HGF/c-Met signaling promotes liver progenitor cell migration and invasion by an epithelial-mesenchymal transition-independent, phosphatidyl inositol-3 kinase-dependent pathway in an in vitro model.

Oval cells constitute an interesting hepatic cell population. They contribute to sustain liver regeneration during chronic liver damage, but in doing this they can be target of malignant conversion and become tumor-initiating cells and drive hepatocarcinogenesis. The molecular mechanisms beneath either their pro-regenerative or pro-tumorigenic potential are still poorly understood. In this study, we have investigated the role of the HGF/c-Met pathway in regulation of oval cell migratory and invasive properties. Our results show that HGF induces c-Met-dependent oval cell migration both in normal culture conditions and after in vitro wounding. HGF-triggered migration involves F-actin cytoskeleton reorganization, which is also evidenced by activation of Rac1. Furthermore, HGF causes ZO-1 translocation from cell-cell contact sites to cytoplasm and its concomitant activation by phosphorylation. However, no loss of expression of cell-cell adhesion proteins, including E-cadherin, ZO-1 and Occludin-1, is observed. Additionally, migration does not lead to cell dispersal but to a characteristic organized pattern in rows, in turn associated with Golgi compaction, providing strong evidence of a morphogenic collective migration. Besides migration, HGF increases oval cell invasion through extracellular matrix, a process that requires PI3K activation and is at least partly mediated by expression and activation of metalloproteases. Altogether, our findings provide novel insights into the cellular and molecular mechanisms mediating the essential role of HGF/c-Met signaling during oval cell-mediated mouse liver regeneration.

EGFR is dispensable for c-Met-mediated proliferation and survival activities in mouse adult liver oval cells.

Liver progenitor cells rise as potential critical players in hepatic regeneration but also carcinogenesis. It is therefore mandatory to define the signals controlling their activation and expansion. Recently, by using a novel in vitro model of oval cell lines expressing a mutant tyrosine kinase-inactive form of c-Met we demonstrated that autocrine c-Met signalling plays an essential role in promoting oval cell survival. Here, we investigated the significance of the epidermal growth factor receptor (EGFR) signalling in oval cell proliferation and survival, as well as a potential functional crosstalk between the c-Met and the EGFR pathways. We found an autocrine activation of the EGFR-triggered pathway in Met(flx/flx) and Met(-/-) oval cells as judged by constitutive expression of the EGFR ligands, transforming growth factor-alpha (TGF-α) and heparin-binding EGF like growth factor (HB-EGF), and activation of EGFR. On the other hand, treatment with AG1478, a specific inhibitor of EGFR, effectively blocked endogenous and EGF-induced proliferation, while increased serum withdrawal and transforming growth factor-beta (TGF-ß)-induced apoptosis. These results suggest that constitutively activated EGFR might promote oval cell proliferation and survival. We found that hepatocyte growth factor (HGF) does not transactivate EGFR nor EGF transactivates c-Met. Furthermore, treatment with AG1478 or EGFR gene silencing did not interfere with HGF-mediated activation of target signals, such as protein kinase B (AKT/PKB), and extracellular signal-regulated kinases 1/2 (ERK 1/2), nor did it have any effect on HGF-induced proliferative and antiapoptotic activities in Met(flx/flx) cells, showing that HGF does not require EGFR activation to mediate such responses. EGF induced proliferation and survival equally in Met(flx/flx) and Met(-/-) oval cells, proving that EGFR signalling does not depend on c-Met tyrosine kinase activity. Together, our results provide strong evidence that in normal, untransformed oval cells, c-Met and EGFR represent critical molecular players to control proliferation and survival that function independent of one another.

[Validation of the Spanish version of the attention deficit hyperactivity disorder adult screening scale (ASRS v. 1.1): a novel scoring strategy]. / Validacion al espanol de la escala de cribado del trastorno por deficit de atencion/hiperactividad en adultos (ASRS v. 1.1): una nueva estrategia de puntuacion.

