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The intact liver exists in a state of replicative quiescence. The factor(s) responsible for maintaining this state and their tissue sources have yet to be identified. Because the colon synthesizes and/or absorbs numerous agents that inhibit hepatocyte proliferation, the principle purpose of this study was to determine whether total colectomy would result in the conversion of quiescent livers to a state of replicative competence. Thus, adult, male Sprague-Dawley rats (250-300 g) were randomized to undergo either total colectomy with ileostomy or sham surgery. Thereafter, rats were sacrificed (N=3-6/group) at times 15 and 30 min and 1, 2, 6, and 24 hr and the livers analyzed by Northern blot analyses for mRNA of the following immediate-early proto-oncogenes (IEP genes): c-fos, c-jun, and c-myc. Rats sacrificed at 24 hr also had hepatic regenerative activity documented by [3H]thymidine incorporation into hepatic DNA. The results of the study revealed that within 15 min, c-fos and c-jun mRNA expression increased in colectomized rats, with peak expression occurring at 30 and 60 min, respectively. c-myc mRNA expression was more delayed, with peak expression occurring at 6 hr post-colectomy. IEP gene expression also increased somewhat in sham-colectomy controls but the increases were not as prompt and, in general, were of lower magnitude than those in the colectomy group. Despite the differences in IEP gene expression between the two groups, [3H]thymidine incorporation at 24 hr was similar (mean+/-SE: colectomy group, 17.2+/-2.6 dpm/microg DNA; sham-colectomy controls, 14.8+/-1.4 dpm/microg DNA). To determine whether the increases in IEP gene expression expedite or augment the hepatic regenerative response to partial hepatectomy (PHx), rats that had undergone colectomy or sham colectomy 1 hr earlier and rats with no previous abdominal surgery then underwent a 70% PHx and were sacrificed at 8, 16, and 24 hr thereafter. At each time interval, [3H]thymidine incorporation was documented and found to be similar in the three groups. In conclusion, the results of this study indicate that total colectomy, and to a lesser extent abdominal surgery, induces the conversion of an intact, quiescent liver to a state of replicative competence. The results also suggest that, in addition to colectomy, the presence of mitogens and/or co-mitogens is required for further progression of hepatocytes through the cell cycle. Finally, a "primed" liver does not respond more promptly or vigorously to a regenerative stimulus than a "resting" liver.

The capacity for the liver to regenerate after injury or resection has long been recognized, as implied by the legend of Prometheus. Resections of up to 70% of the liver are followed by a sequence of events that generally result in complete restitution of hepatic mass and function. Hypertrophy of hepatocytes begins within hours, with accumulation of amino acids and triglycerides and activation of enzymes that are associated with proliferative activity. Increased DNA synthesis is associated initially with hyperplasia of hepatocytes, and then other cells, which begins in the periportal region and spreads in a wave-like fashion to the pericentral region of the lobule. Quiescent hepatocytes are primed to enter the cell cycle and then proceed through the G1/S and G2/M restriction points, under the influence of a variety of proteins, growth factors (especially hepatocyte growth factor) and cycle dependent kinases. At each stage there is interplay between growth promoters and inhibitors, including transforming growth factor-beta and GABA. Factors that initiate hepatic regeneration are unknown, and might include hepatic depolarization, increases in blood flow, destruction of liver matrix (with release of growth factors), and increased production or expression of growth promoters compared to inhibitors. Regenerative activity increases with the amount of resection to a point, and then relatively declines. Uncontrolled proliferation of liver tissue after resection or injury is not necessarily beneficial, because it could lead to a diversion of resources from the maintenance of hepatic function and to an increased risk of neoplasia. Therefore, it is unclear whether clinicians should attempt to enhance hepatocyte regeneration. Since both hepatic regeneration and metabolic function require energy from high-energy nucleotide triphosphates, especially adenosine triphosphate (ATP), a reasonable strategy might be to augment energy delivery and ATP production. Mortality rates after limited (fewer than 70%) resections and mild or moderate injuries of previously normal livers are low, and supportive care is often sufficient. The prognosis is unclear; however, in cases of more massive resection, resections in the setting of underlying liver disease or cirrhosis, and fulminant hepatic failure, and liver transplantation is still an important option.

