIMS

To study the effect of repeated blood gavages on arterial and tissue Ile levels during normal and impaired liver function.

SUBJECTS

Male Wistar rats.

METHODS

14 days after portacaval shunting or sham surgery, rats received 3 ml bovine erythrocytes or saline at 0, 1, 2, and 3 hours via a gastrostomy catheter in the duodenum. At 0, 2, 4, 6 and 8 hours arterial blood and at 8 hours intestine, liver, muscle, and cerebral cortex were sampled for determination of ammonia and amino acid concentrations.

RESULTS

In both groups repeated blood administration resulted in a marked decrease in plasma Ile (40-60%). This was accompanied by decreased tissue Ile concentrations in liver (50%), muscle (40-60%), and cerebral cortex (40-50%), but unaltered intestinal Ile levels. In contrast, the arterial and tissue concentrations of ammonia, urea, and of most amino acids increased, most strikingly of the other two branched chain amino acids, valine and leucine.

CONCLUSIONS

Simulated gastrointestinal bleeding by blood gavages in rats with and without impaired liver function leads to hypoisoleucinaemia and decreased tissue Ile pools.

Decreased plasma isoleucine concentrations after upper gastrointestinal haemorrhage in humans

BACKGROUND

A decrease in arterial isoleucine values after intragastric blood administration in pigs has been observed. This contrasted with increased values of most other amino acids, ammonia, and urea. After an isonitrogenous control meal in these pigs all amino acids including isoleucine increased, and urea increased to a lesser extent, suggesting a relation between the arterial isoleucine decrease and uraemia after gastrointestinal haemorrhage.

METHODS

To extend these findings to humans, plasma amino acids were determined after gastrointestinal haemorrhage in patients with peptic ulcers (n = 9) or oesophageal varices induced by liver cirrhosis (n = 4) and compared with preoperative patients (n = 106).

RESULTS

After gastrointestinal haemorrhage, isoleucine decreased in all patients by more than 60% and normalised within 48 hours. Most other amino acids increased and also normalised within 48 hours. Uraemia occurred in both groups, hyperammonaemia was seen in patients with liver cirrhosis.

CONCLUSIONS

These results confirm previous findings in animals and healthy volunteers that plasma isoleucine decreases after simulated upper gastrointestinal haemorrhage. This supports the hypothesis that the absence of isoleucine in blood protein causes decreased plasma isoleucine values after gastrointestinal haemorrhage, and may be a contributory factor to uraemia and hyperammonaemia in patients with normal and impaired liver function, respectively. Intravenous isoleucine administration after gastrointestinal haemorrhage could be beneficial and will be the subject of further research.

Prospective evaluation of faecal fatty acid excretion in short bowel syndrome in newborns

Short bowel syndrome (SBS) in the newborn results in limited intestinal absorptive capacity, leading especially to fatty acid (FA) malabsorption. It is unknown whether adaptation occurs in time in FA absorption, and whether this adaptation is chain-length dependent. The aid of the present study was to prospectively evaluate FA absorption and excretion during SBS in the newborn. Twenty-one neonates who underwent small bowel resection (of variable length) for various reasons (necrotizing enterocolitis, intestinal atresia, meconium peritonitis, cloacal extrophy, etc) were studied. Eight neonates had SBS, defined as a small bowel remnant of less than 50% of the original small bowel length related to gestational age. The mean remaining small bowel length in the SBS group was 34% (24% to 42%). The non-SBS control group consisted of 13 neonates who had only minor small bowel resections. The mean remaining bowel length for the non-SBS group was 95% (70% to 100%). The results show that the total fractional excretion of FA (FE-FA) at 2 weeks and 1, 2, 3, and 4 months postsurgery was 51% +/- 37%, 33% +/- 24%, 51% +/- 65%, 53% +/- 27%, and 7% +/- 2% in patients with SBS, versus 12% +/- 8%, 24% +/- 10%, 9% +/- 3%, 8% +/- 3% and 17% +/- 14% in the non-SBS controls, respectively (P < .05 by ANOVA). There appeared to be an amelioration in time in FA absorption, especially in the SBS group, after 3 months. FE-FA was chain-length related, being considerably less for C10 and C12 than for C14 and longer amounts. An amelioration of absorption occurred in the SBS patients, especially with the longer-chain FA. On the basis of the study data, the authors conclude that in the initial adaptation phase shorter chain lengths are better absorbed than longer chain lengths; however, in the latter FA group, substantial adaptation occurs with time.

