scholarly journals Differential expression and regulation of nucleoside transport systems in rat liver parenchymal and hepatoma cells

Hepatology ◽  
1998 ◽  
Vol 28 (6) ◽  
pp. 1504-1511 ◽  
Author(s):  
Belén del Santo ◽  
Raquel Valdés ◽  
João Mata ◽  
Antonio Felipe ◽  
F. Javier Casado ◽  
...  
Keyword(s):  
Differential Expression ◽  
Rat Liver ◽  
Hepatoma Cells ◽  
Nucleoside Transport ◽  
Transport Systems ◽  
Liver Parenchymal

scholarly journals Nucleoside uptake in rat liver parenchymal cells

1996 ◽  
Vol 317 (3) ◽  
pp. 835-842 ◽  
Author(s):  
Joan MERCADER ◽  
Mireia GOMEZ-ANGELATS ◽  
Belén del SANTO ◽  
Javier CASADO ◽  
Antonio F. FELIPE ◽  
...  
Keyword(s):  
Rat Liver ◽  
Nucleoside Transport ◽  
Transport Systems ◽  
Dependent Manner ◽  
Transport Activity ◽  
Liver Parenchymal ◽  
Uridine Uptake ◽  
High Concentrations ◽  
Parenchymal Cells ◽  
Dose Dependent

Rat liver parenchymal cells express Na+-dependent and Na+-independent nucleoside transport activity. The Na+-dependent component shows kinetic properties and substrate specificity similar to those reported for plasma membrane vesicles [Ruiz-Montasell, Casado, Felipe and Pastor-Anglada (1992) J. Membr. Biol. 128, 227–233]. This transport activity shows apparent Km values for uridine in the range 8–13 μM and a Vmax of 246 pmol of uridine per 3 min per 106 cells. Most nucleosides, including the analogue formycin B, cis-inhibit Na+-dependent uridine transport, although thymidine and cytidine are poor inhibitors. Inosine and adenosine inhibit Na+-dependent uridine uptake in a dose-dependent manner, reaching total inhibition. Guanosine also inhibits Na+-dependent uridine uptake, although there is some residual transport activity (35% of the control values) that is resistant to high concentrations of guanosine but may be inhibited by low concentrations of adenosine. The transport activity that is inhibited by high concentrations of thymidine is similar to the guanosine-resistant fraction. These observations are consistent with the presence of at least two Na+-dependent transport systems. Na+-dependent uridine uptake is sensitive to N-ethylmaleimide treatment, but Na+-independent transport is not. Nitrobenzylthioinosine (NBTI) stimulates Na+-dependent uridine uptake. The NBTI effect involves a change in Vmax, it is rapid, dose-dependent, does not need preincubation and can be abolished by depleting the Na+ transmembrane electrochemical gradient. Na+-independent uridine transport seems to be insensitive to NBTI. Under the same experimental conditions, NBTI effectively blocks most of the Na+-independent uridine uptake in hepatoma cells. Thus the stimulatory effect of NBTI on the concentrative nucleoside transporter of liver parenchymal cells cannot be explained by inhibition of nucleoside efflux.

Nucleoside transporters and liver cell growth

1998 ◽  
Vol 76 (5) ◽  
pp. 771-777 ◽  
Author(s):  
Marçal Pastor-Anglada ◽  
Antonio Felipe ◽  
F Javier Casado ◽  
Belén Del Santo ◽  
João F Mata ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Growth ◽  
Liver Cell ◽  
Nucleoside Transporters ◽  
Nucleoside Transport ◽  
Transport Systems ◽  
Liver Growth ◽  
Liver Parenchymal ◽  
Hepatocyte Regeneration ◽  
Parenchymal Cells

Liver parenchymal cells show a wide variety of plasma membrane transporters that are tightly regulated by endocrine and nutritional factors. This review summarizes work performed in our laboratory on these transport systems, particularly nucleoside transporters, which are up-regulated in physiological situations associated with liver cell growth. Rat hepatocytes show a Na+-dependent nucleoside transport activity that is stimulated by pancreatic hormones. Indeed, this biological activity appears to be the result of the co-expression of at least two isoforms of nucleoside carriers, CNT1 and CNT2 (also called SPNT). These two transporters are up-regulated during the early phase of liver growth after partial hepatectomy, although to different extents, suggesting differential regulation of the two isoforms. The recent generation of isoform-specific antibodies allowed us to demonstrate that carrier expression may also have complex post-transcriptional regulation on the basis of the lack of correspondence between mRNA and protein levels. The analysis of nucleoside transport systems in hepatoma cells and the comparison with those in hepatocytes has also provided evidence that the differentiation status of liver parenchymal cells may determine the pattern of nucleoside transporters expressed.Key words: liver, hepatocyte, regeneration, cell cycle, nucleoside, plasma membrane, transport systems.

scholarly journals Induction of amino acid transport in primary cultures of adult rat liver parenchymal cells by insulin.

1976 ◽  
Vol 251 (10) ◽  
pp. 3014-3020 ◽  
Author(s):  
R F Kletzien ◽  
M W Pariza ◽  
J E Becker ◽  
V R Potter ◽  
F R Butcher
Keyword(s):  
Amino Acid ◽  
Rat Liver ◽  
Amino Acid Transport ◽  
Primary Cultures ◽  
Acid Transport ◽  
Liver Parenchymal ◽  
Adult Rat ◽  
Parenchymal Cells
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