The trigger of the liver regeneration cascade is currently unknown and has been the subject of debate. We hypothesize that, following 2/3 partial hepatectomy (PHX), an increase in the blood flow-to-liver mass ratio results in shear stress-induced nitric oxide (NO) release, which triggers the liver regeneration cascade. Portal venous pressure (PVP), reflecting shear stress in the liver, increased to the same extent following PHX and selective portal vein branch ligation (PVL), a hemodynamic model of PHX, suggesting similar amounts of shear stress in both models. Two indices of the initiation of the liver regeneration cascade were used: proliferative factor (PF) activity in blood 4 h after PHX or PVL and hepatic c-fos mRNA expression 15 min. after PHX or PVL. PF activity and c-fos mRNA expression were increased to similar extents after PHX and PVL, suggesting a similar stimulus in both models. PF activity and c-fos mRNA expression were inhibited by administration of the nitric oxide synthase antagonist, l-NAME, and the NO donor, SIN-1, reversed the inhibition in both models. These results provide support for the hypothesis that a hemodynamic change results in increased shear stress in the liver causing generation of NO, which then triggers the liver regeneration cascade., (Copyright 2001 Academic Press.)

Background & Aims: The effects of "social drinking" on the liver have yet to be fully documented. The aim of this study was to document the effects of daily light, moderate, and heavy ethanol exposure on hepatic regenerative activity in the rat., Methods: Adult male Sprague-Dawley rats underwent daily gavages with 1.0 (light), 2. 0 (moderate), or 4.0 (heavy) g/kg of ethanol or tap water (controls) for 30 days before 70% partial hepatectomy (PHx). Hepatic regenerative activity was then documented on days 1, 3, 5, and 7 after PHx., Results: Compared with controls, restitution of liver mass, [(3)H]thymidine incorporation, and proliferating cell nuclear antigen expression were decreased in the heavy (-10%, -60%, and -36%, respectively), unchanged in the moderate (-4%, -8%, and -16%, respectively), and increased in the light (+6%, +38%, and +29%, respectively) ethanol groups. Messenger RNA differential display of resected livers at PHx identified a band present only in the light ethanol group that encodes a unique 47-kilodalton protein with growth-promoting features designated light ethanol-induced stimulatory protein., Conclusions: The results indicate that light ethanol consumption enhances hepatic regenerative activity after PHx in rats. Further studies are required to determine the mechanism involved and whether social drinking has beneficial or adverse effects on the natural history of acute or chronic liver disease in humans.

The purpose of this study was to identify the mechanism(s) whereby acute ethanol exposure inhibits hepatic regenerative activity in the rat. Adult, male, Sprague-Dawley rats (200-250 g) were randomized to receive either ethanol (1 g/kg i.p. q 4 h) or an equal volume of saline (controls) for 24 h beginning 1 h prior to a 70% partial hepatectomy (PHx). At 0, 3, 6, 12 and 24 h post-PHx, rats were sacrificed (N = 4-6/group), and the expression of the following genes associated with inhibition of hepatocyte proliferation were documented; p53, p21, transforming growth factor-beta1 (TGF-beta1) and gamma aminobutyric acid transport protein (GABA-TP). Inhibition of hepatic regenerative activity was confirmed by 3H-thymidine incorporation into hepatic DNA at 24 h post-PHx. The results of the study revealed that in ethanol-treated rats, DNA synthesis was inhibited by 37% when compared to saline-treated controls (p < 0.01). Regarding suppressor gene expression, both p21 and TGF-beta1 mRNA expression in ethanol-treated rats were similar to those obtained in saline-treated controls. Although p53 mRNA expression differed in the two groups, in the ethanol-treated group, p53 mRNA expression was decreased rather than increased (relative to controls) at 24 h post-PHx, a finding not in keeping with inhibition of DNA synthesis. GABA-TP mRNA was strongly expressed prior to PHx in both ethanol- and saline-treated rats. Following PHx, GABA-TP mRNA expression decreased in both groups but remained low in the saline-treated group while returning to pre-PHx values in ethanol-treated rats. In summary, the results of this study indicate that the inhibitory effects of ethanol on hepatic regeneration are not associated with significant or the appropriate changes in mRNA expression of the p53, p21 or TGF-beta1 suppressor genes. On the other hand, transcriptional changes in GABA-TP gene expression post-PHx are in keeping with an inhibitory effect of GABA on hepatic regeneration.