Supplementation of enteral nutrition with butyrate leads to increased portal efflux of amino acids in growing pigs with short bowel syndrome

Previously, short-chain fatty acids (SCFAs) infused into the hindgut or administered intravenously have been shown to stimulate intestinal adaptation after massive small bowel resection. To study the effects of enterally supplemented n-butyrate on food digestion and absorption in growing pigs with short bowel syndrome, the authors examined the portal efflux of glucose and amino acids during a meal. In 12 growing pigs, 75% of the small intestine was resected. Five control (CONT) animals underwent transection and reanastomosis of the small bowel. A splenic vein, the aorta, the portal vein, and the stomach were catheterized. Postoperatively, seven enterectomized (ENT) pigs and the CONT pigs were fed by infusion of a liquid diet, without SCFAs, through the gastrostomy catheter. Five enterectomized animals received the same diet, supplemented with butyrate (ENTB) (0.26 g/kg body weight/d). After 3 weeks, the portal efflux of amino acids and glucose was measured after 2 hours of constant feeding. The portal efflux of glucose expressed per kilogram of body weight in the ENT group was 10% of that in the CONT group, and in the ENTB group it was 42%. No significant difference in portal glucose efflux between the ENT and the ENTB groups was found. The portal efflux of amino acids during a meal in the ENT group in relation to the CONT groups was 34%; in the ENTB group it was 63%. These data suggest that enteral supplementation with SCFAs leads to improvement of intestinal food digestion and absorption during short bowel syndrome, possibly related to improved intestinal adaptation.

Ammonia and glutamine metabolism during liver insufficiency: the role of kidney and brain in interorgan nitrogen exchange

BACKGROUND

During liver failure, urea synthesis capacity is impaired. In this situation the most important alternative pathway for ammonia detoxification is the formation of glutamine from ammonia and glutamate. Information is lacking about the quantitative and qualitative role of kidney and brain in ammonia detoxification during liver failure.

METHODS

This review is based on own experiments considered against literature data.

RESULTS AND CONCLUSIONS

Brain detoxifies ammonia during liver failure by ammonia uptake from the blood, glutamine synthesis and subsequent glutamine release into the blood. Although quantitatively unimportant, this may be qualitatively important, because it may influence metabolic and/or neurotransmitter glutamate concentrations. The kidney plays an important role in adaptation to hyperammonaemia by reversing the ratio of ammonia excreted in the urine versus ammonia released into the blood from 0.5 to 2. Thus, the kidney changes into an organ that netto removes ammonia from the body as opposed to the normal situation in which it adds ammonia to the body pools.

Influence of storage conditions on normal plasma amino-acid concentrations

Conflicting information in the literature is given concerning the optimal preparation and storage conditions of plasma samples for amino-acid analysis. To assess the optimal pre-storage treatment, we compared several methods and studied their influence on plasma amino-acid levels of rats and humans, stored at different temperatures. In rat plasma, the frequently reported degradation of glutamine was not measurable at a storage temperature of -70 degrees C. However, storage of native, not deproteinised plasma at this temperature, resulted in a 32% decrease of arginine and a 30% increase in ornithine after 24 weeks. Deproteinisation prohibited this arginine decay. At -20 degrees C, arginine decay was even more pronounced, whereas glutamine decreased by 14% in untreated plasma, by 10% in sulfosalicylic acid deproteinised plasma and by 3% if the deproteinisation was followed by removal of the protein pellet and subsequent neutralisation. To confirm these unexpected results in humans, we repeated this experiment with plasma of 6 volunteers. In contrast to rat plasma, we did not observe any changes in arginine and ornithine concentrations in human plasma stored at -70 degrees C. At -20 degrees C the reduction in glutamine was only 4-5%. These results suggest that interspecies differences in enxymatic activity exist in plasma. Finally, having assessed the optimal treatment and storage conditions (deproteinisation followed by storage at -70 degrees C), samples were obtained from a total of 112 human volunteers, stratified for age and sex, and amino-acids were measured. In the female group, we found a tendency to a gradual increase in most amino-acid concentrations with advancing age, which however only reached significance for histidine, citrulline, alanine and leucine. These observations demonstrate that plasma samples for amino-acid analysis should be deproteinised and stored at -70 degrees C. Also important interspecies differences appear to exist in plasma enzymatic activity. Finally, control samples should be taken from an age and sex matched control group.

