Expression of messenger RNA for liver functions following 70% and 90% hepatectomy

Perturbations of urea cycle enzymes during posthepatectomy rat liver failure

Posthepatectomy liver failure (PHLF) may occur after extended partial hepatectomy (PH). If malignancy is widespread in the liver, the size of PH and hence the size of the future liver remnant (FLR) may limit curability. We aimed to characterize differences in protein expression between different sizes of FLRs and identify proteins specific to the regenerative process of minimal-size FLR (MSFLR), with special focus on postoperative day (POD) 1 when PHLF is present. A total of 104 male Wistar rats were subjected to 30, 70, or 90% PH (MSFLR in rats), sham operation, or no operation. Blood and liver tissue were harvested at POD1, 3, and 5 (n = 8 per group). Protein expression was assessed by proteomic profiling by unsupervised two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) liquid chromatography tandem mass spectrometry (LC-MS/MS), followed by supervised selected reaction monitoring (SRM)-MS/MS. In all, 1,035 protein spots were detected, 54 of which were significantly differentially expressed between groups and identifiable. During PHLF after PH(90%) at POD1, urea cycle and related proteins showed significant perturbations, including the urea cycle flux-regulating enzyme of carbamoyl phosphate synthase-1, ornithine transcarbamylase, and arginase-1, as well as the ornithine aminotransferase and propionyl-CoA carboxylase alpha chain. Plasma-ammonia increased significantly at POD1 after PH(90%), followed by a prompt decrease. At the protein level, we found perturbations of urea cycle and related enzymes in the MSFLR during PHLF. Our results suggest that these perturbations may augment urea cycle function, which may be pivotal for increased ammonia elimination after extensive PHs and potential PHLF.NEW & NOTEWORTHY Posthepatectomy liver failure (PHLF) is associated with high mortality. In a rat model of 90% hepatectomy, PHLF is present. Our results on liver tissue proteomics suggest that the ability of the liver remnant to sufficiently eliminate ammonia may be brought about by perturbation related to urea cycle proteins and that enhancing the urea cycle capacity may play a key role in surviving PHLF.

Metabolism for cyclosporin A during liver regeneration after partial hepatectomy in rats

AIM: To elucidate the metabolism and the effect of the cyclosporin A (CyA) as a representative immunosuppressive drug used in transplantation in a partially hepatectomized rat model.

METHODS: CyA was administered to rats that underwent a 70% hepatectomy. These rats were randomly assigned into three groups according to the dose of CyA administration as follows; (group 1) water, (group 2) 5 mg/kg CyA, (group 3) 10 mg/kg CyA. On postoperative days-1, 3, 7 and 14, the rats were killed to analyze the serum concentration of CyA, the liver regeneration ratio, biochemical or histological markers, and mRNA expression using reverse transcriptase-polymerase chain reaction method to determine albumin and cytochrome p450 expression.

RESULTS: The serum concentration of CyA in group 3 was significantly higher than group 2 during liver regeneration. CyA enhanced the liver regeneration in a dose dependent manner. The mRNA expression associated with CyA metabolism was significantly decreased on day 14, while preserving the albumin producing activity.

CONCLUSION: These data indicate that the p-450 activity required to metabolize the CyA may be reduced during regeneration of the remnant liver after a hepatectomy, which may, therefore, be linked to difficulty in controlling the optimal dose of CyA during early period of LDLT.

Synthesis of acute phase proteins in rats with cirrhosis exposed to lipopolysaccharide

BACKGROUND

In patients with cirrhosis, infection is frequent and a leading cause of death. This is secondary to various immunologic abnormalities in both the innate and the adaptive immune system. However, it remains unclear whether cirrhosis affects the inflammatory systemic component of the innate immunity, 'the acute phase response', mostly effectuated by the liver itself. We hypothesized that rats with cirrhosis raise a reduced acute phase response induced by lipopolysaccharide (LPS).

RESULTS

We examined the acute phase response induced by intraperitoneal injection of a low dose of LPS, in sham operated control animals and in rats with liver cirrhosis induced by bile duct ligation (BDL). We measured the serum concentrations of the most important acute phase proteins and their liver tissue gene expressions, assessed by mRNA levels. The BDL-model itself increased the serum concentration of alpha1-acid glycoprotein (alpha1AGP) and haptoglobin. LPS was lethal to 25% of the cirrhotic animals and to none of the controls. Twenty-four hours after LPS, the serum concentration of alpha1AGP and haptoglobin, the mRNA level of these acute phase proteins and of alpha2-macroglobulin and thiostatin rose to the same level in the animals with cirrhosis and in controls.

