The Effects of Colectomy on Immediate–Early Proto-Oncogene Expression and Hepatic Regeneration in the Rat

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 postcolectomy. 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/μ g DNA; sham-colectomy controls, 14.8 ± 1.4 dpm/μg 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.     

Regenerative activity and liver function following partial hepatectomy in the rat using (31)P-MR spectroscopy

The aim of the present study was to determine whether alterations in hepatic energy expenditure following partial hepatectomy (PHx), as documented by in vivo hepatic (31)P-MRS, correlate with standard parameters of hepatic regeneration and/or liver function. In addition, we sought to determine whether changes in hepatic energy levels are proportional to the extent of hepatic resection. Adult male Sprague-Dawley rats (4-7 per group) underwent a 40%, 70%, or 90% PHx or sham surgeries. Magnetic resonance spectroscopy (MRS) examinations were performed on each animal 24 or 48 hours thereafter. After MRS examinations, [(3)H]thymidine incorporation into hepatic DNA, proliferating cell nuclear antigen (PCNA) protein expression, and serum bilirubin determinations were performed on each rat. Twenty-four hours following surgery, rats that had undergone 70% PHx had unchanged adenosine triphosphate (ATP) levels but significantly lower ATP/inorganic phosphate (Pi) ratios (P <.05), whereas, at 48 hours post-PHx, both ATP and ATP/Pi levels were lower than in sham- and nonoperated controls (P <.05). Hepatic regeneration and liver dysfunction mirrored these changes; correlations existed between ATP/Pi ratios and [(3)H]thymidine incorporation (r = -0.61, P <.005), PCNA protein expression (r = -0.62, P <.005), and serum bilirubin (r = -0.49, P <.05). For rats that had undergone graded resections, depleted energy levels 48 hours post-PHx were proportional to the extent of resection, degree of enhanced regenerative activity, and liver dysfunction. In conclusion, (31)P-MRS-generated ATP/Pi index is a noninvasive, robust determination that correlates with standard parameters of hepatic regeneration and function.     

Epidermal growth factor and insulin-induced deoxyribonucleic acid synthesis in primary rat hepatocytes is phosphatidylinositol 3-kinase dependent and dissociated from protooncogene induction

The mitogenic response to insulin and epidermal growth factor (EGF) was studied in subconfluent and confluent cultures of primary rat hepatocytes. In subconfluent cultures, wortmannin, LY294002, and rapamycin reversed insulin- and EGF-induced [3H]thymidine incorporation into DNA. The mitogen-activated protein kinase (MAPK) kinase 1 (MEK1) inhibitor PD98059 was without significant effect on either insulin- or EGF-induced [3H]thymidine incorporation. Insulin treatment did not alter levels of messenger RNAs (mRNAs) for c-fos, c-jun, and c-myc. EGF induced an increase in c-myc, but not c-fos or c-jun, mRNA levels in subconfluent hepatocyte cultures. This increase in c-myc mRNA was abolished by PD98059. In confluent cells that could not be induced to synthesize DNA, EGF treatment also promoted an increase in c-myc mRNA to levels seen in subconfluent cultures. This increase was also abrogated by PD98059. These data indicate that in primary rat hepatocyte cultures, 1) the phosphoinositol 3-kinase pathway, perhaps through p70s6k activation, regulates DNA synthesis in response to insulin and EGF; 2) the MAPKpathway is not involved in insulin- and EGF-induced DNA synthesis; and 3) p44/42 MAPKs are involved the induction of c-myc mRNA levels, although this induction is not required for DNA synthesis. These studies define two distinct signal transduction pathways that independently mediate growth-related responses in a physiologically relevant, normal cell system.     