Recently, it has been suggested that ethanol-induced inhibition of liver regeneration results from decreases in hepatic putrescine levels and/or increases in hepatic gamma-aminobutyric acid (GABA)ergic activity. Because putrescine can be metabolized by diamine (DAO) and monoamine (MAO) oxidases to GABA, we documented the effects of acute ethanol exposure on hepatic MAO or DAO activity following partial hepatectomy (PHx) in rats. We also documented the effects of ethanol on GABA transaminase (GABA-T), the enzyme responsible for GABA metabolism in the liver, and tissue putrescine and GABA levels. Adult, male Sprague-Dawley rats (200-250 g) were treated with either ethanol (3 g/kg) or equal volumes of saline by gastric gavage 1 h prior to a 70% PHx or sham surgery. Rats were then sacrificed (n = 5-7/group) at various times (0-72 h) post-PHx. Enzymatic activity and putrescine/GABA levels were determined by standard isotopic techniques and high-performance liquid chromatography respectively. Hepatic DAO activities in ethanol-treated rats were transiently higher than in saline-treated controls (30% increases at 6 h, p < 0.05). Hepatic MAO and GABA-T activities in acute ethanol-treated rats were essentially identical to saline-treated controls. Although hepatic putrescine levels were similar in ethanol- and saline-treated rats, hepatic GABA levels were approximately three times higher in ethanol-treated rats at 12 and 24 h post-PHx (p < 0.0001). In conclusion, the results of this study indicate that acute ethanol exposure has a limited effect on the enzymatic conversion of putrescine to GABA following partial hepatectomy in the liver. The results also indicate that increased GABAergic inhibition rather than decreased putrescine stimulation is more likely to play a role in ethanol-induced inhibition of hepatic regeneration.

Background/aims: Both ethanol and gamma aminobutyric acid (GABA) have been reported to inhibit hepatic regenerative activity in the rat. Because alcoholic beverages contain appreciable amounts of GABA, we documented whether the inhibitory effects of alcohol on the liver are derived from ethanol alone or the combination of ethanol plus GABA., Methods: Adult male Sprague-Dawley rats (n=6/group) were treated with either ethanol (3 g/kg), GABA (500 mg/kg) or ethanol plus GABA (3 kg and 500 mg/kg, respectively), beginning 1 h prior to a 70% partial hepatectomy and continued every 4 h thereafter for a total of 24 h. Rats were then sacrificed and hepatic regenerative activity was documented by 3H-thymidine incorporation into hepatic DNA., Results: DNA synthesis was significantly inhibited by ethanol (-37%, p<0.005) and GABA (-19%, p<0.05). Maximum inhibition was achieved with the combination of ethanol plus GABA (-52%, p<0.001). To determine whether the additive effects of ethanol plus GABA were mediated by ethanol-induced enhancement of hepatic GABA(A) receptor activity, additional rats (n=6/group) receiving the combination of ethanol plus GABA were pre-treated with a single injection of either ciprofloxacin (50 mg/kg), a GABA(A) receptor antagonist, or an equal volume of saline. In these experiments, ciprofloxacin pre-treatment prevented the inhibitory effects of the ethanol plus GABA combination., Conclusions: The results of this study indicate that the combination of ethanol plus GABA has a greater inhibitory effect on hepatic DNA synthesis following partial hepatectomy than ethanol alone. The clinical implication of this finding is that, when standardized for ethanol content, not all alcoholic beverages would be expected to have the same inhibitory effect on hepatic regeneration.

