Effect of splenectomy on hepatic regeneration in rats

The effect of splenectomy on hepatic regeneration after partial hepatectomy was investigated in splenectomized and non-splenectomized rats. The results were as follows: The liver weight per body weight after partial hepatectomy increased significantly at 2 and 4 days in splenectomized group compared with non-splenectomized one. The rates of 3H-thymidine uptake in the regenerating liver cells at 24 hours after partial hepatectomy were more enhanced in splenectomized group than in non-splenectomized one. Thymidine kinase activity of the regenerating liver at 24 hours after partial hepatectomy in splenectomized rats was significantly higher than those in non-splenectomized rats. Both mitotic indices and labeling indices at 24 hours after partial hepatectomy in splenectomized rats were significantly higher than those in non-splenectomized group. The cells of mitotic stage were distributed mainly periportal area. From those results, it is suggested that the spleen has some inhibitory factors on hepatic regeneration after partial hepatectomy.     

Liver regeneration in rats treated with the antiandrogen flutamide

Previous studies have shown that male rat liver undergoes demasculinization during hepatic regeneration after partial hepatectomy. In the present study the effect of the antiandrogen flutamide on liver regeneration was assessed. Adult male Wistar rats were treated with flutamide (2 mg/rat/day or 5 mg/rat/day subcutaneously) or vehicle for 3 days prior to and daily after partial hepatectomy. Rates of DNA and polyamine synthesis were assessed by measuring thymidine kinase and ornithine decarboxylase activities, respectively. The rate of liver growth after partial hepatectomy in the three groups was similar at all time points examined. The increases in thymidine kinase activity and ornithine decarboxylase activity after partial hepatectomy were comparable throughout the study. Thus, administration of flutamide did not influence the regenerative response after partial hepatectomy.     

Liver Regeneration in Rats Treated with the Antiandrogen Flutamide

Previous studies have shown that male rat liver undergoes demasculinization during hepatic regeneration after partial hepatectomy. In the present study the effect of the antiandrogen flutamide on liver regeneration was assessed. Adult male Wistar rats were treated with flutamide (2 mglratl day or 5 mglratlday subcutaneously) or vehicle for 3 days prior to and daily after partial hepatectomy. Rates of DNA and poly amine synthesis were assessed by measuring thymidine kinase and ornithine decarboxylase activities, respectively. The rate of liver growth after partial hepatectomy in the three groups was similar at all time points examined. The increases in thymidine kinase activity and ornithine decarboxylase activity after partial hepatectomy were comparable throughout the study. Thus, administration of flutamide did not influence the regenerative response after partial hepatectomy     

Inhibition of hepatic DNA synthesis after partial hepatectomy in the rats with obstructive jaundice with special reference to the enhancement of hepatic protein synthesis

We studied the liver regeneration after partial (68%) hepatectomy in rats with obstructive jaundice followed by the relief of obstruction. Rats received bile duct ligation, then 5 or 14 days later choledocho-duodenostomy was performed. Partial hepatectomy was done at various intervals after the relief of obstruction. DNA synthesis of the regenerating liver, hepatic protein synthesis and mitochondrial swelling induced by exogenous phospholipase A2 (PLA2) were determined. Hepatic DNA synthesis was significantly inhibited in obstructive jaundiced rats compared to controls. While the inhibition disappeared 5 days after the relief of obstruction in 5-day-obstructed group, it was still detectable as late as 21 days after the drainage in 14-day-obstructed group. Hepatic protein synthesis was markedly increased by obstructive jaundice, and this increase continued until 10 days after drainage in 14-day-obstructed group. Partial hepatectomy also increased the hepatic protein synthesis significantly in normal rats, but failed to show any significant changes in obstructive jaundiced rats. Any difference could not be found in PLA2-induced hepatic mitochondrial swelling between obstructive jaundiced rats and normal rats. We concluded the preceding energy-requiring responses in obstructive jaundiced liver resulted in the reduction of hepatic DNA synthesis and in the lack of additional increase of hepatic protein synthesis as the responses to a further insult of partial hepatectomy.     

