Hepatocyte ultrastructure in rats with portacaval shunt

The principal reported morphological consequence of portacaval shunt in the rat is liver atrophy. The present study was designed to investigate ultrastructural changes in hepatocytes using electron microscopy morphometry. Two weeks following portacaval shunt, rat livers were fixed by perfusion and hepatocyte organelles from the two opposite zones of the acinus (zones 1 and 3) were quantified. Liver weight/body weight decreased by 50%, hepatocyte-specific volume decreased by 30% (28% in zone 1 and 35% in zone 3). Estimated sinusoidal space increased, and estimated number of hepatocytes decreased by 50%. Hepatocytes had a normal ultrastructure except for mitochondria. Smooth endoplasmic reticulum-specific surface area was reduced by 65% (zone 3), and rough endoplasmic reticulum surface density was increased in zone 1 only. Mitochondriaspecific volume was unchanged but decreased inner and outer membrane-specific surface area in zone 3 suggests in this zone a change in their conformation and possibly their number. Golgi-rich area surface density increased but not significantly. Hepatocyte loss and atrophy and rearrangement of organelles represent a new ultrastructural steady state following portacaval shunt that may help explain the new functional steady state.     

The effect of arterialization of the liver on gastric secretion of dogs with portacaval shunts

Summary Arterialization of the liver in dogs with portacaval shunts and Heidenhain pouches did not reduce the hypersecretion that usually occurs following the establishment of a portacaval shunt alone.The work described here was supported by the Donald J. Cowling and Jay and Rose Phillips Fund for Surgical Research and the U.S.P.H.S. Peptic Ulcer Grant A-2150.     

Hepatic reticuloendothelial function in rats with various portasystemic shunts and total liver arterialization

Hepatic reticuloendothelial function was measured in 6 experimental groups of rats with various portasystemic shunts or total liver arterialization by computer calculation of the hepatic uptake rate of intravenously injected 99mTc-sulphur colloid. Marked reduction of the hepatic reticuloendothelial system (RES) function was found both 1 and 3 weeks after the construction of a mesentericocaval or conventional end-to-side portacaval shunt. Hepatic RES function was also lowered both 1 and 3 weeks after a modified portacaval shunt, but the reduction was much less pronounced. Total liver arterialization produced a similar mild reduction of hepatic RES function after 1 week; however, there was no longer any significant reduction after 3 weeks. This study concludes that total liver arterialization ameliorates the negative effect that portasystemic shunting has on hepatic RES function.     

Effect of portal arterialization on hepatic cytochrome P-450 in rats with portacaval shunt.

Fractional clearance of colloidal gold particles (k), liver weight and hepatic cytochrome P-450 were measured in rats with portacaval shunt and in rats with portacaval shunt plus arterialization of the hepatic stump of the portal vein. The effects of enzyme induction by phenobarbital was studied in both groups. Total arterialization of the liver provides a probably normal hepatic blood flow and seems to protect the liver from post-shunt atrophy. Nevertheless, in both arterialized and shunted rats, the cytochrome P-450 concentration was significantly lower than in controls. The same results were obtained after treatment by phenobarbital. These findings suggest that normal hepatic blood flow and oxygen supply are not the main determinant of a normal activity of the hepatic microsomal biotransformation system. Substances present in portal blood would probably be necessary in maintaining hepatic cytochrome P-450 level.     

Liver glycogen after portacaval shunt in rats

Theories to explain the metabolic effects of portacaval shunt (PCS) have frequently failed to take into account the sequelae of PCS-induced anorexia. In this study PCS rats, followed up to 42 days postoperatively, had a lower food intake than ad libitum-fed (ALC) controls and also lost 10% body wt compared to a 20% gain of ALC rats. Liver weight was significantly reduced in PCS rats compared to ALC rats, pair-fed sham-operated (S) and pair-fed normal control (PFC) rats. However, liver glycogen was equally reduced in all animals with reduced food intake (PCS, S, and PFC rats) compared to ALC rats. Plasma glucose was significantly lower in PCS rats and PCS rats had markedly elevated plasma glucagon and lower plasma insulin concentrations than ALC rats, with the result that they had a low insulin: glucagon molar ratio of 1.3:1 compared to 10.2:1 in the ALC rats. The pair-fed control groups had intermediate I:G ratios and plasma glucose concentrations, thus an inverse relationship between mean plasma glucose and mean I:G ratio for each group was found, suggesting that the blood glucose concentration was the primary event determining the I:G ratio for each group.These controlled experiments indicate that hepatic atrophy after PCS appears to be directly related to the shunting of portal blood away from the liver, while reduced liver glycogen is related to decreased food intake. Reduction in total body weight, relative hypoglycemia, and elevated I:G ratios appear to be due to a combination of factors.     