Muscle ammonia and glutamine exchange during chronic liver insufficiency in the rat

The aim of this study was to investigate the role of skeletal muscle in ammonia and glutamine metabolism during chronic hyperammonemia induced by liver insufficiency. The hindquarter ammonia and amino acid fluxes and muscle tissue concentrations were studied in two rat models of chronic liver insufficiency, portacaval shunting and portacaval shunting plus bile-duct ligation, as well as in sham-operated animals, 7 and 14 days after surgery, and in normal, unoperated rats. To reduce nutritional influences, portacaval-shunted rats and sham-operated rats were pair-fed to portacaval shunt biliary obstruction rats. Arterial ammonia levels were elevated in both liver insufficiency groups. In the portacaval shunting plus bile-duct ligation group, arterial glutamine levels were elevated compared with sham-operated controls. No net hind-quarter ammonia uptake was observed in any of the groups, despite hyperammonemia in the chronic liver insufficiency groups. Hindquarter glutamine release was always increased in the liver insufficiency groups compared with sham-operated controls, despite similar muscle glutamine levels in the sham-operated and hyperammonemic groups, suggesting enhanced muscle glutamine synthesis in the latter groups. Muscle ammonia levels were always increased and muscle glutamate decreased in the hyperammonemic groups, probably indicating glutamate consumption by enhanced glutamine synthesis. The increased phenylalanine tissue concentrations and efflux in portacaval shunt/biliary obstruction rats suggest that enhanced net muscle protein breakdown, amino acid catabolism and transamination, rather than ammonia uptake from the blood furnish amino acids and ammonia for enhanced glutamine synthesis. These experiments suggest that nutritional factors are important in explaining altered muscle metabolism during chronic liver insufficiency.

Effects of methionine sulphoximine treatment on renal amino acid and ammonia metabolism in rats

Renal glutamine metabolism in relation to ammoniagenesis has been extensively studied during chronic metabolic acidosis, when arterial glutamine levels are reduced. However, little is known about the effects of reduced glutamine delivery on renal glutamine and ammonia metabolism at physiological systemic pH values. Therefore, a model of decreased arterial glutamine concentrations at normal pH values was developed using methionine sulphoximine (MSO). Renal glutamine and ammonia metabolism was measured by determining fluxes and intracellular concentrations after an overnight fast in ether anaesthetized normal rats, MSO-treated rats and their pair-fed controls. Moreover, fluxes and intracellular concentrations of several other amino acids were determined concomitantly. After 2 and 4 days of MSO treatment, arterial glutamine concentrations were reduced to 55%, while arterial ammonia concentrations increased by 70%. Kidney glutamine uptake reduced, but systemic pH was unchanged. Fractional extraction of glutamine remained unchanged, suggesting that also in vivo net uptake of glutamine by the kidney at subnormal levels is related to arterial glutamine concentrations. As a result, at day 2 but not at day 4, the kidney reduced the net release of ammonia into the renal vein and thus reduced net renal ammonia addition to body ammonia pools. Therefore at day 2, the kidney seems to play an important role in adaptation to both hyperammonaemia and hypoglutaminaemia.