Effect of activation of the reticuloendothelial system on hepatocyte regeneration in partially hepatectomized rats

Enhanced effect on rat hepatocyte regeneration through activation of the reticuloendothelial system (RES) was investigated. RES was activated using by OK-432 and the phagocytic activity (K-value) increased 2-fold over control rats 24 hours after intraperitoneal injection of OK-432. In OK-432 treated rats, the amount of cyclic AMP in the regenerating liver also increased 1.5-fold higher than in control rats 14 hours after hepatectomy. After 70% partial hepatectomy, liver DNA synthesis in OK-432 treated rats increased 2 to 5-fold higher than in control rats. There was a good correlation between the K-value before hepatectomy and DNA synthesis 24 hours after hepatectomy (r = 0.96). Therefore the RES is one of the most important regulatory factors in liver regeneration. Augmentation of RES before hepatectomy may prevent hepatic failure after resection in liver diseases.     

Beneficial effects of prostaglandin E(1) incorporated in lipid microspheres on liver injury and regeneration after 90% partial hepatectomy in rats

The aim of this study was to assess how the administration of prostaglandin E(1) incorporated in lipid microspheres (Lipo PGE(1)) affects liver injury and regeneration after massive hepatectomy in rats. Two hundred and eight male Wistar rats underwent 90% partial hepatectomy. Lipo PGE(1) of 1, 10 or 30 microg/kg were administered intraperitoneally at 6 h prior to and 0 and 6 h after hepatectomy. Postoperative increases in serum GOT, total bilirubin, IL-6 and plasma endotoxin levels were significantly suppressed by Lipo PGE(1). The depressed phagocytic index and arterial ketone body ratio and hepatic DNA synthesis after 90% partial hepatectomy were significantly enhanced by Lipo PGE(1), which resulted in the improvement of survival. Lipo PGE(1) might bring about a protective effect on liver injury and an enhancement of liver regeneration after massive hepatectomy.     

Cyclic AMP- and ATP-mediated stimulation of DNA synthesis following partial hepatectomy by prostaglandin-E1 in D-galactosamine injured liver

D-galactosamine (D-gal) damaged rats were infused with Prostaglandin E1 (PGE1) through a peripheral vein for 40 min. before and after partial hepatectomy. DNA synthesis following 68% partial hepatectomy was severely inhibited by the pretreatment of D-galactosamine. PGE1 infusion (0.5, 1.0 microgram/kg/min) enhanced the DNA synthesis inhibited by D-gal 600 mg/kg significantly (p less than 0.01). After 20 min. of PGE1 infusion cyclic AMP levels of liver tissue was increased as compared with saline infusion in D-gal (600 mg/kg)-damaged rat (p less than 0.05). Also 20 min. and 3 hour after partial hepatectomy. ATP levels of liver tissue was enhanced in PGE1 treated group (p less than 0.05). However the doses of PGE1 infused in this investigation could not increase the hepatic tissue blood flow measured by hydrogen gas clearance method. These results suggest that PGE1 enhance DNA synthesis of injured liver after partial hepatectomy by the mechanism which PGE1 stimulate cyclic AMP production and increase ATP level in hepatic tissue.     

hGH对肝部分切除术后促进肝再生的动物实验研究

目的 寻求促进肝细胞再生的有效药物。方法 采用形态计量技术,^3H-TdR活体掺入实验以及动脉血酮体比率的变化来观察重组生长激素（hGH)对肝再生的作用。结果 实验组肝切除术后肝细胞核分裂指数、肝细胞核体积密度、新生肝细胞数目密度、动脉血酮体比率及^3H-TdR活体掺入实验结果均显著高于对照组（P＜0．05或P＜0．01）。结论 hGH以大鼠肝部分切除术后残肝有促进其再生的作用。     

Changes in the levels of lipid peroxides in regenerating rat liver and the effect of pretreatment with CoQ10