INTRODUCTION: Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric disorder in the adulthood. It's diagnosis is a complex process in which a screening tool can be useful. AIM: To analyze the six-question Adult ADHD Self-Report Scale (ASRS v. 1.1) validity in an outpatient clinical context. SUBJECTS AND METHODS: We performed a case-control study, involving 90 patients with ADHD and 90 controls without ADHD. They were outpatient treated in a program for adults ADHD in a hospital. The clinical disorder diagnosis was measured by the Conners Adult ADHD Diagnostic Interview. We analyzed the test accuracy for different ways to score and cut-offs. RESULTS: We found the best psychometric characteristics of ASRS v. 1.1 using a quantitative ranking between 0 and 24 points, setting as cut-off 12 points. We observed a sensitivity of 96.7%, specificity 91.1%, positive predictive value 91.6% negative predictive value 96.5%, kappa index 0.88 and area under the curve 0.94 (odds ratio = 297.3; 95% confidence interval = 76.2-1,159). CONCLUSION: The ASRS is a valid and useful tool for the adult ADHD screening in the clinical context.

Activation of caspases occurs downstream from radical oxygen species production, Bcl-xL down-regulation, and early cytochrome C release in apoptosis induced by transforming growth factor beta in rat fetal hepatocytes.

Most of the morphologic changes that are observed in apoptotic cells are caused by a set of cysteine proteases (caspases) that are activated during this process. In previous works from our group we found that treatment of rat fetal hepatocytes with transforming growth factor beta1 (TGF-beta1) is followed by apoptotic cell death. TGF-beta1 mediates radical oxygen species (ROS) production that precedes bcl-xL down-regulation, loss of mitochondrial transmembrane potential, release of cytochrome c, and activation of caspase-3 (Herrera et al., FASEB J 2001;15:741-751). In this work, we have analyzed how TGF-beta1 activates the caspase cascade and whether or not caspase activation precedes the oxidative stress induced by this factor. Our results show that TGF-beta1 activates at least caspase-3, -8, and -9 in rat fetal hepatocytes, which are not required for ROS production, glutathione depletion, bcl-xL down-regulation, and initial cytochrome c release. However, caspase activation mediates cleavage of Bid and Bcl-xL that could originate an amplification loop on the mitochondrial events. An interesting result is that transmembrane potential disruption occurs later than the initial cytochrome c release and is mostly blocked by the pan-caspase inhibitor Z-VAD.fmk, indicating that the decrease in mitochondrial transmembrane potential (Delta(Psi)m) may be a consequence of caspase activity rather than the mechanism by which TGF-beta induces cytochrome c efflux. Finally, although Z-VAD.fmk completely blocks nucleosomal DNA fragmentation, it only delays cell death, which suggests that activation of the apoptotic program by TGF-beta in fetal hepatocytes inevitably leads to death, with or without caspases.

Activation of p38MAPK by TGF-beta in fetal rat hepatocytes requires radical oxygen production, but is dispensable for cell death.

We have previously found that transforming growth factor-beta (TGF-beta) induces an increase in radical oxygen species (ROS) production that mediates its apoptotic effects in fetal hepatocytes. In this paper we show that TGF-beta activates p38 mitogen-activated protein kinase (p38MAPK) and ROS may be responsible for this activation. Activation of p38MAPK occurs late, coincident with the maximal production of ROS, it is inhibited by radical scavengers and it is accentuated by the presence of glutathione synthesis inhibitors. However, p38MAPK does not appear to be involved in any of the apoptotic events: loss of Bcl-x(L) levels, cytochrome c release, cleavage of caspase substrates and loss of cell viability.

TNF-alpha inhibits UCP-1 expression in brown adipocytes via ERKs. Opposite effect of p38MAPK.

Tumor necrosis factor-alpha (TNF-alpha) activates extracellular-regulated kinases (ERKs) and p38 mitogen-activated protein kinase (p38MAPK), and inhibits the expression of uncoupling protein-1 (UCP-1) and adipocyte-specific genes in rat fetal brown adipocytes. MEK inhibition with PD98059 abolished the inhibitory effect of TNF-alpha on UCP-1, but not on adipogenic genes. In contrast, inhibition of p38MAPK with SB203580 potentiated the negative effect of TNF-alpha on UCP-1 and adipogenic genes. The inhibitory action of TNF-alpha was partially correlated with changes in C/EBPalpha and beta protein levels and in their DNA binding activity, suggesting a role for these transcription factors. However, other transcription factors might explain the different regulation of UCP-1 and adipogenic genes by ERKs.

Reactive oxygen species (ROS) mediates the mitochondrial-dependent apoptosis induced by transforming growth factor (beta) in fetal hepatocytes.