Prognostic significance of the expression of c-fos,c-jun and c-erbB-1 oncogene products in human squamous cell lung carcinomas

The expression of the oncogenes c-fos, c-jun, c-myc, c-erbB-1 and c-erbB-2 at the protein level was analyzed in squamous cell lung carcinomas of 121 patients by means of immunohistochemistry. Patients with overexpression of proteins encoded by the oncogenes c-fos, c-jun and c-erbB-1 had significantly shorter survival times than these without overexpression of these oncogene products (c-fos:p=0.009; c-jun:p=0.029; c-erbB-1:p=0.018). No significant correlations were found between the expression of c-myc and c-erbB-2 products and the survival of the patients. In addition to the univariate analyses (Kaplan-Meier-estimates) multivariate analyses (Cox-regression-model) revealed that protein expression of the oncogenes c-fos, c-jun and c-erbB1 are significant prognostic factors in addition to staging.     

Light ethanol consumption enhances liver regeneration after partial hepatectomy in rats

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.     

地尔硫卓对增殖血管平滑肌细胞的原癌基因表达的影响

目的观察地尔硫卓（Dil）对增殖血管平滑肌细胞（VSMC）的原癌基因c-myc、c-fos、c-jun和ras mRNA表达的影响。方法将组织贴块法培养的大鼠胸主动脉VSMC随机分为5组,即空白组、模型组和Dil1、2、3组（浓度分别为10^-5、10^-6、10^-7mol/L）,应用MTT检测增殖能力,用流式细胞术检测VSMC的增殖指数,用rt-PCR检测c-myc、c-fos、c-jun和ras mRNA的表达。结果与模型组比较各浓度Dil都能抑制VSMC增殖,PI值均显著下降（各组PI值分别为21.53±1.72、28.63±0.96、15.95±0.37、19.28±0.94、20.33±0.67;P〈0.05）;Dil1、2组c-myc、c-fos、c-jun mRNA的表达显著减少（模型组和Dil1、2组的c-myc/GAPDH值分别为2.454±0.03、1.509±0.05、1.660±0.04,c-fos/GAPDH值分别为0.0046±0.0004、0.0023±0.0003、0.0038±0.0005,c-jun/GAPDH值分别为1.950±0.03、1.077±0.03、1.725±0.03;P〈0.05）,rasmRNA的表达显著增加（模型组和Dil1、2组的ras/GAPDH值分别为1.941±0.03、3.811±0.02、2.501±0.02;P〈0.05）。结论Dil抑制VSMC增殖机制可能与下调原癌基因c-myc、c-fos、c-jun的表达和上调ras的表达有关。     

Effect of Qi-protecting powder （Huqi San） on expression of c-jun,c-fos and c-myc in diethylnitrosamine-mediated hepatocarcinogenesis

To study the inhibitory effect of Huqi San （Qi- protecting powder） on rat prehepatocarcinoma induced by diethylinitrosamine （DEN） by analyzing the mutational activation of c-fos proto-oncogene and over-expression of c-jun and c-myc oncogenes. METHODS： A Solt-Farber two-step test model of prehepatocarcinoma was induced in rats by DEN and 2-acetylaminofluorene （AAF） to investigate the modifying effects of Huqi San on the expression of c-jun, c-fos and c-myc in DEN-mediated hepatocarcinogenesis. Huqi San was made of eight medicinal herbs containing glycoprival granules, in which each milliliter contains 0.38 g crude drugs. T-glutamy-transpeptidase-isoenzyme （T-GTase） was determined with histochemical methods. Level of 8-hydroxydeoxyguanosine （OHdG） formed in liver and c-jun, c-fos and c-myc proto-oncogenes were detected by immunohistochemical methods. RESULTS： The level of 8-OHdG, a mark of oxidative DNA damage, was significantly decreased in the liver of rats with prehepatocarcinoma induced by DEN who received 8 g/kg body weight or 4 g/kg body weight Huqi San before （1 wk） and after DEN exposure （4 wk）. Huqi San- treated rats showed a significant decrease in number of T-GT positive foci （P 〈 0.001, prevention group： 4.96-0.72 vs 29.46-2.17; large dose therapeutic group： 7.53-0.88 vs 29.46-2.17）. On the other hand, significant changes in expression of c-jun, c-fos and c-myc were found in Huqi San-treated rats. CONCLUSION： Activation of c-jun, c-fos and c-myc plays a crucial role in the pathogenesis of liver cancer.Huqi San can inhibit the over-expression of c-jun, c-fos and c-myc oncogenes and liver preneolastic lesions induced by DEN.     