The present study was undertaken to determine whether CoQ10 pretreatment could modify cellular free radical metabolism in regenerating rat liver and enhance hepatic DNA synthesis. Male Wistar rats (250-300 g) were used. Partial 70% hepatectomy was performed according to Higgins and Anderson. CoQ10 (6 mg/kg body weight) and its solvent as a placebo were injected intravenously 1 hour before operation. Twenty-four hours or 48 hours after 70% hepatectomy resulted in 55% or 50% decreases of hepatic ATP, and marked decreases of endogenous CoQ homologs (CoQ9 and CoQ10), alpha-tocopherol and reduced glutathione (GSH) in remnant liver and was accompanied by 2.5-fold increases in lipid peroxides. However, in CoQ10-treated animals synthesis of ATP was accelerated after 48 hours after partial hepatectomy. There were no changes in the levels of CoQ9, alpha-tocopherol, or GSH or in the level of the enhanced CoQ10 in regenerating liver. The pretreatment also completely suppressed the elevation of lipid peroxide. Moreover, CoQ10 administration markedly increased hepatic DNA synthesis at 48 hours after partial hepatectomy. These results indicate that cellular damage during hepatic regeneration is in part due to lipid peroxidation, and suggest that CoQ10 is effective in the pretreatment of liver resection.     

Changes in hepatic venous oxygen saturation related to the extent of regeneration after partial hepatectomy in rats

BACKGROUND: Changes in hepatic oxygen metabolism in relation to the extent of liver regeneration are expected after partial hepatectomy. There are few reports, however, about hepatic oxygen metabolism during liver regeneration. In this study, we evaluated changes in hepatic oxygen metabolism related to the regeneration rate, and the relationship between hepatic venous oxygen saturation (Shvo2) and liver regeneration after partial hepatectomy. METHODS: The work was done using 50% hepatectomized rats with continuous infusion of octreotide for inhibition of liver regeneration or with saline as control. The hepatic hemodynamics, oxygen metabolism, and Shvo2 levels as well as the regenerating liver status were evaluated for 3 days after hepatectomy. RESULTS: Administration of octreotide resulted in a significant reduction of the regenerating liver weight on days 1 and 3 after hepatectomy compared with the control group. Significantly decreased DNA synthesis and proliferating cell nuclear antigen labeling index were also found on day 1. Meanwhile, hepatic oxygen consumption (HVO2) and oxygen extraction ratio were significantly decreased in the octreotide-treated group on day 1. In contrast, the Shvo2 levels in the octreotide-treated group were significantly higher than those in the control group, and were inversely correlated with the HVO2. CONCLUSION: The remnant liver demands an increased amount of oxygen in relation to the extent of regeneration, and changes in the Shvo2 are inversely correlated with the HVo2. Therefore, monitoring the Shvo2 could be useful for estimating liver regeneration after partial hepatectomy.     

Decrease in regeneration capacity of rat liver after external biliary drainage.

In order to discover the effect of external biliary drainage on liver regeneration, we have produced a model system carrying cannula in the common bile duct of rat liver and examined the regeneration capacity of liver after partial hepatectomy under various conditions. Previously we have shown that hepatic cells proliferate by obstructive jaundice alone without partial hepatectomy [Terasaki et al; Jpn J Cancer Res 1991;82:170-175]. In the present study, we showed that DNA polymerase-alpha was induced by partial hepatectomy of rats suffering from obstructive jaundice and the induced level was similar to that of the normal regenerating liver. The level of DNA polymerase-alpha activity corresponded well to the liver regeneration capacity estimated by mitotic index. Contrary to our expectation, external biliary drainage for obstructive jaundice markedly suppressed the regeneration capacity of the remaining liver which was estimated by DNA polymerase-alpha activity, mitotic index and [3H]thymidine incorporation. The suppression may be due to the external biliary drainage itself because the liver regeneration of normal rats without jaundice was also suppressed by the biliary drainage. These results suggest that the external biliary drainage seriously suppresses the regeneration capacity of liver at least at the early stage of obstructive jaundice.     