CONCLUSION

In rats with experimental cirrhosis LPS caused high mortality. In the survivors, the cirrhotic liver still synthesized acute phase proteins as the normal liver, indicating a normal hepatic contribution to this part of the acute phase response.

Regulation of hepatic insulin-like growth factor-binding protein-1 gene expression by insulin: central role for mammalian target of rapamycin independent of forkhead box O proteins

The expression of IGF-binding protein-1 (IGFBP-1) is induced in rat liver by dexamethasone and glucagon and is completely inhibited by 100 nM insulin. Various studies have implicated phosphatidylinositol 3-kinase, protein kinase B (Akt), phosphorylation of the transcription factors forkhead in rhabdomyosarcoma 1 (Foxo1)/Foxo3, and the mammalian target of rapamycin (mTOR) in insulin's effect. In this study we examined insulin regulation of IGFBP-1 in both subconfluent and confluent hepatocytes. In subconfluent hepatocytes, insulin inhibition of IGFBP-1 mRNA levels was blocked by inhibiting PI3 kinase activation, and there was a corresponding inhibition of Foxo1/Foxo3 phosphorylation. In these same cells, inhibition of the insulin effect by rapamycin occurred in the presence of insulin-induced Foxo1/Foxo3 phosphorylation. In confluent hepatocytes, insulin could not activate the phosphatidylinositol 3-kinase (PI3 kinase)-Akt-Foxo1/Foxo3 pathway, but still inhibited IGFBP-1 gene expression in an mTOR-dependent manner. In subconfluent hepatocytes, the serine/threonine phosphatase inhibitor okadaic acid (100 nM) partially inhibited IGFBP-1 gene expression by 40%, but did not produce phosphorylation of either Akt or Foxo proteins. In contrast, 1 nm insulin inhibited the IGFBP-1 mRNA level by 40% and correspondingly activated Akt and Foxo1/Foxo3 phosphorylation to a level comparable to that observed with 100 nM insulin. These results suggest a potential role for a serine/threonine phosphatase(s) in the regulation of IGFBP-1 gene transcription, which is not downstream of mTOR and is independent of Akt. In conclusion, we have found that in rat liver, insulin inhibition of IGFBP-1 mRNA levels can occur in the absence of the phosphorylation of Foxo1/Foxo3, whereas activation of the mTOR pathway is both necessary and sufficient.

The relationship between albumin, other plasma proteins and variables, and age in the acute phase response after liver resection in man

A large series of plasma albumin (ALB, g/dl) and simultaneous blood and clinical measurements were prospectively performed on 92 liver resection patients, and processed to assess the correlations between ALB, other plasma proteins, additional variables and clinical events. The measurements were performed preoperatively and at postoperative day 1, 3 and 7 in all patients, and subsequently only in those who developed complications or died. In patients who recovered normally ALB was 4.3 +/- 0.4 g/dl (mean +/- SD) preoperatively, 3.7 +/- 0.7 at day 1 and 3, and 3.9 +/- 0.4 at day 7. In patients with complications its decrease was more prolonged. In non-survivors it was 3.4 +/- 0.4 preoperatively, 3.0 +/- 0.4 at day 1, and then decreased further. Regression analysis showed direct correlations between ALB and pseudo-cholinesterase (CHE, U/l, nv 5300-13000), cholesterol (CHOL, mg/dl), iron binding capacity (IBC, mg/dl), prothrombin activity (PA, % of standard reference) and fibrinogen, an inverse correlation with blood urea nitrogen (BUN, mg/dl) for any given creatinine level (CREAT, mg/dl), and weaker direct correlations with hematocrit, other variables and dose of exogenous albumin. An inverse relationship found between ALB and age (AGE, years) became postoperatively (POSTOP) also a function of outcome, showing larger age-related decreases in ALB associated with complications (COMPL: sepsis, liver insufficiency) or death (DEATH). Main overall correlations: CHE = 287.4(2.014)(ALB), r = 0.73; CHOL = 16.5(1.610)(ALB) (1.001)(ALKPH), r = 0.71; IBC = 68.6(1.391)(ALB), r = 0.64; PA = 13.8 + 16.0(ALB), r = 0.51; BUN = 21.3 + 20.2(CREAT) - 6.2(ALB), r = 0.91; ALB = 5.0-0.013(AGE) - {0.5 + 0.003(AGE)( COMPL ) + 0.012(AGE)( DEATH )}( POSTOP ), r = 0.74 [p < 0.001 for each regression and each coefficient; ALKPH = alkaline phosphatase, U/l, nv 98-279, independent determinant of CHOL; discontinuous variables in italics label the change in regression slope or intercept associated with the corresponding condition]. These results suggest that altered albumin synthesis (or altered synthesis unable to compensate for albumin loss, catabolism or redistribution) is an important determinant of hypoalbuminemia after hepatectomy. The correlations with age and postoperative outcome support the concept that hypoalbuminemia is a marker of pathophysiologic frailty associated with increasing age, and amplified by the challenges of postoperative illness.