Inflammation and hepatic encephalopathy: ibuprofen restores learning ability in rats with portacaval shunts

One of the neurological alterations in patients with minimal or overt hepatic encephalopathy is cognitive impairment. This impairment is reproduced in rats with chronic liver failure due to portacaval shunt (PCS). These rats show decreased ability to learn a conditional discrimination task in a Y-maze, likely due to reduced function of the glutamate-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway in brain. It has been proposed that inflammation exacerbates the neuropsychological alterations induced by hyperammonemia, suggesting that inflammation-associated alterations may contribute to cognitive impairment in hepatic encephalopathy. This study assessed whether treatment with an anti-inflammatory drug, ibuprofen, is able to restore the function of the glutamate-NO-cGMP pathway in cerebral cortex in brain in vivo and/or learning ability in PCS rats. We show that PCS rats have increased levels of interleukin-6 and increased activities of cyclooxygenase and of inducible NO synthase in cerebral cortex, indicating the presence of inflammation. Chronic treatment with ibuprofen normalizes cyclooxygenase and inducible NO synthase activities but not interleukin-6 levels. Moreover, ibuprofen normalizes the function of the glutamate-NO-cGMP pathway in cerebral cortex in vivo and completely restores the ability of rats with chronic liver failure to learn the Y-maze task. This supports that inflammation contributes to the cognitive impairment in hepatic encephalopathy. CONCLUSION: the results reported point to the possible therapeutic utility of decreasing inflammation in the treatment of the cognitive deficits in patients with minimal or overt hepatic encephalopathy.     

Oral administration of sildenafil restores learning ability in rats with hyperammonemia and with portacaval shunts

Patients with liver disease with overt or minimal hepatic encephalopathy show impaired intellectual capacity. The underlying molecular mechanism remains unknown. Rats with portacaval anastomosis or with hyperammonemia without liver failure also show impaired learning ability and impaired function of the glutamate-nitric oxide-cyclic guanine monophosphate (glutamate-NO-cGMP) pathway in brain. We hypothesized that pharmacological manipulation of the pathway in order to increase cGMP content could restore learning ability. We show by in vivo brain microdialysis that chronic oral administration of sildenafil, an inhibitor of the phosphodiesterase that degrades cGMP, normalizes the function of the glutamate-NO-cGMP pathway and extracellular cGMP in brain in vivo in rats with portacaval anastomosis or with hyperammonemia. Moreover, sildenafil restored the ability of rats with hyperammonemia or with portacaval shunts to learn a conditional discrimination task. In conclusion, impairment of learning ability in rats with chronic liver failure or with hyperammonemia is the result of impairment of the glutamate-NO-cGMP pathway. Moreover, chronic treatment with sildenafil normalizes the function of the pathway and restores learning ability in rats with portacaval shunts or with hyperammonemia. Pharmacological manipulation of the pathway may be useful for the clinical treatment of patients with overt or minimal hepatic encephalopathy.     

Inhibition of aromatase improves nutritional status following portacaval anastomosis in male rats

BACKGROUND/AIMS: The portacaval anastamosis (PCA) rat is a model of the nutritional and endocrine consequences of liver cirrhosis. We hypothesized that failure to gain body weight in the PCA rat was the consequence of low testosterone levels and will be reversed by 4-hydroxyandrostenedione, a specific aromatase inhibitor. METHODS: Male Sprague-Dawley rats subjected to an end-to-side PCA or sham surgery were administered either 4-hydroxyandrostenedione or vehicle. Food intake, food efficiency, and body weight were measured, animals sacrificed 3 weeks after surgery, visceral organs harvested and plasma sex steroids measured. Hepatic RNA was extracted and dot blots done to quantify the expression of sex hormone dependent enzymes 16alpha hydroxylase and 15beta hydroxylase. RESULTS: Growth, food intake, food efficiency and plasma testosterone were lower and plasma estradiol higher in PCA than sham rats. Hepatic expression of testosterone driven 16alpha hydroxylase was lower and estradiol driven 15beta hydroxylase higher in PCA rats. These alterations were reversed by 4-hydroxyandrostenedione. CONCLUSIONS: These observations demonstrate that use of aromatase inhibitor reverses the nutritional and endocrine abnormalities in the PCA rat and suggest that this approach may be useful in cirrhotic patients.     