原癌基因在大鼠心肌梗死的表达及福辛普利的干预作用

目的 探讨大鼠心肌梗死（MI）时原癌基因的表达及幅辛普利对其影响。方法 用冠状动脉结扎法制成大鼠MI模型，分假手术组、梗死模型组、幅辛普利小剂量组、福辛普利大剂量组。在MI后24h和4w剪取心肌标本，用逆转录-聚合酶链式反应（RT-PCR）测定原癌基因c-myc、c-fas、c-jun的mRNA表达。结果 大鼠M124h后：c-myc、c-fos、c-jan高表达，福辛普利能抑制其表达。大鼠M14w后：c-myc、c-fos、c-jun的表达基本停止，福辛普利对其表达无明显影响。结论 原癌基因在AMI的早期有高表达，血管紧张素转换酶抑制剂（ACEI）对其有明显抑制作用，AMI后尽早应用ACEI对防治心室重构具有重要意义。     

Gonadotropin induction of c-fos and c-myc expression and deoxyribonucleic acid synthesis in rat granulosa cells

Although gonadotropins stimulate ovarian granulosa cells to proliferate and differentiate into steroidogenic cells, little is known about the molecular mechanisms by which gonadotropins induce these fundamentally different responses. In this study the acute effects of PMSG on protooncogene expression, DNA synthesis, and steroid secretion were examined. The levels of c-fos, c-myc, and beta-actin mRNA were measured in total RNA samples from granulosa cells by quantitative polymerase chain reaction. PMSG increased the mRNA levels of c-fos, c-myc, and beta-actin within 15 min. Fos and myc proteins were localized within granulosa cells by immunocytochemistry. Less than 10% of granulosa cells stained for c-fos or c-myc proteins in the control samples. In contrast, approximately 40% of the cells stained for these protooncogene proteins 30 min after PMSG injection (P less than 0.05). These values declined to about 10% of the cells 60 min after PMSG injection. DNA synthesis, as estimated by [3H]thymidine incorporation, increased 30 and 60 min after PMSG (P less than 0.05). 17 beta-Estradiol and progesterone synthesis did not change within 60 min of PMSG injection. These data demonstrate that 1) c-fos and c-myc are expressed in ovarian granulosa cells; 2) the expression of the genes encoding c-fos, c-myc, and beta-actin is rapidly increased by gonadotropin; and 3) the increase in the corresponding products of the c-fos and the c-myc genes precedes an increase in DNA synthesis and steroid production. These data suggest that the expression of c-fos and c-myc may be a part of the molecular mechanism through which gonadotropins regulate granulosa cell function.     

Systemic Short-Chain Fatty Acids Rapidly Alter Gastrointestinal Structure, Function, and Expression of Early Response Genes

Luminal and systemic short chain fatty acids (SCFA) stimulate mucosal proliferation but the mechanism(s) is unclear. This study examined acute effects of systemic SCFAs on gastrointestinal structure and function and signals potentially mediating SCFA-induced mucosal proliferation. Male Sprague-Dawley rats (246 ± 2 g) received nutrients as either standard total parenteral nutrition (TPN) or an isoenergetic, isonitrogenous formulation containing SCFAs (TPN + SCFA). Animals were randomized to one of five treatments: standard TPN for 72 hr, TPN + SCFA for 72 hr, or standard TPN followed by TPN + SCFA for the final 6, 12, and 24 hr. SCFAs reduced (P < 0.003) ileal protein within 6 hr. Jejunal GLUT2 expression was increased (P = 0.0001) in all SCFA groups and ileal GLUT2 protein in the 6-, 12-, and 24-hr SCFA groups (P < 0.05). SCFAs increased (P < 0.003) ileal proglucagon abundance following 6, 12, and 24 hr, and plasma GLP-2 concentration following 12 hr (P < 0.03). Jejunal c-myc expression was increased (P < 0.001) following 6, 12, and 24 hr of SCFAs. SCFAs increased ileal c- myc , c- jun, and c-fos expression following 24 hr (P < 0.02), 12 hr (P < 0.05) and 6, 12, and 24 hr (P = 0.0001), respectively. In conclusion, systemic SCFAs increase plasma GLP-2 and ileal proglucagon mRNA, GLUT2 expression and protein, and c-myc, c-jun, and c-fos expression.     