Use of radiolabelled iododeoxyuridine as adjuvant treatment for experimental tumours of the liver

BACKGROUND: The aim of the study was to determine whether hepatic regeneration stimulates growth of tumour residing within the liver, and whether a difference in the rate of DNA synthesis in liver and tumour may be used to target cancer using the radiolabelled thymidine analogue 5-iodo-2'-deoxyuridine (IUdR). METHODS: Partial hepatectomy was performed on Buffalo rats bearing solitary nodules of syngeneic Morris hepatoma. Liver and tumour DNA synthesis was measured by incorporation of radioactive IUdR. [(125)I]IUdR was tested as an adjuvant therapy after hepatectomy in Buffalo rats bearing diffuse microscopic Morris hepatomas to simulate the clinical situation. RESULTS: Liver regeneration enhanced liver and tumour DNA synthesis as measured by incorporation of radioactive IUdR. Liver DNA synthesis returned to baseline by 7 days, whereas tumour DNA synthesis remained above baseline level. Hepatectomy enhanced the growth of microscopic liver tumours. [(125)I]IUdR (250 micro Ci or 1 mCi/kg) administered 4 days after hepatectomy significantly reduced tumour growth without signs of systemic toxicity or liver dysfunction. CONCLUSION: The local environment of the regenerating liver stimulates tumour growth. The thymidine analogue [(125)I]IUdR may be used preferentially to target tumour DNA synthesis in the regenerating liver, and may prove useful as an adjuvant therapy for hepatic tumours after surgical resection.     

Lipid metabolism in partially hepatectomized dogs and effect of hepatic periarterial neurectomy

Lipid metabolism in partially hepatectomized dogs was studied, by observing changes in serum lipids after hepatectomy and biosynthesis of lipids in the slices of the regenerating liver tissue. In addition, the effect of hepatic periarterial neurectomy was evaluated. Serum lipids decreased after partial hepatectomy and did not return to the preoperative level until the first postoperative week, whereas biosynthesis of lipids in the slices of the regenerating liver tissue was considerably augmented in the early postoperative period. This augmentation of lipid synthesis appears to be requirement for regeneration of the liver. When hepatic periarterial neurectomy plus partial hepatectomy was carried out, each lipid and lipoprotein fraction, except for FFA, showed a tendency to recover earlier from the immediate postoperative decrease and did not not show a late postoperative excessive increase. The decrease of α-lipoprotein in the immediate postoperative period was augmented and the time of the peak of concentration of pre-β-lipoprotein was hastened. Therefore, hepatic periarterial neurectomy seems to act in such a manner so as to maintain the homeostasis in lipid metabolism after partial hepatectomy and to activate the regenerative property of the residual liver in the early postoperative period.     

Plasminogen mediates liver regeneration and angiogenesis after experimental partial hepatectomy

BACKGROUND: Plasmin system components are upregulated after partial hepatectomy, but their contribution to surgery-induced hepatic angiogenesis and regeneration is unclear. Liver regeneration and angiogenesis after partial hepatectomy were examined in mice lacking plasminogen or urokinase plasminogen activator (uPA). METHODS: Mice with a single-gene deletion of plasminogen or uPA were subjected to 70 per cent partial hepatectomy. Liver regeneration was measured as relative liver weight and cell proliferation index. Angiogenesis was quantified by determining hepatic microvessel density after staining for sinusoidal endothelial cells. RESULTS: The liver remnant weight was significantly reduced in mice lacking plasminogen or uPA compared with that in wild-type mice on days 2 and 7 after partial hepatectomy. This correlated with impaired cell proliferation. In wild-type mice, regeneration was accompanied by a significant increase in microvessel density after hepatectomy; this increase was impaired in plasminogen-deficient mice. CONCLUSION: Plasminogen and uPA are essential for optimal liver regeneration. In addition, plasminogen appears to be a major determinant in regeneration-associated hepatic angiogenesis.     