In order to document and compare proliferating cell nuclear antigen (PCNA) mRNA and protein levels with more traditional parameters of hepatic regenerative activity in a rat model, adult male Sprague-Dawley rats (4 to 6 per group) were killed at various times up to 96 hours after 70% partial hepatectomy. At each time interval, tissue PCNA mRNA abundance and protein levels were documented (by Northern and Western blot analysis, respectively) and compared with the results of PCNA immunostaining and 3H-thymidine incorporation into hepatic DNA. Tissue PCNA protein levels were also documented in additional groups of rats 12, 24, 36, and 48 hours after sham or 30% partial hepatectomy. PCNA mRNA expression after partial hepatectomy was variable: almost undetectable at 24 hours, levels returned to baseline at 36 hours, then fell again to low levels at 96 hours. PCNA protein levels remained stable for 36 hours, increased to fourfold above baseline (p < 0.01) at 48 hours, then remained elevated for the duration of the 96-hour study. Changes in PCNA by immunostaining were similar but tended to occur somewhat earlier (significant increases being detectable at 24 hours), whereas 3H-thymidine incorporation detected the earliest increases in DNA synthesis at 12 hours and peaked at 36 hours. Peak PCNA protein levels correlated with the extent (0%, 30%, or 70%) of hepatic resection. The results indicate that PCNA protein level as determined by Western blot analysis, but not PCNA mRNA expression, correlates with PCNA immunostaining and 3H-thymidine incorporation in the regenerating liver. These findings support the use of PCNA protein determinations as an additional quantitative measure of hepatic regenerative activity after partial hepatectomy in rats.

Recently, we reported that ciprofloxacin, an antimicrobial agent with gamma-aminobutyric acid (GABA(A)) receptor antagonist properties, significantly increases hepatic regenerative activity in animal models of alcohol-induced liver disease and cirrhosis. In the present study, we documented the effects of ciprofloxacin on survival and hepatic regeneration in a D-galactosamine (D-gal)-induced model of acute hepatic injury in rats. One hundred nineteen adult, male Sprague-Dawley rats (n = 19-20/group) were treated with intraperitoneal D-gal (total dose: 2.5 g/kg), followed by gastric gavage with either saline, ciprofloxacin (10, 50, or 100 mg/kg), norfloxacin (250 mg/kg), or intraperitoneal putrescine (300 micromol/kg), a potent hepatic growth promoter. Mortality rates were then documented over a 4-day period. An additional 45 rats (n = 15/group) received a sublethal dose of D-gal (1.0 g/kg), followed by gastric gavage with either saline or ciprofloxacin (100 mg/kg), or intraperitoneal putrescine (300 micromol/kg). In these rats, hepatic regenerative activity was documented at 12, 24, and 60 hours post-D-gal by 3H-thymidine incorporation into hepatic DNA and proliferating cell nuclear antigen (PCNA) staining. In the survival study, a dose-response effect of ciprofloxacin on survival was observed (ciprofloxacin: 10 mg/kg, 10%; 50 mg/kg, 26%; and 100 mg/kg, 35%) with the results in the 100-mg/kg-treated group being significant when compared with the 5% survival rate in saline-treated controls (P < .05). Survival figures in the norfloxacin- and putrescine-treated groups were not significantly improved (15% and 25%, respectively). In the regeneration study, compared with the D-gal + saline-treated control group, DNA synthesis rates at 60 hours were increased in the D-gal + ciprofloxacin and D-gal + putrescine groups (10.2 +/- 3.3 vs. 18.2 +/- 5.1 and 18.8 +/- 6.8 x 10(3) dpm/mg DNA respectively; P < .05). The results of PCNA staining also supported enhanced hepatic regeneration in the ciprofloxacin-treated group at 60 hours (saline, 13.4 +/- 3.7; ciprofloxacin, 47.4 +/- 7.3; and putrescine, 8.4% +/- 2.8% hepatocytes staining positive). Ciprofloxacin at a dose of 100 mg/kg significantly improves survival and hepatic regenerative activity in this animal model of acute hepatic injury.