Renal ammonia and glutamine metabolism during liver insufficiency-induced hyperammonemia in the rat

Renal glutamine uptake and subsequent urinary ammonia excretion could be an important alternative pathway of ammonia disposal from the body during liver failure (diminished urea synthesis), but this pathway has received little attention. Therefore, we investigated renal glutamine and ammonia metabolism in midly hyperammonemic, portacaval shunted rats and severely hyperammonemic rats with acute liver ischemia compared to their respective controls, to investigate whether renal ammonia disposal from the body is enhanced during hyperammonemia and to explore the limits of the pathway. Renal fluxes, urinary excretion, and renal tissue concentrations of amino acids and ammonia were measured 24 h after portacaval shunting, and 2, 4, and 6 h after liver ischemia induction and in the appropriate controls. Arterial ammonia increased to 247 +/- 22 microM after portacaval shunting compared to controls (51 +/- 8 microM) (P < 0.001) and increased to 934 +/- 54 microM during liver ischemia (P < 0.001). Arterial glutamine increased to 697 +/- 93 microM after portacaval shunting compared to controls (513 +/- 40 microM) (P < 0.01) and further increased to 3781 +/- 248 microM during liver ischemia (P < 0.001). In contrast to controls, in portacaval shunted rats the kidney net disposed ammonia from the body by diminishing renal venous ammonia release (from 267 +/- 33 to -49 +/- 59 nmol/100 g body wt per min) and enhancing urinary ammonia excretion from 113 +/- 24 to 305 +/- 52 nmol/100 g body wt per min (both P < 0.01). Renal glutamine uptake diminished in portacaval shunted rats compared to controls (-107 +/- 33 vs. -322 +/- 41 nmol/100 g body wt per min) (P < 0.01). However, during liver ischemia, net renal ammonia disposal from the body did not further increase (294 +/- 88 vs. 144 +/- 101 nmol/100 g body wt per min during portacaval shunting versus liver ischemia). Renal glutamine uptake was comparable in both hyperammonemic models. These results indicate that the rat kidney plays an important role in ammonia disposal during mild hyperammonemia. However, during severe liver insufficiency induced-hyperammonemia, ammonia disposal capacity appears to be exceeded.

Metabolic adaptation of the kidney to hyperammonemia during chronic liver insufficiency in the rat

The aim of this study was to evaluate the role of renal ammonia and glutamine metabolism in the metabolic adaptation to chronic liver insufficiency-induced hyperammonemia in the rat. To this purpose, urinary excretion, renal net exchange and tissue concentrations of ammonia and amino acids were measured in anesthetized, normal control rats that did not undergo surgery, in control rats that underwent sham surgery, in rats that underwent portacaval shunting and in rats that underwent both portacaval shunting and bile duct ligation. Rats that underwent sham surgery and portacaval shunting were pair-fed with rats that underwent portacaval shunting and biliary obstruction, to correct for anorexia in that group, and all rats that were operated on were studied 7 and 14 days after surgery. Arterial ammonia and glutamine levels were elevated in groups that underwent portacaval shunting and portacaval shunting plus biliary obstruction at all time points. At days 7 and 14, total renal ammonia production decreased in rats that underwent portacaval shunting and in rats that underwent portacaval shunting plus biliary obstruction, associated with a 50% decrease in net renal glutamine uptake and strongly diminished net ammonia release into the renal vein, which was most prominent in the group that underwent portacaval shunting plus biliary obstruction. Urinary ammonia excretion was similar in rats that underwent portacaval shunting and in those that underwent sham surgery but was increased more than 200% at days 7 and 14 in rats that underwent portacaval shunting plus biliary obstruction. In this group, in contrast to portacaval-shunted rats, the kidney appeared to be an organ of net ammonia disposal from the body. In separate experiments in unanesthetized, unrestrained rats, similar changes in urinary ammonia excretion were observed without changes in arterial pH, excluding an effect of anesthesia or pH on the obtained results. These results indicate that the kidney plays an important role in the metabolic adaptation to hyperammonemia during chronic liver insufficiency in the rat.