Effect of lipopolysaccharide on in vivo and genetic regulation of rat urea synthesis

BACKGROUND

The acute phase response causes a negative nitrogen balance. It is unknown whether this involves regulation of hepatic urea synthesis.

METHODS

We examined the in vivo capacity of urea nitrogen synthesis (CUNS), mRNA levels of urea cycle enzyme genes and galactose elimination capacity (GEC) during moderate and severe acute phase response induced by low- and high-dose lipopolysaccharide (LPS) in rats.

RESULTS

Low-dose LPS doubled CUNS (P<0.05), decreased the mRNA level of the rate-limiting urea cycle enzyme (arginino succinate synthetase (ASS) by 26% (P<0.05) and did not change GEC. High-dose LPS did not change CUNS, decreased the mRNA level of the flux-generating enzyme carbamoyl phosphate synthetase (CPS) by 11% (P<0.05) and the rate-limiting urea cycle enzyme (ASS) by 27% (P<0.05) and almost halved GEC (P<0.05).

CONCLUSION

The moderate acute phase response up-regulated in vivo urea synthesis but had the opposite effect on gene level. The severe acute phase response decreased the functional liver mass that attenuated the increase in urea synthesis.

Modulation of plasma fibrinogen levels in acute-phase response after hepatectomy

In acute-phase response, the use of amino acids is redirected to supporting the synthesis of proteins for host defence and tissue repair. Fibrinogen is one of these proteins, and its plasma levels commonly increase in acute-phase conditions. After hepatectomy, this pattern may be modified by the variable impact of postoperative liver dysfunction. Our study was performed to specifically assess and quantify this aspect. Data were collected prospectively on 82 hepatectomized patients; 62 recovered normally, 20 had major complications (most commonly sepsis). Plasma fibrinogen and a large series of complementary variables were determined preoperatively and at postoperative days 1, 3 and 7 in all patients and until recovery, or death in those with complications. Multiple regression analysis showed that postoperative changes in fibrinogen (deltaFIB, micromol/l) were simultaneously related to the number of resected liver segments (NSEG), total bilirubin (BIL, micromol/l), aspartate aminotransferase (AST, U/l, n.v. 5-45), albumin (ALB, g/l), prothrombin activity (PA, % of standard reference), age (AGE, years) and basal preoperative fibrinogen (PFIB, micromol/l): deltaFIB = -0.51(NSEG) - 0.71(Log(n)BIL) - 0.74(Log(n)AST) + 0.11(ALB) + 0.09(PA) - 0.06(AGE) - 0.55(PFIB) + 7.74 (n=362, r2=0.68, p<0.001). In addition, an early postoperative tendency for low fibrinogen was associated with the subsequent development of complications or death. Our study quantifies the impact of size of hepatectomy and dysfunction of residual liver in modulating postoperative fibrinogen level and suggests that failure of fibrinogen to increase may signal an unfavorable condition limiting up-regulation of acute-phase response and increasing liability to complications.