Treatment of fetal rat hepatocytes with transforming growth factor beta (TGF-beta) is followed by apoptotic cell death. Analysis of radical oxygen species (ROS) content and mitochondrial transmembrane potential (Deltapsim), using specific fluorescent probes in FACScan and confocal microscopy, showed that TGF-beta mediates ROS production that precedes the loss of Deltapsim, the release of cytochrome c, and the activation of caspase 3. TGF-beta induces a decrease in the protein and mRNA levels of bcl-xL, an antiapoptotic member of the Bcl-2 family. In contrast, there is no change in the expression and/or translocation of Bax, a proapoptotic member of the same family. EGF maintains Bcl-xL, preventing Deltapsim collapse and release of cytochrome c. The presence of radical scavengers blocks the decrease in bcl-xL levels, Deltapsim collapse, cytochrome c release, and activation of caspase 3; in contrast, the presence of glutathione synthesis inhibitors such as BSO accentuated the effect. The incubation of fetal hepatocytes in the presence of ter-butyl-hydroperoxide alone produces a decrease in bcl-xL. These results indicate that during the apoptosis mediated by TGF-beta in fetal hepatocytes, ROS may be responsible for the decrease in bcl-xL mRNA levels that precedes the loss of Deltapsim, the release of cytochrome c, and the activation of caspase 3, culminating in cell death.

p38 mitogen-activated protein kinase mediates tumor necrosis factor-alpha-induced apoptosis in rat fetal brown adipocytes.

Tumor necrosis factor-alpha (TNFalpha) induces apoptosis and cell growth inhibition in primary rat fetal brown adipocytes. Here, we examine the role played by some members of the mitogen-activated protein kinase (MAPK) superfamily. TNFalpha activates extracellular regulated kinase-1/2 (ERK1/2) and p38MAPK. Inhibition of p38MAPK by either SB203580 or SB202190 highly reduces apoptosis induced by TNFalpha, whereas ERK inhibition potentiates it. Moreover, cotransfection of an active MKK3 mutant and p38MAPK induces apoptosis. p38MAPK inhibition also prevents TNFalpha-induced cell cycle arrest, whereas MEK1 inhibition enhances this effect, which correlates with changes in proliferating cell nuclear antigen expression, but not in cyclin D1. c-Jun and activating transcription factor-1 are potential downstream effectors of p38MAPK and ERKs upon TNFalpha treatment. Thus, TNFalpha-induced c-Jun messenger RNA expression requires ERKs activation, whereas p38MAPK inhibition enhances its expression. In addition, TNFalpha-induced activating transcription factor-1 phosphorylation is extensively decreased by SB203580. However, TNFalpha-induced NF-kappaB DNA-binding activity is independent of p38MAPK and ERK activation. On the other hand, C/EBP homology protein does not appear to mediate the actions of TNFalpha, because its expression is almost undetectable and even reduced by TNFalpha. Finally, although TNFalpha induces c-Jun N-terminal kinase (JNK) activation, transfection of a dominant negative of either JNK1 or JNK2 had no effect on TNFalpha-induced apoptosis. These results suggest that p38MAPK mediates TNFalpha-induced apoptosis and cell cycle arrest, whereas ERKs do the opposite, and JNKs play no role in this process of apoptosis.

Noradrenaline induces brown adipocytes cell growth via beta-receptors by a mechanism dependent on ERKs but independent of cAMP and PKA.

It has been well established that the key role of noradrenaline is the induction of uncoupling-protein-1 (UCP-1) expression, the unique marker of brown adipocytes. However, its implication on proliferation and the pathways involved are not as well characterized. By using rat fetal brown adipocytes as a model, we show that, although noradrenaline activates extracellular regulated kinases (ERKs) through beta-, alpha1-, and alpha2-receptors, only beta-receptors mediate cell growth by a mechanism that requires ERKs activation but is independent of cyclic-adenosine-monophosphate/protein kinase A (cAMP/PKA). Conversely, the cAMP/PKA cascade mediates noradrenaline-induced UCP-1 expression, whereas ERKs pathway attenuates thermogenic differentiation. On the other hand, alpha1- and alpha2-receptors have an antiproliferative effect that is enhanced by ERK inhibition.

Epidermal growth factor impairs the cytochrome C/caspase-3 apoptotic pathway induced by transforming growth factor beta in rat fetal hepatocytes via a phosphoinositide 3-kinase-dependent pathway.