Splenectomy improves survival by increasing arterial blood supply in a rat model of reduced‐size liver

Prevention of acute portal hyperperfusion in small‐for‐size livers by inflow modulation results in beneficial postoperative outcome. The objective of this study was to unravel the underlying mechanism, emphasizing the intimate relationship between portal venous (PV) and hepatic arterial (HA) blood flow (BF). Rats underwent partial hepatectomy (pHx), splenectomy before pHx or splenectomy and ligation of the A. hepatica before pHx. Portal venous blood flow (PVBF), hepatic arterial blood flow (HABF), and tissue pO₂ were assessed during stepwise resection from 30% to 90%. Hepatic regeneration and hypoxia‐responsive gene expression were analyzed in each group after nonlethal 85% pHx. 90% pHx caused a fourfold rise in PVBF, a slight decrease in HABF with a 50% reduction in pO₂, and high mortality. Splenectomy before pHx reduced the PVBF and caused a rise in HABF with doubling in tissue pO₂. An attenuation of hypoxia‐responsive gene expression turned into enhanced hepatocellular regeneration and improved survival. A. hepatica ligation abolished the beneficial effect of splenectomy on tissue oxygenation, proliferation, and outcome. In conclusion, the beneficial effect of splenectomy in small‐for‐size livers can be attributed to a rise in HABF with sufficient oxygen supply rather than to a reduced portal venous hyperperfusion to the remnant liver.     

The effects of protein and amino acids on DNA synthesis in regenerating liver

In order to estimate the effects of protein and amino acids on regenerating liver, the induction of enzymes involved in synthesis of DNA was studied in rats fed protein free diet. In the regenerating livers of rats of the protein free diet, increase of liver weight and DNA content were stopped 48 hours after hepatectomy, and induction of DNA synthesizing enzymes such as dCMP deaminase, ribonucleotide reductase, and thymidine kinase were depressed and shortened. On the other hand, induction of protein or RNA synthesizing enzymes such as polyamine, ornithine decarboxylase, and tyrosine aminotransferase were not depressed by protein deprivation. The results indicate that protein deprivation inhibits the DNA synthesizing enzymes specifically, and regenerating liver cells can not enter S phase of cell cycle. When rats were maintained solely by total parenteral nutrition after hepatectomy, amino acids were essential for induction of DNA synthesizing enzymes. In particular, induction of these enzymes were regulated by 7 amino acids include Val, Leu, Ile, Met, Trp, Phe, and Thr, and most of these plasma amino acid levels were depressed after hepatectomy. By administration of amino acids for 12 hours just after hepatectomy, the DNA synthesizing enzymes were almost normally induced. This suggests that amino acids administration just after hepatectomy is effective to induce the DNA synthesizing enzymes for hepatic regeneration.     

Cholestasis induces murine hepatocyte apoptosis and DNA synthesis with preservation of the immediate-early gene response

BACKGROUND: Major hepatic resection in patients with unrelieved obstructive jaundice carries an increased risk of postoperative liver failure. We hypothesized that cholestasis induces hepatocyte apoptosis and impairs hepatic regeneration by inhibiting up-regulation of the known immediate-early response genes, nuclear factor kappa B (NF-kappaB) and activating protein-1 (AP-1). The aim of this study was to determine whether the immediate-early gene response in hepatic regeneration remains intact in extrahepatic cholestasis. METHODS: Eight-week-old BALB/c mice underwent either sham operation (SO) or common bile duct ligation (BDL). Two-thirds partial hepatectomy (PH) was performed at 4 and 7 days, with remnant liver harvested 0, 15, 30, or 60 minutes after PH. Serum analysis for markers of cholestasis and histopathology was obtained. Proliferating cell nuclear antigen and terminal deoxyuridine triphosphate nick end labeling (TUNEL) immunohistochemistry for detection of DNA synthesis and apoptosis, respectively, was performed 4, 7, or 10 days after SO or BDL. Liver samples from 0, 15, 30, or 60 minutes after PH were analyzed for NF-kappaB and AP-1 DNA binding activity by using electrophoretic mobility shift assays. RESULTS: Increased serum bilirubin level and hematoxylin-eosin-stained liver sections confirmed cholestasis in BDL mice. BDL induced marked DNA synthesis and hepatocyte apoptosis in prehepatectomy liver at both 4 and 7 days. Substantially higher basal levels of both NF-kappaB and AP-1 binding activity were present in BDL compared with SO mice. Fold induction of NF-kappaB and AP-1, however, was similar between BDL and SO mice. Cholestasis induced hepatocyte DNA synthesis and apoptosis. Basal NF-kappaB and AP-1 DNA binding activity was increased in BDL mice, but fold induction of these immediate-early genes did not differ from controls. CONCLUSIONS: Although basal NF-kappaB and AP-1 DNA binding is increased in cholestasis, the immediate-early gene response to PH remains intact in BDL mice.     