KUPFFER CELL???DEPLETED RATS HAVE A DIMINISHED ACUTE-PHASE RESPONSE FOLLOWING MAJOR LIVER RESECTION

Partial hepatectomy (PH)-induced Kupffer cell (KC) activation results in a rapid release of cytokines inducing the acute-phase response (APR). This study was done to evaluate the role of Kupffer cells (KCs) in the course of the APR following PH and a consecutive endotoxin challenge. KC depletion was performed in rats by i.v. administration of 1 mL liposome-encapsulated dichloromethylene diphosohonate (Cl2MDP). Control rats received 1 mL NaCl 0.9%. Forty-eight hours later, PH was performed. At 24 h after PH, rats were randomized to receive either 1 mL NaCl 0.9% (saline) or 50 microg/kg LPS i.v. in 1 mL. Animals were sacrificed at 4 h after LPS or saline infusion. The APR was determined by measuring hepatic gene expression of alpha 2-macroglobulin, alpha 1-acid glycoprotein, and IL-6 and expression of hepatic albumin. The APR was significantly depressed in KC-depleted rats. Despite increased IL-6 mRNA synthesis in response to low-dose LPS, no enhancement of acute-phase protein synthesis (APP) was found in KC-depleted rats. Hepatic failure was most profound in KC-depleted rats, as indicated by elevated plasma levels of liver transaminases and ammonia. We conclude that after PH, KC function in the remnant liver is important for the acute-phase reaction and reduces endotoxin-induced hepatocyte damage.

Gene expression profiles of livers from thermally injured rats

The liver plays an important role in a severe thermal injury by modulating immune function, inflammatory processes and the acute phase response, which are an orchestrated attempt to restore homeostasis. Using high-density oligonucleotide arrays, we examined the gene expression profile in the livers of rats between 2 and 240 h after a 40% total body surface area (TBSA) burn. Alterations in gene expression unique to a thermal injury were identified. Approximately 39 genes out of 8700 genes on each array across all the time points showed a significant change in expression patterns. Real time reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses verified significant changes in early growth response-1 (Egr-1) messenger RNA (mRNA) and protein levels corresponding to the array data. Significant increases in serum levels of alpha-2-macroglobulin that correspond to changes in its mRNA levels were observed at 6 and 24 h after burn, p<0.05. The genomic pattern for liver in the hypermetabolic phase after the burn injury involves transcription factors, stress and inflammatory responses, cytoskeletal and extracellular matrix modifications, and regulation of cell proliferation and differentiation. During the initial phase of thermal injury gene expression profiles in the liver may provide some insight into how cellular protection mechanisms and systemic hypermetabolism are initiated and controlled. The genome wide changes observed may provide a rational therapeutic strategy to improve burn care.

Review article: adult-to-adult right hepatic lobe living donor liver transplantation

Spurred on by the critical shortage of cadaveric livers, adult-to-adult right hepatic lobe living donor liver transplantation has grown rapidly as a therapeutic option for selected patients. In the USA alone, the number of living donor liver transplantations has increased six-fold in the last 4 years. The therapy can be complex, bringing together a variety of disciplines, including transplantation medicine and surgery, hepatology, psychiatry and medical ethics. Moreover, living donor liver transplantation is still defining itself in the adult-to-adult application. Uniform standards, guidelines and long-term outcomes are yet to be determined. Nevertheless, initial success has been remarkable, and a basic understanding of this field is essential to any physician contemplating options for their liver failure patients. This review covers a range of topics, including recipient and donor selection and outcomes, donor risk, controversies and future issues.

Living donor liver transplant recipients achieve relatively higher immunosuppressant blood levels than cadaveric recipients