Transforming growth factor beta (TGF-beta)-mediated apoptosis is one of the major death processes in the liver. We have previously shown that epidermal growth factor (EGF) is an important survival signal for TGF-beta-induced apoptosis in fetal hepatocytes (Fabregat et al., FEBS Lett 1996;384:14-18). In this work we have studied the intracellular signaling implicated in the protective effect of EGF. We show here that EGF activates p42 and p44 mitogen-activated protein kinases (MAPK). However, mitogen extracellular kinase (MEK) inhibitors do not block the survival effect of EGF. EGF also activates phosphoinositide 3-kinase (PI 3-kinase) and protein kinase B (PKB/AKT) in these cells. The presence of PI 3-kinase inhibitors blocks the protective effect of EGF on cell viability, DNA fragmentation, and caspase-3 activity. We have found that TGF-beta disrupts the mitochondrial transmembrane potential (DeltaPsi(m))( )and activates the release of cytochrome c, this effect being blocked by EGF, via a PI 3-kinase-dependent pathway. A detailed study on bcl-2 superfamily gene expression shows that TGF-beta produces a decrease in the messenger RNA (mRNA) and protein levels of bcl-x(L), an antiapoptotic member of this family, capable of preventing cytochrome c release. EGF is able to maintain bcl-x(L) levels even in the presence of TGF-beta. PI 3-kinase inhibitors completely block the protective effect of EGF on TGF-beta-induced bcl-x(L )down-regulation. We conclude that PI 3-kinase mediates the survival effect of EGF on TGF-beta-induced death by acting upstream from the mitochondrial changes, i.e., preventing bcl-x(L) down-regulation, cytochrome c release, and activation of caspase-3.

Apoptotic response to TGF-beta in fetal hepatocytes depends upon their state of differentiation.

Transforming growth factor-beta (TGF-beta1) induces death of fetal hepatocytes by an apoptotic mechanism. However, even when very high concentrations and/or long-term exposure to the cytokine is used, 40-50% of cells always survive. The process of cell survival is coincident with changes in morphology and phenotype, with cells showing a fibroblastic appearance and eliciting an epithelial-fibroblastic transition. Surviving cells continue responding to TGF-beta in terms of growth control. Expression of liver-specific genes is very low in these cells; this effect is due to the decrease in their rate of transcription as soon as 2 h after the addition of the factor. Surviving cells present a decreased DNA binding activity for liver-enriched transcription factors, an increased DNA binding activity for AP-1, and a high expression of protooncogenes. These cells are immature hepatocytes since in the presence of the appropriate signal (i.e., epidermal growth factor), they can differentiate, organizing in cell clusters and increasing both liver-specific mRNA expression and liver-enriched transcription factor activity. In accord with these results, TGF-beta, secreted at high concentrations during liver carcinogenesis, might induce death of normal cells while providing a selective advantage for the survival of cells that are "partially transformed" or "less differentiated" and unresponsive to the factor.

Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae CHS7 gene encodes an integral membrane protein located in the ER which is directly involved in chitin synthesis through the regulation of chitin synthase III (CSIII) activity. In the absence of CHS7 product, Chs3p, but not other secreted proteins, is retained in the ER, leading to a severe defect in CSIII activity and consequently, to a reduced rate of chitin synthesis. In addition, chs7 null mutants show the yeast phenotypes associated with a lack of chitin: reduced mating efficiency and lack of the chitosan ascospore layer, clear indications of Chs7p function throughout the S. cerevisiae biological cycle. CHS3 overexpression does not lead to increased levels of CSIII because the Chs3p excess is retained in the ER. However, joint overexpression of CHS3 and CHS7 increases the export of Chs3p from the ER and this is accompanied by a concomitant increase in CSIII activity, indicating that the amount of Chs7p is a limiting factor for CSIII activity. Accordingly, CHS7 transcription is increased when elevated amounts of chitin synthesis are detected. These results show that Chs7p forms part of a new mechanism specifically involved in Chs3p export from the ER and consequently, in the regulation of CSIII activity.

Glucocorticoid receptor down-regulates c-Jun amino terminal kinases induced by tumor necrosis factor alpha in fetal rat hepatocyte primary cultures.