Regulation of c-fos, c-jun, jun-B, and c-myc messenger ribonucleic acids by gonadotropin and growth factors in cultured pig Leydig cell.

The nuclear protooncogenes have been implicated in the coordinate regulation of gene expression during cell proliferation and differentiation. Previous work has shown that LH and human h CG as well as several growth factors including epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), transforming growth factor-beta, and insulin-like growth factor-I play a role in Leydig cell differentiated functions. To evaluate the possibility that protooncogenes mediate long term effects of these factors, their action on the levels of c-fos, c-jun, jun-B, and c-myc messenger (m) RNAs was studied. hCG (10(-9) M) produced a time-dependent increase in c-fos (9-fold), jun-B (18-fold) and c-myc (5-fold) mRNA levels but did not affect c-jun. The concentration of hCG required for half-maximal stimulation (ED50 = 7 +/- 4 x 10(-12) M) was similar to that required to induce half-maximal testosterone production. At optimal concentrations, the effects of EGF and bFGF on c-fos and jun-B mRNAs were lower than those induced by hCG, but their effects on c-myc mRNA were higher. In addition, they stimulated c-jun. Moreover, EGF and bFGF potentiated the effects of hCG on c-fos and jun-B, whereas hCG potentiated the action of growth factors on c-jun. Transforming growth factor-beta increased only jun-B mRNA, whereas insulin-like growth factor I increased c-fos, jun-B, and c-myc but less effectively than hCG. Lastly, the phorbol ester phorbol 12-myristate 13-acetate increased the level of the four protooncogene mRNAs, and its effects on c-fos and c-myc were significantly higher than those produced by hCG. These data indicate that the regulation of protooncogene mRNAs in normal Leydig cells is multifactorial. They also show differential responsiveness of the members of the Jun family to several factors. Our results are consistent with the hypothesis that the Fos and Jun families of regulatory proteins could play a role in mediating long term responses to the complex array of hormones and growth factors to which Leydig cells are exposed in vivo.     

Adenine nucleotide changes in the remnant liver: An early signal for regeneration after partial hepatectomy

Liver regeneration after partial hepatectomy (PHx) is orchestrated by multiple signals from cytokines and growth factors. We investigated whether increased energy demand on the remnant liver after PHx contributes to regenerative signals. Changes in the tissue's energy state were determined from adenine nucleotide levels. Adenosine triphosphate (ATP) levels in remnant livers decreased markedly and rapidly (to 48% of control by 30 seconds post-PHx) and remained significantly lower than those in sham-operated controls for 24 to 48 hours. The ATP decrease was not reflected in corresponding increases in adenosine diphosphate (ADP) and adenosine monophosphate (AMP), resulting in a marked decline in total adenine nucleotides (TAN). We found no evidence of mitochondrial damage or uncoupling of oxidative phosphorylation. Multiple lines of evidence indicated that the decline in TAN was not caused by increased energy demand, but by ATP release from the liver. The extent of ATP loss was identical after 30% or 70% PHx, whereas fasting or hyperglycemia, conditions that greatly alter energy demand for gluconeogenesis, affected the ATP/ADP decline but not the loss of TAN. Presurgical treatment with the alpha-adrenergic antagonist phentolamine completely prevented loss of TAN, although changes in ATP/ADP were still apparent. Importantly, phentolamine treatment inhibited early signaling events associated with the priming stages of liver regeneration and suppressed the expression of c-fos. Pretreatment with the purinergic receptor antagonist suramin also partly suppressed early regenerative signals and c-fos expression, but without preventing TAN loss. CONCLUSION: The rapid loss of adenine nucleotides after PHx generates early stress signals that contribute to the onset of liver regeneration.     