Liver regeneration is an essential component of the reparative process following liver injury and surgical resection. It can be assessed by different tissue-based tests such as liver weights, mitotic counts, DNA contents and synthesis rates, immunohistochemical staining of nuclear antigens, gene expressions and certain protein levels or various serum-based tests that largely consist of specific enzyme determinations or documentation of certain proliferation markers. Although the simplest tissue-based test of liver regeneration is measurement of liver weights, these determinations are influenced by the extent of deposition of various materials not directly related to regeneration, such as lipids, glycogen and blood volumes. Because mitosis constitutes a very short segment of the cell cycle, mitotic counts are infrequently observed by light microscopy. Thymidine and BrdU incorporation into DNA are the reference tools for studying DNA synthesis, but their use requires pre-injection with radioactive isotopes or nucleotides which render them impractical for human studies. Flow cytometry is an accurate and objective method of monitoring hepatic regenerative activity but requires sophisticated equipment that is not generally available in many laboratories. Immunohistochemical staining for nuclear antigens (Ki-67, proliferating cell nuclear antigen [PCNA], DNA polymerase alpha and nucleolar organizer region [NOR] proteins) are acceptable and commonly used methods of monitoring regenerative activity but are subject to inter- and intra-observer variability. Gene expression rates such as Histone-3 mRNA abundance are hampered by the relatively low rates of gene transcription and the need for recombinant DNA technology. Protein and enzyme levels in liver tissues, such as putrescine, ornithine decarboxylase and thymidine kinase, are not precise and are confounded by the nutritional status of the host. While PCNA protein levels measured by immunoblot hold promise as a simple, accurate and reproducible marker of liver regeneration, additional studies are required to determine if this is a valid marker of regenerative activity in various models of hepatic injury and in humans. Of the serum-based determinations: thymidine kinase, ornithine decarboxylase, fibronectin, alpha fetoprotein, and early pregnancy factor offer practical and non-invasive tools to monitor liver regeneration, but the sensitivity and specificity of these tests have yet to be determined. In conclusion, many tissue and serum-based methods have been employed in clinical and experimental studies to assess liver regeneration; however, a gold standard has yet to be identified. Because of the disadvantages inherent in each method, and until a new, more accurate marker is identified, clinicians and scientists should incorporate a minimum of two independent markers in studies of liver regeneration.

The ability to document nuclear proliferation in the liver is essential to our understanding of hepatic regeneration and hepatocellular carcinoma. While numerous tests are available to provide such information in experimental animals, few can be applied to patients with liver disease. Ki-67 is a proliferating nuclear antigen present in replicating cells. Recent data indicates that staining for Ki-67 reflects nuclear proliferation in these tissues. To date, the technique has had only limited application to human liver tissues in formalin-fixed paraffin embedded tissue. In the present study, we documented Ki-67 staining in archival liver tissue from patients with mild chronic hepatitis, severe chronic hepatitis, inactive cirrhosis, hepatocellular carcinoma, and in normal livers. We found that Ki-67 staining was increased in patients with mild chronic hepatitis (labelling index 29 +/- 25), severe chronic hepatitis (labelling index 41 +/- 40), and hepatocellular carcinoma (labelling index 71 +/- 61), when compared to patients with inactive cirrhosis, (labelling index 1.4 +/- 3.1), and normal livers (labelling index 2.5 +/- 3.2). In conclusion, Ki-67 maybe useful tool to assess hepatocyte proliferation in formalin-fixed paraffin-embedded human liver tissue.

Quinolone antibiotics inhibit eukaryotic as well as prokaryotic cell growth and protein synthesis. To determine whether these properties adversely affect hepatic growth and recovery following surgical resection, five groups of healthy, adult male rats (n = 7-8/group) were treated for 10 days with equal volumes of either ofloxacin (50 mg/kg), fleroxacin (25 mg/kg), ciprofloxacin (25 mg/kg), norfloxacin (15 mg/kg) or sterile saline (controls) prior to 70% partial hepatectomy (PH) and daily thereafter until death. Restituted liver mass, DNA and protein synthesis rates were determined at 24, 48 and 72 h PH. The results of the study revealed that all parameters of hepatic regeneration were similar in the five study groups at each time interval. To ensure that an effect on hepatic regeneration was not dose-dependent, additional experiments were performed where 1, 10 and 100 mg/kg ciprofloxacin was administered and DNA synthesis was measured 24 h post-PH. Once again, the results were similar to sterile saline-treated controls. These findings suggest that the quinolone antibiotics are unlikely to have an adverse effect on hepatic recovery following surgical resection of the liver and are safe to use in that setting.

