Regulation of albumin expression in fetal rat hepatocytes cultured under proliferative conditions: Role of epidermal growth factor and hormones (original) (raw)
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Journal of Cellular Physiology, 1994
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., 199%. Exp. Cell. Res., 202:495-500), produced a decrease in albumin mRNA levels. This effect was dose-dependent, being maximum at 1 pM noradrenaline. Noradrenergic effect seemed to be mediated by a,-receptors, because it was blocked by prazosin, but not by propranolol. Other Ca2+-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: @-receptors in fetal hepatocytes and a,-receptors in the adult liver. o 1994 Wiley-Liss, Inc.
Prostaglandins Leukotrienes and Medicine, 1984
A single exposure to a low concentration (lO'gmole/l) of exogenous arachidonic acid or of prostaglandins of A, E, and F series significantly stimulated primary neonatal rat hepatocytes to enter S phase irrespective of whether the extracellular calcium concentration was high (i.e., 1.8 mnole/l) or markedly reduced (i.e., 0 01 mnole/l). Similarly, a single treatment with an even smaller (lo-lGmole/l) dose of the known tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA), phenobarbital, and nafenopin enhanced hepatocytic DNA synthesis when the environmental calcium level was both high an low single application of a small concentration (10' mones such as epidermal ~l_l(JLl~~$~$'h~,of drugs such as rowth factor (EGF), glucagon, and insulin, and imidazo e and indomethacin only increased the hepato-9 cytic flow into DNA synthesis when the extracellular calcium was high. These findings reveal that the mechanisms of physiological or pharmacological, calcium-dependent stimulation of hepatocellular growth are likely to be different from those of pathological, calcium-independent stimulation, as the latter, but not the former, would involve prostaglandin-mediated metabolic processes.
Journal of Cellular Physiology, 1994
The cells in nearly pure (96-98%) primary cultures of hepatocytes from neonatal rat liver in high (1 .0 mM)-Ca2+, serum-free, synthetic Hi Wo, Ba, , , , medium initiated DNA synthesis and entered mitosis between 11 and 30 h after the addition of 10 ng/ml EGF. During the 10-h prereplicative period, the cultured hepatocytes, like regenerating rat liver cells, generated two large cyclic AMP transients, one peaking between 30 min and 2 h and the other around 6 h. Hepatocytes stimulated by the same concentration of EGF in low (0.02 mM)-Ca2+ medium increased cyclic AMP synthesis as much as the EGF-treated hepatocytes in high-Ca2+ medium, but they released the additional cyclic AMP into the medium and could not generate prereplicative internal cyclic AMP surges, initiate DNA replication, or enter mitosis. These results suggest that one of the ways external Ca2+ controls prereplicative development of hepatocytes is to restrain the release of cyclic AMP and thus enable the cell to accumulate enough internal cyclic AMP to stimulate events required to initiate DNA replication. Published
Prostaglandins, Leukotrienes and Medicine, 1984
A single exposure to a low concentration (lO'gmole/l) of exogenous arachidonic acid or of prostaglandins of A, E, and F series significantly stimulated primary neonatal rat hepatocytes to enter S phase irrespective of whether the extracellular calcium concentration was high (i.e., 1.8 mnole/l) or markedly reduced (i.e., 0 01 mnole/l). Similarly, a single treatment with an even smaller (lo-lGmole/l) dose of the known tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA), phenobarbital, and nafenopin enhanced hepatocytic DNA synthesis when the environmental calcium level was both high an low single application of a small concentration (10' mones such as epidermal ~l_l(JLl~~$~$'h~,of drugs such as rowth factor (EGF), glucagon, and insulin, and imidazo e and indomethacin only increased the hepato-9 cytic flow into DNA synthesis when the extracellular calcium was high. These findings reveal that the mechanisms of physiological or pharmacological, calcium-dependent stimulation of hepatocellular growth are likely to be different from those of pathological, calcium-independent stimulation, as the latter, but not the former, would involve prostaglandin-mediated metabolic processes.
The Journal of biological chemistry, 1979
The treatment of Hepa-2 cells, a permanent mouse hepatoma cell line, for 72 h with hydrocortisone (10(-6) M), N6,O2-dibutyryl cyclic AMP (10(-3) M), or 8-bromocyclic AMP (10(-3) M) results in a 2-,3- or 4-fold increase, respectively, in rates of synthesis and secretion of mouse serum albumin. Simultaneous treatment with hydrocortisone and N6,O2-dibutyryl cyclic AMP results in a 10-fold stimulation in these parameters, an effect that is significantly more than additive for the two compounds tested. The number of albumin mRNA sequences, determined by hybridization of total cell RNA to albumin complementary DNA, was increased in direct proportion to the increases in albumin synthesis in all experiments. The relative rate of albumin synthesis approaches in vivo levels in cells treated simultaneously with hydrocortisone and N6,O2-dibutyryl cyclic AMP. We propose that these factors may be necessary to maintain the maximal level of differentiated function in the continuous culture of Hepa-...
Hepatology, 1996
Human hepatocytes stimulated with human recombi-kd; -subunit, 34 kd) synthesized by nonparenchymal nant hepatocyte growth factor (h-rHGF) (10 ng/mL) disliver cells and other extrahepatic cells of mesodermal played a characteristic lag period before entering into origin. 1,2 Increased expression of messenger RNA the S phase. The duration of this delay was dependent (mRNA) for h-rHGF has been reported in the course of on the timing of h-rHGF addition to cultures. The highliver regeneration and inflammation, 3 and the blood est peak of DNA synthesis was observed at 120 hours of levels of this factor increased rapidly after partial hepaculture when hepatocytes were stimulated with h-rHGF tectomy and toxic liver necrosis. 4,5 HGF is one of the at 72 hours of culture. This was accompanied by an early most potent signals to stimulate DNA synthesis in he-
Experimental Cell Research, 1977
cGMP and db-cGMP administered for 20-24 h to neonatal rat hepatocytes in primary culture stimulated their DNA synthesis and proliferation only at concentrations higher than the physiological one, whereas at concentrations equal to or lower than the physiological concentration they were ineffective or inhibitory for both activities. Induction of DNA synthesis to be effected by cGMP required 15 h of treatment, preceded, however, by inhibition of the same process between the 6th and the 14th hour of exposure. In contrast, CAMP and db-CAMP stimulated the flow of cultivated hepatocytes into the S and M stages of their mitotic cycle when administered at very wide concentration range, including the physiological for CAMP and the sub-physiological for db-CAMP. CAMP was effective after 12-14 h of treatment. Equimolar mixtures of cGMP with CAMP and of db-cGMP with db-CAMP also stimulated the proliferative activity of primary hepatocytes, but only at very low doses, which induced a first peak of DNA synthesis between the 2nd and the 6th hour of treatment and a second peak at about the 18th hour. These actions of the cyclic compounds, employed singly or in equimolar combination, were shown to be specific, since they could not be reproduced by their main metabolites. The present results strengthen the view that CAMP plays a pre-eminent role in the positive regulation of hepatocyte proliferation, Contrary to the postulate of the dualistic doctrine, cGMP by itself is not proliferogenic in the physiological range; in fact, cGMP acts as an ancillary, possibly dispensable, compound whose physiological role may be to help, in cooperation with CAMP, liver cells to cross the Gl/S boundary of their growth-division cycle.