c-fos and c-jun mRNA Expression in Activated Cord and Adult Lymphocytes: An Analysis by Northern Hybridization

Background and Objectives: To further analyze the neonatal immune response to an antigenic challenge such as blood transfusion, c-fos and c-jun mRNA expression were analyzed in twelve in-vitro-stimulated normal cord blood and ten in-vitro-stimulated normal adult peripheral blood lymphocyte samples. Materials and Methods: Lymphocyte samples were stimulated by either the mitogen phytohemagglutinin (PHA) or the monoclonal antibody αCD3. Proliferation rate and Northern blot hybridization were employed. Results: Cord lymphocytes revealed a greater proliferation rate with PHA and αCD3 than adult lymphocytes (p=0.0081 and 0.0023, respectively). In addition, Northern blot analysis of cord and adult samples revealed similar maximal increases in c-fos (99±15 and 126±11%, p=0.0126) and c-jun (123±9 and 185±38%, p=0.0291) mRNA expression, respectively, as early as 15 min postαCD3 stimulation. Adult lymphocytes showed an equivalent increase in mRNA expression of c-fos and c-jun (140±25 and 155±31%) at 30 min post-PHA stimulation, while cord lymphocyte maximum c-fos and c-jun expression (82±6 and 142±12%) occurred at 15 min post-PHA stimulation (c-fos, p=0.0354; c-jun, p=0.0112). Conclusion: Although cord lymphocyte proliferation rates were significantly greater than those of adult lymphocytes following stimulation, lymphocyte activation, as analyzed by c-fos and c-jun mRNA expression, appears similar in both cord and adult samples. We conclude that cord lymphocyte activation exhibits an adult-type profile.     

同型半胱氨酸对球囊损伤大鼠颈动脉原癌基因表达的影响

目的:观察高蛋氨酸饮食诱导的高同型半胱氨酸(HCY)血症对大鼠颈动脉球囊损伤后血管组织原癌基因c-fos及c-jun的信使核糖核甙(mRNA)表达的影响,探讨其使血管成形术后新内膜过度增生的机制。方法:将12周龄健康雄性SD大鼠30只,随机分为对照组(普通饲料),10只,低蛋氨酸饮食组(1.2％蛋氨酸),10只,高蛋氨酸组(含2.0％蛋氨酸),10只,喂养4周后,以2F的球囊导管损伤左颈总动脉内皮的方法建立大鼠颈动脉球囊损伤模型,并以右颈总动脉作为对照(未行动脉球囊损伤),血管内皮损伤后1小时,处死动物,取颈总动脉,立即液氮冻存备用,采用RT-PCR方法检测血管组织c-fos及c-jun的mRNA表达情况,并做半定量分析。结果:低及高蛋氨酸组血浆HCY浓度明显高于饮食对照组(P<0.01),球囊损伤左颈总动脉各组组织的c-fos及c-jun mRNA表达均显著高于未损伤的右颈总动脉的(P<0.01),低蛋氨酸组和高蛋氨酸组c-fos及c-jun mRNA的表达均高于对照组的(P<0.01),高蛋氨酸组的c-fos及c-jun的mRNA表达明显高于低蛋氨酸组的(P<0.05)。结论:同型半胱氨酸能上调血管内皮损伤后动脉组织原癌基因c-fos及c-jun的mRNA的表达,且呈浓度依赖性,可能是其促进血管成形术后新内膜过度增生的机制之一。     