Intestinal glutamine and ammonia metabolism during chronic hyperammonaemia induced by liver insufficiency

During liver insufficiency, besides portasystemic shunting, high arterial glutamine concentrations could enhance intestinal glutamine consumption and ammonia generation, thereby aggravating hyperammonaemia. To investigate this hypothesis, portal drained viscera (intestines) fluxes and jejunal tissue concentrations of ammonia and glutamine were measured in portacaval shunted rats with a ligated bile duct, portacaval shunted, and sham operated rats, seven and 14 days after surgery, and in normal unoperated controls. Effects of differences in food intake were minimised by pair feeding portacaval shunted and sham operated with portacaval shunted rats with biliary obstruction. At both time points, arterial ammonia was increased in the groups with liver insufficiency. Also, arterial glutamine concentration was raised in all operated groups compared with normal unoperated controls. At both time points, ammonia production by portal drained viscera was reduced in portacaval shunted rats with biliary obstruction, portacaval shunted, and sham operated rats compared with normal unoperated controls, and no major differences were found between these operated groups. At day 7 in all operated groups glutamine uptake by portal drained viscera was lower than in normal unoperated controls, but no major differences were found at day 14. These experiments show that ammonia generation by portal drained viscera remains unchanged in rats with chronic liver insufficiency despite alterations in arterial glutamine concentrations and intestinal glutamine uptake. The hyperammonaemia seems to be mainly determined by the portasystemic shunting.

Cerebral cortex ammonia and glutamine metabolism in two rat models of chronic liver insufficiency-induced hyperammonemia: influence of pair-feeding

Enhanced cerebral cortex ammonia uptake, subsequent glutamine synthesis, and glutamine release into the bloodstream have been hypothesized to deplete cerebral cortex glutamate pools. We investigated this hypothesis in rats with chronic liver insufficiency-induced hyperammonemia and in pair-fed controls to rule out effects of differences in food intake. Cerebral cortex plasma flow and venous-arterial concentration differences of ammonia and amino acids, as well as cerebral cortex tissue concentrations, were studied 7 and 14 days after surgery in portacaval-shunted/bile duct-ligated, portacaval-shunted, and sham-operated rats, while the latter two were pair-fed to the first group, and in normal unoperated ad libitum-fed control rats. At both time points, arterial ammonia was elevated in the chronic liver insufficiency groups and arterial glutamine was elevated in portacaval shunt/biliary obstruction rats compared to the other groups. In the chronic liver insufficiency groups net cerebral cortex ammonia uptake was observed at both time points and was accompanied by net glutamine release. Also in these groups, cerebral cortex tissue glutamine, many other amino acid, and ammonia levels were elevated. Tissue glutamate levels were decreased to a similar level in all operated groups compared with normal unoperated rats, irrespective of plasma and tissue ammonia and glutamine levels. These results demonstrate that during chronic liver insufficiency-induced hyperammonemia, the rat cerebral cortex enhances net ammonia uptake and glutamine release. However, the decrease in tissue glutamate concentrations in these chronic liver insufficiency models seems to be related primarily to nutritional status and/or surgical trauma.

Partial enterectomy in the rat does not diminish muscle glutamine production

The hypothesis was posed that consumption of the amino acid glutamine by the splanchnic tissues is an important regulating mechanism for its production in muscle. Therefore, glutamine consumption or production in portal-drained viscera (PDV), liver, and hindquarter was measured by determining fluxes and intracellular concentrations after 80% enterectomy or SHAM operation in rats. Moreover, fluxes and intracellular concentrations of several other amino acids, ammonia, and liver urea production were determined concomitantly. After enterectomy, arterial glutamine concentration was increased, PDV glutamine consumption was decreased by 77%, and liver glutamine consumption was unchanged compared with values in SHAM-operated rats. Although hindquarter glutamine production remained unchanged after enterectomy, intracellular glutamate concentration (glutamine precursor) was lower, suggesting that enterectomy induces changes in muscle metabolism without changing the flux of glutamine. For the remaining gut, it was calculated that after enterectomy glutamine consumption per gram remaining gut tissue increased. These results cast doubt on the hypothesis that diminished splanchnic glutamine uptake can reduce muscle glutamine production.