Two recent brief reports suggest that recipients of living donor liver transplants achieve higher levels of immunosuppressive agents than cadaveric (CAD) liver transplant recipients administered the same dose. These results could have important implications regarding the dosing of immunosuppressives in living donor liver transplant recipients. We report our findings relative to immunosuppressive doses and levels in a cohort of 46 living donor liver transplant recipients. Immunosuppressive blood levels and doses were recorded weeks 1, 2, 3, and 4 and months 2, 3, 4, 5, and 6 for 46 living donor liver transplant recipients and 66 matched CAD liver transplant recipients who underwent transplantation between August 1997 and May 2001. The ratio of level to dose also was recorded at each interval. The mean overall cyclosporine A dose was similar in living donor liver transplant recipients (323 mg/d) compared with CAD recipients (344 mg/d; P = not significant [NS]). The mean overall tacrolimus dose was 15% lower in patients who underwent living donor liver transplantation (LDLT; 5.7 mg/d) than CAD transplantation (6.7 mg/d), although statistical significance was not achieved (P =.08). The mean overall cyclosporine A level was 18% higher in those undergoing LDLT (275 ng/mL) than CAD transplantation (234 ng/mL; P =.015). The mean overall tacrolimus level was the same in living donor liver transplant recipients (10.8 ng/mL) and CAD recipients (10.2 ng/mL; P = NS). The overall cyclosporine A level-dose ratio was 26% higher for those undergoing LDLT (0.83) than CAD transplantation (0.66; P =.01). The overall tacrolimus level-dose ratio was 26% higher for those undergoing LDLT (1.82) than CAD transplantation (1.44; P =.01). In conclusion, (1) living donor liver transplant recipients achieve higher blood levels of tacrolimus and cyclosporine A for a given dose compared with CAD recipients, and (2) this difference is observed up to 6 months after transplantation, when hepatic regeneration is completed.

Kinetics and mechanisms of hepatic acute phase response to subtotal partial hepatectomy and cultural impact on environmental hepatic end-stage liver injury in the homeless

Intoxication and liver damage induced by carbon tetrachloride (CCl(4)), aflatoxin B1, diabetes, and subtotal partial hepatectomy (PH(90)) in rats in which approximately 90% of the total hepatic tissue mass is surgically removed produces an acute-phase response (APR) whose initial stage prior to regression closely mimics the APRs associated with the life-threatening hepatic failure seen in the homeless. Rats treated by PH(90)were either healthy, CCl(4)-intoxicated, diabetic, or alflatoxin B1 (AFB1) intoxicated to the point of 75% liver insufficiency. It is well documented that high rates of mortality following PH(90)in aseptic rats could be minimized by supplementing drinking water with 20% glucose, organic components of L-15 medium and housing animals in cages maintained at 33-35;C. Aseptic rats showed a mild 20-30% decrease in APR proteins during the first 4-5 days following PH(90), while a maximal APR was noted 9-12 days post PH(90)and lasted for ~30 days when it returned to values close to those of healthy controls. This delay in hepatic APR of the remnant caudate lobe favoured replacement of lost basophilic clumps and ribosomes. The newly synthesized ribosomes of the nascent hepatocytes quantitatively maintained the APR signals of the injured caudate hepatocytes, and biosynthesized and released a typical spectrum of APR proteins. We suggest that massively injured liver has decoded an already stored and irreversible DNA-biochemical sequence of events in which priority is given to recovery of lost tissues by delaying an APR response to injury. In PH(90)of diabetic and CCl(4)-intoxicated rats, the hepatic dual functions of regeneration and APR processes associated with intoxication-initiated catabolic signals, created a heavy metabolic burden on the remnant caudate lobe leading to higher rates of mortality. APR of healthy rats to AFB1 parallels that of alpha-amanitin-induced intoxication. Similarly, within shorter time scale proportional to the severity of surgery, livers undergoing 75% partially hepatectomy (PH(75)) delayed both the onset and regression of APR. We are therefore led to believe that approaches other than liver transplantation should be considered as viable alternatives in the treatment of various acute and chronic liver diseases to avoid rejection and retransplantation. Scarcity of cadaveric liver has forced the medical community to investigate xenotransplantation with its unknown risks. Concomitantly, it is suggested that in view of the incalculable risks of indifference, the homeless must receive much improved medical care as we have found that two-dimensional immunoelectrophoretic assay of their serum is indicative of acute and chronic liver injury. The scientific and moral interrelationships of related matters are illuminated.

Liver gene regulation in rats following both 70 or 90% hepatectomy and endotoxin treatment

BACKGROUND

The metabolic state effect of liver failure on liver gene regulation was evaluated in a rat model.

METHODS

Following 70 or 90% hepatectomy and lipopolysaccharide or vehicle treatment at intervals up to 24 h, the liver remnants were analyzed for mRNA levels for acute-phase, liver-specific and growth-related proteins.