Comparison of portacaval shunts in patients with alcoholic and nonalcoholic liver disease

A series of 46 patients with alcoholic and nonalcoholic cirrhosis and who underwent portasystemic decompressive procedures were analyzed and compared. The two groups were similar in age and degree of dysfunction according to liver function tests and functional classification. For both emergency and elective procedures operative mortality was significantly less in the nonalcoholic group: For emergency procedures it was 20% in the nonalcoholic group, 57% in the alcoholic; for elective procedures it was 5.3% in the nonalcoholic, 20% in the alcoholic. Long-term survival and frequency of severe encephalopathy were nearly the same for both groups although 60-year-old or older nonalcoholics did better, with no operative deaths and only 1 case of severe encephalopathy. The older patients with alcoholic cirrhosis faired poorly—4 of 5 died of hepatic failure, 2 during the operative period. Three patients had active chronic hepatitis and cirrhosis. One died during the operative period; the other 2 have suffered from chronic encephalopathy requiring continuous medical therapy for control.At the VA Hospital Woodard is a Research and Education Trainee in Gastroenterology and Webster is a Medical Investigator.     

Short-term administration of parenteral glucose-lipid mixtures improves protein kinetics in portacaval shunted rats

The efficacy of various total parenteral nutrition regimens administered for 72 h in supporting the rat after portacaval anastomosis was evaluated. All animals that received amino acid-containing formulas had significantly improved nitrogen balance (p less than 0.05), albumin synthetic rates (p less than 0.05), and serum albumin concentration (p less than 0.05) compared with animals receiving dextrose only. Rats that received the mixed-fuel system containing amino acids, dextrose, and lipid had significantly improved leucine flux and whole body protein synthesis (p less than 0.05) compared with animals that received dextrose only, or amino acids and dextrose. Diets composed of dextrose only, amino acids and dextrose, or amino acids and dextrose with the addition of currently available long-chain triglyceride lipid emulsion induced abnormal morphologic changes in the liver. No hepatic morphologic changes were evident in rats that received an isocaloric mixed-fuel regimen containing medium- and long-chain triglycerides. The results suggest that mixed-fuel systems containing amino acids and dextrose with lipids are superior to formulas containing dextrose only, or dextrose with amino acids. The improved liver morphology observed in animals given the lipid emulsion system containing medium- and long-chain triglycerides suggests that medium-chain triglycerides may provide an additional benefit in supporting the patient with liver dysfunction.     

Enhanced hyperplasia of gastric enterochromaffinlike cells in response to omeprazole-evoked hypergastrinemia in rats with portacaval shunts. An immunocytochemical and chemical study

The histamine-storing enterochromaffinlike cells, which are numerous in the oxyntic mucosa of the rat stomach, are known to proliferate in response to long-lasting hypergastrinaemia. In addition, portacaval shunting, which is not associated with elevated serum gastrin, causes an increase in enterochromaffinlike cell density. The present study shows that the combination of portacaval shunting and omeprazole-evoked, long-lasting hypergastrinemia results in enhanced enterochromaffinlike cell hyperplasia despite the fact that the hypergastrinemia was not significantly greater than in intact omeprazole-treated rats. The mechanism behind the enhanced response to gastrin of the enterochromaffinlike cells in rats with portacaval shunts is unknown. When results from untreated and omeprazole-treated rats were plotted, there was a linear correlation between the serum gastrin concentration and the enterochromaffinlike cell density in both sham-operated rats and rats with portacaval shunts. We conclude that gastrin plays a role in the development of enterochromaffinlike cell hyperplasia following omeprazole treatment in rats with portacaval shunts but that other as yet unidentified agents may also promote the response.     

Hypertrophy of biliary epithelium in rats with portacaval shunt

Bile ducts of rats with 3-month-old portacaval shunt were shown by light microscopy to present hypertrophy of the biliary epithelium. This hypertrophy could be linked to the increased hepatic arterial flow following portacaval shunt.     