The effect of dexamethasone on Jun N-terminal kinase (JNK) activity was assayed by using fetal hepatocytes in primary culture. The addition of tumor necrosis factor alpha (TNF-alpha) caused an increase in JNK in a dose- and time-dependent manner. We show that activation of JNK by this extracellular signal is inhibited by dexamethasone in a dose-dependent fashion. This inhibitory effect was observed in cells treated for 10 minutes with dexamethasone in the presence of protein phosphatase inhibitors such as orthovanadate or okadaic acid, or in cells previously treated with actinomycin D. Glucocorticoid receptor (GR) can be precipitated with the fusion protein, GST-c-Jun (1-79), bound to agarose beads. However, the inhibitory effect of glucocorticoids on JNK activity was also observed using ATF-2 as substrate. In addition, dexamethasone inhibits JNK phosphorylation induced by TNF-alpha. Finally, we show that GR can also be phosphorylated in tyrosine residues in response to TNF-alpha and epidermal growth factor (EGF) upon ligand-binding. Our results suggest that the anti-inflammatory effect of glucocorticoids on the inflammatory pathways induced by TNF-alpha can be explained, at least in part, by modulating JNK activity through a direct protein-protein interaction; the JNK phosphorylation and tyrosine-phosphorylation state of GR may be regulatory steps also involved in that effect.

Phorbol esters down-regulate alpha-fetoprotein gene expression without affecting growth in fetal hepatocytes in primary culture.

The effects of phorbol esters (phorbol-12,13-dibutyrate, PDB) on alpha-fetoprotein expression and cell growth were assayed by using fetal hepatocytes in primary culture. PDB acts synergistically with epidermal growth factor (EGF) to specifically decrease alpha-fetoprotein (AFP) mRNA levels, without affecting the expression of other genes of the same family, such as albumin and Vitamin D-binding protein (DBP). This effect is PDB-dose dependent, maximal effects being at 10 ng/ml. The implication of protein kinase C (PKC) in this effect seems clear since bisindolylmaleimide (BIS), a specific PKC inhibitor, completely blocks the PDB effect on AFP expression. Nuclear run-on experiments show that the decrease in AFP mRNA levels is mainly due to an inhibition in the transcription rate of the gene. Determination of PKC activities shows that fetal hepatocytes contain mainly Ca(2+)-independent isoenzymes, which patterns of activation was not modified by EGF plus PDB treatment with respect to PDB treatment. We have found that MAPK and JNK activities, c-jun and c-fos mRNA levels and AP-1 binding activity are notably increased when cells are incubated with both EGF and PDB, PDB does not stimulate growth of fetal hepatocytes, measured either as [3H]-thymidine incorporation into DNA or by cell cycle analysis using flow cytometry. All these results suggest that activation of PKC may affect liver gene expression rather than cell growth in fetal hepatocytes.

Regulation of gene expression by interleukin-6 in fetal rat hepatocyte primary cultures: role of epidermal growth factor and dexamethasone.

Fetal rat hepatocytes incubated in the absence of hormonal signals, or under proliferative (presence of epidermal growth factor [EGF]) or differentiative (presence of dexamethasone) culture conditions, showed responsiveness to interleukin-6 (IL-6). Northern blotting analysis for some typical acute phase genes such as haptoglobin and other proteins not previously identified as acute-phase reactants, such as alpha-fetoprotein, beta 2-microglobulin, and fibronectin, showed a positive modulation by IL-6, in a dose-dependent manner. However, a well-characterized negative acute-phase reactant such as albumin was not responsive to IL-6. The well-established synergism between glucocorticoids and IL-6 on inducing transcription is absent in fetal hepatocytes. Conversely, the combination of IL-6 and EGF produced different patterns of expression, depending on the messenger RNA (mRNA) analyzed. Thus, EGF abolished the increased mRNA levels of haptoglobin caused by IL-6 but had no effect on other genes such as alpha-fetoprotein and fibronectin.

[Incidence of malignancy in millimetric polyps]. / Incidencia de malignidad en los pólipos milimétricos.

This paper is based on the analysis of 178 polyps of 5 mm or less (polyps we have termed "millimetric") studied in the Endoscopy Department of "La Paz" Hospital, Madrid, during 1993. All polyps fulfilling these characteristics detected during this period are included. The 178 polyps represent 43.4% of all polyps (N = 410) found on colonoscopy in this department in this period. The variables considered in the study protocol include age, sex, localization, morphology and histological examination, with particular attention to high risk histological lesions such as signs of possible malignancy.; we also performed a comparative study between the results obtained from the 178 millimetric polyps (Group I) and the 232 polyps greater than 5 mm (Group II) obtained during the same period. The endoscopic technique for the resection of the polyps was evaluated together with its possible complications. Although there were no significant differences found in respect to age, sex and location, there were morphological differences with a greater number of pediculated or semi-pediculated polyps in Group I whilst there were more sessile polyps in Group II. Adenomatous polyps were the most frequent (84%) in both groups. There was a greater incidence of signs of possible early malignant changes in Group II polyps (10) than in Group I (3.3%). The conclusions which may be drawn from our study are that it is clinically advisable to excise all polyps of 5 mm or less as the frequency of high risk histological changes is not negligible (3.3%), and excision is not problematic as the technique is easy and there have been no complications in our series.