Effects of preoperative transcatheter arterial embolization (TAE) on the liver following partial hepatectomy in rats

The safety of pre-operative transcatheter arterial embolization (TAE), especially on the relation to hepatic regeneration following partial hepatectomy, was evaluated in rats. TAE was done through a catheter cannulated into hepatic artery under laparotomy. The remarkable elevation of S-GOT and S-GPT levels were demonstrated a day after TAE, which returned to normal on third post operative day. No influence of the difference of embolized materials was seen on the changes of transaminase levels. TAE severely decreased hepatic microsomal functional mass measured by [14C]-aminopyrine breath test (ABT) and the recovery of microsomal functional mass was shown on the 14th day after TAE. Histologically, recanalization could not be revealed in embolized arterioles even on the 21st day after TAE. But trabecular pattern of hepatic lobules was preserved after TAE. The serious inhibition of DNA synthesis of regenerating liver was demonstrated when TAE was performed within 14 days prior to partial hepatectomy (p less than 0.001-0.05). The period from TAE to partial hepatectomy had a influence on the survival rate after partial hepatectomy, and when appropriate interval was taken after TAE, the survival rate increased significantly (33%-50% in 24 hours interval and 88% in 14 days interval). In conclusion, preoperative TAE remarkably suppressed hepatic regeneration after partial hepatectomy, and appropriate time when suppressed hepatic functional mass, such as microsomal functional mass measured by ABT, returned to pre TAE value was required to perform hepatectomy in safety.     

Morphological and functional changes after portal vein occlusion in rats

We investigated morphological and functional changes after portal vein occlusion in rats. Portal branches for the median and left lateral lobes were ligated, after which the lobes were examined micromorphologically. After embolization of the same branches, regenerative capacity was evaluated in normal livers and in livers with CCl₄-induced cirrhosis. Indocyanine green elimination, antithrombin III activity, and Kupffer cell density were also investigated. In another set of rats, the embolized lobes were resected 0, 2, 4, or 7 days after portal vein embolization (PVE), and endotoxin was injected intravenously 48h after each hepatectomy. In the ligated lobes, apoptotic hepatocytes were detected mainly around a widespread necrotic area on day 2, and among normal hepatocytes on day 7. In the nonembolized livers of control rats, increases were noted in liver weight, ornithine decarboxylase (ODC) activity, DNA synthesis, and mitosis of hepatocytes. In the cirrhotic livers, ODC activity was stimulated in a fashion similar to that seen in control liver, but DNA synthesis and weight change was delayed, although not significantly. On days 2, 4, 7, and 14 PVE, Kupffer cell density was about twice that seen in rats before PVE. Endotoxin-induced liver injury was slight if the rats had received PVE 4-7 days before the hepatectomy.     

Investigation of lipid peroxidation in regenerating rat liver]

The purpose of this study was to estimate the effects of lipid peroxidation in regenerating rat liver. Partial 70% hepatectomy was performed in rat according to Higgings and Anderson. EPC (alpha Toc: Ascorbic acid = 6:4, radical scavenger) was injected intravenously (5mg/kg weight) one hour before operation. Lipid peroxidation in regenerating liver reached a peak at 24 hours after operation. The administration of EPC markedly suppressed the increase of lipid peroxide in the plasma and remnant liver and that of GPT after hepatectomy, with subsequent good liver regeneration ratio. Moreover, the pretreatment with EPC remarkably elevated the activity of thymidine kinase (index of DAN synthesis). The EPC administration had not notable effects on the level of plasma ketone body ratio in animal but pathologically caused early advent of glycogen granule in the remnant liver tissue after partial hepatectomy, which reflected restoration of mitochondrial energy level. The results of the present study suggest that scavenger may be useful not only for impairment of liver dysfunction but also for recovery of mitochondrial energy level and DNA synthesis after liver resection.