Changes in potential differences (PD) across hepatocyte membranes after partial hepatectomy may play an important role in hepatic homeostatic mechanisms and regenerative activity. To date, few studies have attempted to describe the extent and duration of such changes. In the present study, we documented PD values immediately before and for a 24-hour period after a partial hepatectomy (PHx) of 70% in healthy adult rats. We also documented PD changes after 30% and 90% PHx and PD values in different lobes of the same liver before and after PHx. Our findings showed that the liver depolarizes promptly (within 5 minutes of PHx) and that changes in PD are sustained for approximately 18 hours before returning to baseline values. We also observed that the magnitude of hepatic depolarization correlates with the extent of PHx. Finally, we did not observe regional differences in PD recordings from various lobes before and after PHx. These findings enhance our understanding of the physiological changes that occur in regenerating livers after PHx in rats.

To determine whether the inhibitory effects of ethanol on hepatic regeneration could be prevented by ciprofloxacin, a fluroquinolone antibiotic with gamma-aminobutyric acid (GABAA), receptor antagonist properties, adult, male Sprague-Dawley rats (n = 6-8/group) received intraperitoneal injections of saline, putrescine (a hepatic growth promoter, 50 mg/kg), or ciprofloxacin (100 mg/kg), followed 1 hour later by gastric gavage with saline or ethanol (5 g/kg). One hour post-gavage, all rats underwent a 70% partial hepatectomy (PHx). Hepatic regenerative activity was documented 24 hours post-PHx by 3H-thymidine incorporation into hepatic DNA (DNA synthesis), proliferating cell nuclear antigen staining, and hepatic tissue putrescine levels. Compared with healthy controls, DNA synthesis rates were significantly lower in ethanol-gavaged/saline-treated rats (22.7 +/- 4.4 x 10(3) vs. 12.3 +/- 6.9 x 10(3) DPM/mg DNA, respectively, P < .001) but unaltered in putrescine-(18.8 +/- 3.4 x 10(3) DPM/mg DNA) and ciprofloxacin-treated (18.3 +/- 2.6 x 10(3) DPM/mg DNA) rats. Hepatic proliferating cell nuclear antigen staining supported these findings. Hepatic putrescine levels also correlated with DNA synthesis data, being decreased in ethanol-gavaged/saline-treated rats (86 +/- 14 pmoles/mg tissue) compared with healthy controls (120 +/- 12 pmoles/mg, P < .01), ethanol-gavaged/putrescine-treated (112 +/- 14 pmoles/mg, P < .05) and ethanol-gavaged/ciprofloxacin-treated (125 +/- 17 pmoles/mg, P < .05) rats. To determine whether these effects resulted from GABAA receptor-mediated changes in liver membrane potentials, intracellular membrane potentials were recorded before and 1 hour after PHx in healthy control, ethanol-gavaged/saline-treated and ethanol-gavaged/ciprofloxacin-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this study was to determine whether all commercially available forms of interferon alfa (INF alpha) have the same inhibitory effect on hepatic regeneration and whether this inhibitory effect can be prevented by putrescine, a hepatic growth promotor. Adult male Sprague-Dawley rats (n = 92) received either IFN alpha-2a, 2b, n1, or saline, 0 and 18 hours after partial hepatectomy (PHx) or 16 hours before PHx. A subgroup of 29 rats being treated with IFn alpha-2a or saline also received putrescine (5, 50, or 500 mg/kg) 16 hours before PHx. Hepatic regeneration was documented by determining [3H]-thymidine incorporation into hepatic DNA (DNA synthesis), hepatic putrescine levels, and, in selected cases, ornithine decarboxylase (ODC) activity at 24 hours after PHx. The results of the study showed that hepatic regeneration was unaffected when IFN alpha was administered 0 and 18 hours after PHx. When administered at -16 hours, only IFN alpha-2a significantly inhibited DNA synthesis and was associated with decreased hepatic putrescine levels. Inhibition was dose-dependent in that a 10-fold increase in IFN alpha-2a caused a further decrease in both DNA synthesis and hepatic putrescine levels. At the higher dose, IFN alpha-2b and n1 also inhibited DNA synthesis and lowered hepatic putrescine levels and ODC activity. Exogenous putrescine (5 and 50 mg/kg) restored hepatic regenerative activity to normal but was toxic at high concentrations (500 mg/kg). These data indicate that not all commercially available forms of IFN alpha inhibit hepatic regeneration in the rat to the same extent.