Lipoprotein catabolism in rats with portacaval anastomosis on various diets

The catabolism of lipoproteins was measured in rats with a portacaval anastomosis and in intact control rats. Radioiodinated rat high density lipoproteins or human low density lipoproteins, the major cholesterol-bearing lipoproteins in rat or man respectively, were injected intravenously into rats. More than 90% of trace amounts of these lipoproteins were removed from plasma of rats with portacaval anastomosis and controls on standard chow at closely similar rates within 24 h. Also, [125I]high density lipoproteins left the plasma at comparable rates in controls and rats with portacaval anastomosis, whether fed with a cholesterol-free chow or a carbohydrate-rich lard chow. These dietary regimens were employed to avoid artifacts through a different development of the body weight in operated and control rats. A standard laboratory chow ad libitum led to weight loss in rats with portacaval anastomosis. Pair-fed with a cholesterol-free chow both groups of rats kept the same weight, but only with a carbohydrate-rich lard chow could the natural weight gain be achieved. In all rats with portacaval anastomosis liver weights were reduced and serum cholesterol decreased by 21-31% with the major change in high density lipoproteins. The findings suggest that cholesterol concentrations are not likely to be lowered in rats with portacaval anastomosis by enhanced lipoprotein catabolism.     

Liver ultrastructure in Gilbert's syndrome.

Electron microscopy of hepatic tissue obtained by percutaneous needle biopsy from nine patients with Gilbert's syndrome has revealed in every case gross hypertrophy of hepatocyte agranular endoplasmic reticulum but no other important abnormality. While this may have relevance to impairment of microsomal enzyme activity controlling bilirubin conjugation within liver cells, the serum bilirubin levels in all nine patients were below that normally associated with demonstrable UDP-glucuronyl transferase deficiency. Gross hypertrophy of agranular endoplasmic reticulum may be, therefore, a constant feature of this form of Gilbert's syndrome and may have some diagnostic value in the investigation of unconjugated hyperbilirubinaemia.     

Liver regeneration following portal blood arterialization and splenectomy in acute hepatic failure

BACKGROUND/AIMS: The purpose of the experiment was to estimate an influence of portal blood arterialization in animals with tetrachloromethane-induced acute hepatic failure. METHODOLOGY: Thirty-five pigs were divided into four groups: three groups of 10 and a control group of 5 animals. On day 1 of the experiment an intraperitoneal dose of 477 mg CCl4//kg body wt. in a suspension of corn oil was given to the trial groups to induce an acute hepatic failure. On day 3 after the intoxication all animals were operated on. Aortovenous splenic anastomosis without splenectomy, aorto-venous splenic anastomosis with splenectomy, and splenectomy procedure alone, were performed in groups I, II, and III, respectively. In the control group only laparotomy was performed. Histopathologic estimation of hematoxylin- and eosin-stained specimens and immunohistochemical analysis of regenerating hepatocytes by applying monoclonal serum for CK19, CD56, CD117 were carried out. RESULTS: Liver biopsies demonstrated no quantitative differences concerning the surface of damaged lobules between groups I, II, and III. The phenomenon of parenchyma regeneration was observed in both groups (with and without splenectomy procedure performed). Small stem cells could be observed mainly in the central part of lobules. The immunohistochemical analysis showed that part of the regenerating cells had CD56 and CD117 antigens' receptors, demonstrating no expression of antigen CK19. In the third group of animals (splenectomy without blood arterialization) neither the phenomenon of parenchyma regeneration nor the presence of cells of hepatoblast phenotype were observed. CONCLUSIONS: The arterialization of portal blood in pigs with acute hepatic failure triggered off the regeneration of damaged parenchyma through the colonization of impaired areas of lobules by small stem cells. The lack of the receptor for antigen CK19 could mean that the cells do not originate in bile duct epithelium.     

Efficient hepatic uptake of chylomicron remnant cholesterol in rats with a portacaval anastomosis

Portacaval-shunted and sham-operated male rats, fed ad libitum and of similar weight, were studied 2-3 weeks after surgery. At this time serum cholesterol levels did not differ significantly between the two groups, whereas serum triacylglycerols and phospholipids were lower in the shunted group. These animals also showed an increased serum bile acid level and an increased serum estradiol to testosterone ratio. The metabolism of native chyle labeled with [3H]cholesterol and [14C]linoleic acid or of preformed chylomicron remnants with the same labeling was studied in the groups of rats. Ten minutes after intravenous injection of chylomicron remnants 10.6 +/- 0.5% (means +/- SEM, n = 8) of the injected [3H]cholesterol and 7.6 +/- 0.4% of the [14C]linoleic acid were found per 1 g liver in the portacaval-shunted rats; the corresponding figures in the sham-operated group (n = 8) were 6.4 +/- 0.4 and 4.9 +/- 0.3, respectively (p less than 0.001 for both 3H and 14C). Thus, despite a greater than 40% reduction of liver weight induced by the shunting procedure, the total liver uptake of chylomicron remnants was not significantly decreased. The uptake of chylomicron lipids per unit liver weight was normal in the atrophic livers of portacaval-shunted rats also when very large loads of chyle were administered.