RESULTS

After 70% hepatectomy mRNA for alpha 1-acid glycoprotein, alpha 2-macroglobulin, thiostatin and fibrinogen, haptoglobin increased three- to sevenfold (P < 0.05), and mRNA for cyclin D and histone 3 increased seven- and 15-fold (P < 0.05), respectively. After lipopolysaccharide injection and 70% hepatectomy were done, mRNA for acute-phase proteins raised significantly (P < 0.05), more to five to 20-fold, while mRNA for growth-related proteins raised significantly (P < 0.05) less to three- to fourfold. After 90% hepatectomy, acute-phase protein mRNA increased five- to ninefold (P < 0.05) more than after 70% hepatectomy, while mRNA for histone 3 and cyclin D did not increase within 24 h, which indicates a delayed growth after 90% hepatectomy. In 90% of hepatectomized rats treated with lipopolysaccharide, acute-phase protein mRNA raised three- to sixfold (P < 0.05) less than after vehicle treatment.

CONCLUSION

In endotoxemia from liver failure, the synthesis of acute-phase proteins is upregulated by gene regulation at the expense of that for regeneration, which may be an appropriate response for immediate survival. In severe liver failure, endotoxin may interfere with the appropriate gene regulation.

Differential suppression of liver-specific genes in regenerating rat liver induced by extended hepatectomy

BACKGROUND/AIMS

The function of the remnant liver is critical to survival of patients following an extended hepatectomy. The aim of this study was to determine whether proliferating hepatocytes in the remnant liver preserve the expression of liver-specific genes.

METHODS

Using regenerating rat livers after 30, 70, and 90% partial hepatectomy (PHx), Northern blot analyses were performed with probes for seven liver-specific genes, six growth-related genes, two housekeeping genes and two acute phase reactant protein genes.

RESULTS

During the regeneration after 90% PHx, the transcription of liver-specific genes showed three chronological patterns: transcription of serum albumin and cytochrome P450 2B decreased rapidly and reached a nadir at 6 to 24 h after PHx; those of apolipoprotein A-1, phosphoenolpyruvate carboxykinase and ornithine transcarbamylase decreased gradually until 24 to 48 h; those of UDP-glucuronosyltransferase and hepatocyte nuclear factor 4 did not show any changes until 48 h after PHx. In contrast, expression levels of all the growth-related genes and of housekeeping genes increased rapidly after PHx. After 30 and 70% PHx, expression of these genes changed in a similar manner to the 90% PHx case but to a lower extent.

CONCLUSIONS

Based upon the fractions of Ki-67 positive hepatocytes in remnant livers, we could estimate the degree of expression of each liver-specific gene in the proliferating hepatocytes. The serum albumin gene was completely suppressed, while that encoding UDP-glucuronosyltransferase was not affected. These results correlated well with the patterns of albumin and bilirubin in rat serum after PHx. Other liver-specific genes were moderately suppressed in proliferating hepatocytes. Thus, expression of liver-specific gene is differentially suppressed when hepatocytes enter a proliferation cycle. Those that are unaffected may be indispensable for maintaining the homeostasis of the living organism.

Growth factors and gene expression in cultured rat hepatocytes

BACKGROUND/AIM

The aim of this study was to evaluate the effect of replication on function variables in cultured hepatocytes.

METHODS

Isolated rat hepatocytes were cultured in HCM medium and plated on collagen-coated dishes at cell densities from 0.2 x 10(5) (subconfluent) to 1.0 x 10(5) x cm(-2) (confluent) with and without addition of hepatocyte growth factor, epidermal growth factor and insulin-like growth factor-I. The synthesis rate was measured for DNA, albumin, urea, and glucose together with mRNA levels (Northern blots) for albumin, urea cycle enzymes, and acute phase and "house-keeping" proteins.

RESULTS

In subconfluent culture the synthesis of DNA and urea was higher (118% and 112%, respectively), and of albumin and glucose lower (40% and 67%, respectively) than in confluent culture. The mRNA levels of carbamoylphosphate synthase, argininosuccinate synthetase, argininosuccinate lyase, arginase, a2-macroglobulin, beta-fibrinogen, and albumin were lower (23%, 58%, 77%, 33%, 12%, 50%, and 51%, respectively) in subconfluent culture compared with confluent culture. Relatively increased levels were found for beta-actin (109%) and alpha-tubulin (136%). In subconfluent culture hepatocyte growth factor increased the DNA synthesis rate 6-fold, epidermal growth factor 3-fold, and insulin-like growth factor-I 2-fold; that of albumin, urea and glucose was not increased significantly. In confluent culture the effect of growth factors on synthesis rates was not significant, and the growth factors had little influence on mRNA levels.