Liver regeneration is an essential component of the recovery period after partial hepatectomy. Unfortunately, tests that accurately predict regenerative activity in the postoperative period have yet to be described. This study was designed to determine whether the extent of hepatic fibrosis correlates with liver regeneration activity after partial hepatectomy in rats with carbon tetrachloride-induced liver disease. Two groups of adult male Sprague-Dawley rats (12 to 30/group) were treated for 20 to 22 wk with weekly intragastric doses of carbon tetrachloride or vehicle. All rats then underwent 70% hepatectomy while under ether anesthesia. Liver regeneration activity was determined at 24 and 48 hr by [3H]thymidine incorporation into DNA. Hepatic fibrosis was calculated at the time of partial hepatectomy by automated image analysis on Van Gieson-stained liver tissue. Although a significant inverse correlation was found between the extent of hepatic fibrosis and DNA synthesis when all rats were considered (carbon tetrachloride-treated and vehicle-treated) at 24 and 48 hr after partial hepatectomy (r = -0.4943 and -0.7396, respectively; p < 0.05), no such correlation existed when carbon tetrachloride-treated rats were considered independently (r = -0.3231 and -0.0910 at 24 and 48 hr, respectively). In conclusion, we believe that in diseased livers, preoperative quantitation of hepatic fibrosis on automated image analysis does not serve as a useful predictor of liver regeneration activity.

Background: gamma-Aminobutyric acid (GABA) is a potent inhibitory neurotransmitter with growth-regulatory properties. In fulminant hepatic failure, a condition in which hepatic regeneration may be impaired, systemic serum GABA concentrations are markedly elevated. The present study was designed to determine whether increased amounts of circulating GABA interfere with hepatic regenerative activity., Methods: Exogenous GABA or isotonic saline was administered to adult male rats (n = 6-12/group) 16 hours before partial hepatectomy and twice daily for 1-3 days thereafter. The hypertrophic and hyperplastic components of hepatic regeneration were determined by calculation of the restitution of liver mass, [14C]leucine incorporation into protein (protein synthesis), and [3H]thymidine incorporation into hepatic DNA (DNA synthesis)., Results: Exogenous GABA impaired restitution of liver mass (GABA vs. controls, day 3: 76% +/- 7% vs. 90% +/- 9%, mean +/- SD) (P < 0.005) and the rate of protein synthesis (GABA vs. controls, day 1: 379 +/- 39 dpm/mg protein vs. 564 +/- 67 dpm/mg protein) (P < 0.01) without interfering with DNA synthesis. Supplemental administration of corticosterone and putrescine restored protein synthesis rates to normal in GABA-treated rats., Conclusions: These results indicate that elevated serum GABA concentrations interfere with the hypertrophic component of hepatic regeneration following partial hepatectomy in rats.