Cerebral cortex ammonia and glutamine metabolism during liver insufficiency-induced hyperammonemia in the rat

Hyperammonemia has been suggested to induce enhanced cerebral cortex ammonia uptake, subsequent glutamine synthesis and accumulation, and finally net glutamine release into the blood stream, but this has never been confirmed in liver insufficiency models. Therefore, cerebral cortex ammonia- and glutamine-related metabolism was studied during liver insufficiency-induced hyperammonemia by measuring plasma flow and venous-arterial concentration differences of ammonia and amino acids across the cerebral cortex (enabling estimation of net metabolite exchange), 1 day after portacaval shunting and 2, 4, and 6 h after hepatic artery ligation (or in controls). The intra-organ effects were investigated by measuring cerebral cortex tissue ammonia and amino acids 6 h after liver ischemia induction or in controls. Arterial ammonia and glutamine increased in portacaval-shunted rats versus controls, and further increased during liver ischemia. Cerebral cortex net ammonia uptake, observed in portacaval-shunted rats, increased progressively during liver ischemia, but net glutamine release was only observed after 6 h of liver ischemia. Cerebral cortex tissue glutamine, gamma-aminobutyric acid, most other amino acids, and ammonia levels were increased during liver ischemia. Glutamate was equally decreased in portacaval-shunted and liver-ischemia rats. The observed net cerebral cortex ammonia uptake, cerebral cortex tissue ammonia and glutamine accumulation, and finally glutamine release into the blood suggest that the rat cerebral cortex initially contributes to net ammonia removal from the blood during liver insufficiency-induced hyperammonemia by augmenting tissue glutamine and ammonia pools, and later by net glutamine release into the blood. The changes in cerebral cortex glutamate and gamma-aminobutyric acid could be related to altered ammonia metabolism.

A simple new method for repeated in vivo cerebral cortex flux measurement in rats

A new application of an indicator dilution technique, using nonradioactive para-aminohippuric acid, is described for superior sagittal sinus blood flow determination in rats. Superior sagittal sinus blood flow, mainly representing cerebral cortex blood flow, amounted to 541 +/- 49 microliters/min in ketamine-anesthetized, but otherwise normal, rats breathing room air. Increasing arterial pCO2 enhanced superior sagittal sinus blood flow (P less than 0.01), providing evidence that this method correctly measures cerebral blood flow. The respiratory quotient was 1.1 and the cerebral cortex metabolic rate of oxygen consumption was +/- 1.45 mumol/min. Cerebral cortex ammonia uptake was not significantly different from zero and of the amino acid fluxes, only alanine differed from zero (P less than 0.05). Flux measurements are crucial in studies of healthy or altered organ metabolism in both experimental animals and postoperative surgical patients. We devised a simple and economical method of repeated cerebral cortex flux measurement in rats that is a potentially valuable tool in metabolic studies of the cerebral cortex.

Altered glutamine metabolism in rat portal drained viscera and hindquarter during hyperammonemia

In normal rats, muscle is the major glutamine releasing organ and gut is the major glutamine consuming organ. It has been suggested that enhanced muscle ammonia detoxification and gut ammonia production occurs during liver insufficiency-induced hyperammonemia. Therefore, ammonia and amino acid fluxes across portal-drained viscera and hindquarter, and muscle concentrations were measured in portacaval shunted and acute liver ischemia rats. Arterial ammonia and most amino acids were increased after portacaval shunting and increased progressively during liver ischemia, but net hindquarter ammonia uptake was not observed. Net hindquarter glutamine efflux was increased during portacaval shunting, but it decreased during liver ischemia, while muscle glutamine concentrations increased. The comparable net portal drained viscera glutamine uptake in normal and portacaval shunted rats changed during liver ischemia from net uptake to release, coinciding with release of most other amino acids. These results cast doubt on the ammonia detoxifying role of muscle during acute liver ischemia-induced hyperammonemia in the rat. The portal drained viscera glutamine release during severe hyperammonemia could be due to intestinal damage.