CONCLUSIONS

Hepatocytes produce urea at the same rate in subconfluent as in confluent culture in spite of a lower mRNA level of urea cycle enzymes. Hepatocyte growth factor and epidermal growth factor increase DNA synthesis markedly in subconfluent culture only, without significantly changing the ratio between subconfluent and confluent culture of other variables. This suggests that active replication is not an important cause of the relatively low liver-specific function of hepatocytes in subconfluent culture.

Vasopressin reverses mesenteric hyperemia and vasoconstrictor hyporesponsiveness in anesthetized portal hypertensive rats

We recently reported that vasopressin analogues correct the in vitro vascular hyporeactivity to adrenergic vasoconstrictors in portal hypertensive rats. The aim of the present study was to determine whether vasopressin reduces splanchnic blood flow in portal vein-ligated (PVL) rats by restoring vasoconstrictor responsiveness in vivo. The ultrasonic transit time-shift technique was used for blood flow measurements. At basal conditions, blood flow through the superior mesenteric artery was elevated 1.6-fold in PVL rats as compared with sham-operated (SHAM) control rats. PVL rats also exhibited blunted mesenteric constrictor responses to the adrenoceptor agonist, phenylephrine (0.03-1 micromol x min(-1) x kg(-1)). Terlipressin (2-20 microg x k(-1)) and arginine vasopressin (3-300 pmol x min(-1) x kg(-1)) dose-dependently reduced, and at the highest doses, even abolished, the difference in mesenteric blood flow (MBF) between PVL and SHAM rats. When expressed as percent changes relative to baseline, mesenteric arterial responses to terlipressin and arginine vasopressin were found to be enhanced in PVL rats as compared with SHAM rats. Moreover, pretreatment with terlipressin (20 microg x kg(-1)) reversed the mesenteric hyporesponsiveness to phenylephrine of PVL rats. These vasopressin effects were independent of the nitric oxide (NO) pathway, because they were not mimicked by inhibition of NO synthesis with N(G)-nitro-L-arginine methyl ester (L-NAME) (0.1-10 mg x kg(-1)). These data indicate that pharmacological doses of vasopressin reverse the splanchnic hyperemia by restoring the responsiveness to adrenergic vasoconstrictors in portal hypertensive rats.

Expression of liver-specific functions in rat hepatocytes following sublethal and lethal acetaminophen poisoning

AIM

In order to study the short-term effect of moderate and severe reduction of liver function by acetaminophen poisoning of different severity on gene expression for liver-specific functions, rats were given 3.75 and 7.5 g per kg body weight acetaminophen intragastrically. The lower dose is associated with low mortality; after the higher dose, most rats die at between 12 and 24 h.

METHODS

In the morning, 1 1/2, 3, 6, 9, and 12 h after the injection, the rats were killed and RNA was extracted from liver tissue. By slot-blot hybridization mRNA steady-state levels were determined for enzymes involved in metabolic liver functions, i.e. ureagenesis, gluconeogenesis, and drug metabolism, for acute phase proteins, "house-keeping" proteins, and for proteins related to liver regeneration. Results were expressed as per cent of the level in similarly fasted, untreated rats of the same stock

RESULTS

After the smaller dose of acetaminophen, most of the examined mRNA levels were increasing during the experimental period, being two- to four-fold elevated in relation to control after 6 to 12 h. Rats receiving the lethal dose either showed no or a later and smaller increase, and in several cases a fall towards the end of the experiment. The greatest differences were seen for mRNA of arginase, beta-fibrinogen, alpha 1-acid glycoprotein, alpha-tubulin, histone 3, TGF beta, and cyclin d, i.e. proteins associated with acute phase response and liver cell replication and maintenance.

CONCLUSIONS

It is concluded that reversible intoxication with acetaminophen induces an adaptive modulation of mRNA expression of liver functions and regeneration which is lacking after severe intoxication. This adaptation, with emphasis on acute phase response and regeneration, may be crucial for recovery after acetaminophen intoxication. If this also applies to the intoxication in man, estimates of the corresponding variables may be clues to the prognosis of acetaminophen-induced fulminant hepatic failure.