瓜蒌皮提取物对PDGF-BB所致血管平滑肌细胞增殖周期的影响

目的 研究瓜蒌皮提取物对血小板源生长因子BB所致血管平滑肌细胞增殖周期的影响并探讨其可能机制.方法 组织块贴块法培养SD大鼠胸主动脉平滑肌细胞,3H-TdR掺入观察瓜蒌皮提取物(10、20和30mg/L)对血小板源生长因子BB(20 μg/L)所致血管平滑肌细胞DNA合成的影响;流式细胞仪分析细胞增殖周期;real time RT-PCR检测血管平滑肌细胞中c-fos、c-myc mRNA表达.结果 血小板源生长因子BB可明显升高细胞每分钟脉冲数(P＜0.01),并增加S期细胞比例而降低G0/G1期细胞比例(P＜0.01),并上调c-fos、c-myc mRNA表达(P＜0.01).瓜蒌皮提取物各浓度组均明显抑制血小板源生长因子BB诱导的每分钟脉冲数升高(P＜0.01),降低S期细胞比例而升高G0/G1期细胞比例,明显下调血小板源生长因子BB所致的c-fos、c-myc mRNA高表达(P＜0.01).结论 瓜蒌皮提取物通过阻止血管平滑肌细胞由G0/G1期进入S期而抑制血小板源生长因子BB所致的增殖,其作用机制可能与降低细胞内c-fos、c-myc mRNA高表达有关.     

Altered lysophosphatidic acid (LPA) receptor expression during hepatic regeneration in a mouse model of partial hepatectomy

Background

Hepatic regeneration requires coordinated signal transduction for efficient restoration of functional liver mass. This study sought to determine changes in lysophosphatidic acid (LPA) and LPA receptor (LPAR) 1–6 expression in regenerating liver following two-thirds partial hepatectomy (PHx).

Methods

Liver tissue and blood were collected from male C57BL/6 mice following PHx. Circulating LPA was measured by enzyme-linked immunosorbent assay (ELISA) and hepatic LPAR mRNA and protein expression were determined.

Results

Circulating LPA increased 72 h after PHx and remained significantly elevated for up to 7 days post-PHx. Analysis of LPAR expression after PHx demonstrated significant increases in LPAR1, LPAR3 and LPAR6 mRNA and protein in a time-dependent manner for up to 7 days post-PHx. Conversely, LPAR2, LPAR4 and LPAR5 mRNA were barely detected in normal liver and did not significantly change after PHx. Changes in LPAR1 expression were confined to non-parenchymal cells following PHx.

Conclusions

Liver regeneration following PHx is associated with significant changes in circulating LPA and hepatic LPAR1, LPAR3 and LPAR6 expression in a time- and cell-dependent manner. Furthermore, changes in LPA–LPAR post-PHx occur after the first round of hepatocyte division is complete.     

Acute liver CCl(4) intoxication causes low HSP70 gene expression and a delayed transition through the cell cycle in aged rats

Since there is still debate about the ability of the aged liver to regenerate, we compared some aspects of this response in young, adult and old rodents. 2, 6, 12 and 19-month-old rats were intraperitoneally injected with CCl(4) (3mg/kg) or left untreated (CT) and killed either 2h (group A) or 24h (group B) after intoxication. Liver injury was checked histologically and by assaying transaminases. mRNA levels of albumin (Alb), c-fos, c-myc, hepatocyte growth factor (HGF), transforming growth factor (TGF)-alpha and TGF-beta1 were also analyzed. Heat shock protein (HSP)70 gene expression was evaluated, and liver GSH content. Transaminases and histology show more damage in aged rats. Alb mRNA was reduced starting at 12 months in group A and at all ages in group B; c-fos and c-myc mRNAs reached the highest levels in 6-month-old rats and the lowest in those aged 12 and 19 months of group A. In group B, c-fos was detectable only in 6-month animals, but c-myc at all ages. HGF, TGF-alpha and TGF-beta1 mRNAs were up-regulated in treated rats, but to a lesser extent in the aged. HSP70 mRNA, absent in CT, was significantly increased at the age of 6 months, undetectable in the oldest rats in group A; in group B it was only visible in 6-month animals. GSH content was reduced with aging. In conclusion, during aging the liver regenerative machinery is preserved but its activation is reduced and delayed.