There are conflicting data regarding the ability of the liver to regenerate after partial hepatectomy in animals and humans with cirrhosis. The purpose of this study was to document liver regeneration after partial hepatectomy in a carbon tetrachloride rat model of cirrhosis and to determine whether exogenous putrescine, a polyamine that has been reported to stimulate liver regeneration in animal models of acute liver failure, enhances regenerative activity in cirrhosis. Liver fibrosis and cirrhosis were produced by weekly intragastric gavage with carbon tetrachloride in 130 adult male rats. Vehicle-gavaged rats (n = 12) served as healthy controls. At surgery and at 4 and 8 hr after 70% hepatectomy, rats received normal saline solution or 1 or 10 mg/kg putrescine by intraperitoneal injection. Another group (n = 32) of carbon tetrachloride-treated rats was given putrescine (100 mg/kg) or normal saline solution twice daily for 10 days before partial hepatectomy and at 0, 4 and 8 hr after partial hepatectomy. Liver regeneration was documented 24 and 48 hr after partial hepatectomy on the basis of restitution of liver mass, ornithine decarboxylase activity and [3H]thymidine incorporation into liver DNA. Automated image analysis of the resected liver specimens separated carbon tetrachloride-treated rats into two subgroups: those with bridging fibrosis (fibrotic group) and those with micronodular cirrhosis (cirrhotic group). Restitution of liver mass and ornithine decarboxylase activity at 24 and 48 hr after partial hepatectomy were similar to carbon tetrachloride-treated rats (both fibrotic and cirrhotic) and vehicle-treated healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamines and their principal metabolite, gamma-aminobutyric acid (GABA), modulate eukaryotic cell growth. To determine whether the liver possesses specific polyamine transport sites and whether changes occur to these or GABA transport sites during hepatic regeneration, suspensions of rat hepatocytes derived from in situ collagenase perfusions of livers at times 0, 24, 48, and 72 h post-partial hepatectomy were incubated at 4, 20, and 37 degrees C with various concentrations of the following ligands: [3H]putrescine, [3H]spermidine, [14C]spermine, and [3H]GABA together with or without excess unlabeled ligand, KCN, ouabain, or digitoxigenin. Of the ligands studied, only [14C]spermine and [3H]GABA were associated with specific binding to hepatocytes derived from nonregenerating livers. Spermine binding correlated with the concentration of hepatocytes in the incubation mixture and reached equilibrium within 60 min. The approximate affinity constant (KD) was 5.5 x 10(-5) mol/10(6) hepatocytes, and maximum number of binding sites (Bmax) was 1.8 +/- 1.2 x 10(-7) mol.10(6) hepatocytes-1.min-1. Binding was neither temperature nor sodium dependent and was not inhibited by KCN, ouabain, digitoxigenin, other polyamines, or GABA. Aside from a 43% decrease in spermine binding at 24 h post-partial hepatectomy [5.1 +/- 1.1 vs. 8.9 +/- 3.1 x 10(3) disintegrations per minute (dpm)/10(6) hepatocytes at time 0, P less than 0.05] and a 39% decrease in GABA binding (3.4 +/- 1.3 vs. 5.5 +/- 1.9 x 10(3) dpm/10(6) hepatocytes, P less than 0.05), there were no significant changes in ligand binding during hepatic regeneration.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of the present study was to determine whether changes to the gut flora that occur following norfloxacin-induced selective bowel decontamination alter hepatic regenerative activity. Adult rats (n = 6 per group) were treated with norfloxacin (10 mg/day) or vehicle for 10 days before 70% partial hepatectomy. Hepatic regenerative activity was determined 24 hours after surgery by documenting restitution of liver mass, [3H]thymidine incorporation into DNA, and ornithine decarboxylase activity in the liver. The results of the study revealed that hepatic regeneration was unaffected by norfloxacin therapy. Thus, selective bowel decontamination with norfloxacin does not alter hepatic regenerative activity following partial hepatectomy in the rat.

Previous studies have reported conflicting results regarding the effect of ethanol on hepatic regeneration. The purpose of the present study was to determine whether long-term, voluntary consumption of ethanol, within the range reported in humans, has an effect on hepatic regenerative activity in rats following partial hepatectomy. Ninety-four adult male Sprague-Dawley rats (n = 3-9/group) were studied. Based on the amount of 9% ethanol consumed over a 50-day period, low ethanol intake (0.1-1.9 g.kg-1.d-1) and high ethanol intake (2.0-4.0 g.kg-1.d-1) groups were identified. Control groups consisted of rats provided with propylene glycol in equivalent caloric amounts to the ethanol consumed by high ethanol intake rats (isocaloric group) and rats served water only (ad libitum group). An additional two groups from which ethanol was removed 5 days prior to surgery were also studied (low ethanol grace and high ethanol grace). Hepatic regeneration was determined by restitution of liver weight, [3H]thymidine incorporation into DNA, and [14C]leucine incorporation into protein 24, 48, and 72 h following partial (70%) hepatectomy. The results of the study revealed no significant differences in the rate of hepatic regeneration between low and high ethanol consuming rats or between either of these groups and isocaloric or ad-libitum fed control groups. Regeneration in low ethanol grace and high ethanol grace groups were also similar to each other and controls. Moreover, there was no correlation between mean ethanol consumption per rat and restitution of liver weight, [3H]thymidine incorporation into DNA, or [14C]leucine incorporation into protein by the regenerating liver (r = 0.0716, -0.1637, and 0.1395, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)