Neoadjuvant cisplatin chemotherapy before radical cystectomy in invasive transitional cell carcinoma of the bladder: a prospective randomized phase III study.

From November 1984 to April 1989, 122 patients with clinical T2-4a Nx-2 M0 transitional cell carcinoma of the bladder were entered in a prospective randomized trial to compare survival between a control group of 60 patients treated only with radical cystectomy (arm A) and a group of 62 patients treated with 3 cycles of 100 mg./m.2 neoadjuvant cisplatin before radical cystectomy (arm B). Secondary objectives of the trial were comparison of the disease-free interval and time to death, significance of response of the primary tumor to cisplatin, pattern of relapse and toxicity. As of April 1993 after a median followup of 78.2 months (range 48 to 101) no difference in survival between the control patients and those who received neoadjuvant cisplatin has been observed. The overall direct survival is 37.3% for arm A and 35.5% for arm B. The survival rate of the 109 patients who complied with the protocol is 38.2% for 55 patients of the control group and 40.7% for 54 patients of the cisplatin group. Survival rates of patients theoretically rendered free of disease by radical cystectomy (complete response pT0-4a, pN0-2, M0) is 43.7% for 40 control patients and 47.8% for 41 cisplatin treated patients. The time to relapse in complete response patients was significantly longer (p = 0.0298) for those who received cisplatin (arm A 13.1 months versus arm B 30.3 months). The time to death (cause specific) did not differ significantly between both groups overall (p = 0.1349) but it was significantly different between controls and responders (p = 0.0501). Preoperative cisplatin downstaged the primary tumor in 19 patients (33.9%), of whom 11 (19.6%) had no tumor in the cystectomy specimen (pT0) and 8 (14.3%) had superficial tumor (pTis pTa pT1). In 6 patients (9.7%) disease progressed during chemotherapy. The survival of the responders was significantly better than that of nonresponders (p = 0.0142), with specific death rate of 26.3% and 62.5%, respectively, and a median time to death of 43 months for responders and 30.5 months for nonresponders. Patients without nodal involvement (pN0) or with only 1 micrometastasis (pN1) fared significantly better (p = 0.0001) than those with major node invasion (pN2-4), irrespective of the treatment received. The survival rate is 48.6% for patients with pN0 disease, 37.5% for pN1 and 5% for pN2-4. Toxicity of cisplatin was minimal and there were no differences in perioperative morbidity between the arms.(ABSTRACT TRUNCATED AT 400 WORDS)

Noradrenergic modulation of albumin expression in growth-stimulated adult rat hepatocytes in primary culture.

Serum albumin is the most abundant protein synthesized by liver cells, and its production is a reliable indicator of the differentiated state of hepatocytes. We have recently shown that fetal rat hepatocytes cultured under proliferative conditions, i.e., in the presence of EGF, responded to glucagon and noradrenaline increasing albumin protein and mRNA levels (de Juan et al., 1992. J. Cell. Physiol., 152:95-101). This effect was mimicked by agents that increase cyclic AMP levels. In this report, we show that in regenerating liver, noradrenaline modulation of albumin expression seems to be different. Hepatocytes from hepatectomized rats were cultured at low cell density and in the presence of EGF. Under these conditions, noradrenaline, which acted synergistically with EGF increasing DNA synthesis (de Juan et al., 1992. Exp. Cell. Res., 202:495-500), produced a decrease in albumin mRNA levels. This effect was dose-dependent, being maximum at 1 microM noradrenaline. Noradrenergic effect seemed to be mediated by alpha 1-receptors, because it was blocked by prazosin, but not by propranolol. Other Ca(2+)-increasing agents, as vasopressin, angiotensin II, or ATP, did not produce any effect. However, albumin mRNA levels decreased when the cells were incubated in the presence of tetradecanoyl phorbol-13-acetate (TPA). In addition, noradrenergic modulation of albumin expression was blocked by staurosporine, a protein kinase inhibitor with relative specificity for protein kinase C. Thus we can conclude that the role of noradrenaline on the regulation of liver growth and differentiation changes from fetal to adult life. This change is probably due to its action on different receptors: beta-receptors in fetal hepatocytes and alpha 1-receptors in the adult liver.