scholarly journals l-alanine uptake by rat liver parenchymal and haematopoietic cells during the perinatal period

1993 ◽  
Vol 293 (3) ◽  
pp. 819-824 ◽  
Author(s):  
J V Martinez-Mas ◽  
J Casado ◽  
A Felipe ◽  
J J G Marin ◽  
M Pastor-Anglada
Keyword(s):  
Perinatal Period ◽  
Neonatal Rat ◽  
Transport Systems ◽  
Fetal Life ◽  
Adult Rats ◽  
Liver Parenchymal ◽  
Adult Rat ◽  
Haematopoietic Cells ◽  
Parenchymal Cells ◽  
Rat Livers

Alanine disposal by liver parenchymal and haematopoietic cells from 21-day fetuses, newborns and adult rats was studied. Preparations selectively enriched in either haematopoietic cells or hepatocytes were obtained by direct perfusion of fetal- and neonatal-rat livers. L-Alanine transport into liver parenchymal cells was best fitted to two Na(+)-dependent saturable systems. The high-affinity system showed a much higher activity (Vmax.) in hepatocytes from fetuses and newborns than in those from adult rats (2.4, 4.3 and 0.3 nmol/8 min per 10(6) cells for fetuses, newborns and adults respectively). Vmax. for the low-affinity component was slightly lower during the perinatal period than in the adult (about 30 nmol/8 min per 10(6) cells for hepatocytes from fetuses and newborns, versus 48 nmol/8 min per 10(6) cells for adult rat parenchymal cells). Haematopoietic cells from fetal-rat livers showed significant Na(+)-dependent L-alanine uptake which was completely abolished after birth. These results show that the transport systems involved in L-alanine uptake by liver parenchymal cells are fully developed before birth. This probably contributes to fulfilling the high requirement for neutral amino acids for protein synthesis during development. Haematopoietic cells may play an important role in liver amino acid metabolism during fetal life.

CARTILAGE RESPONSE TO PLASMA AND PLASMA SOMATOMEDIN ACTIVITY IN RATS RELATED TO GROWTH BEFORE AND AFTER BIRTH

1981 ◽  
Vol 90 (1) ◽  
pp. 133-142 ◽  
Author(s):  
D. J. HILL ◽  
S. J. ANDREWS ◽  
R. D. G. MILNER
Keyword(s):  
Body Weight ◽  
Costal Cartilage ◽  
Basal Medium ◽  
Tail Length ◽  
Rat Plasma ◽  
Neonatal Rat ◽  
Postnatal Life ◽  
Fetal Life ◽  
Adult Rats ◽  
Adult Rat

Cartilage response to plasma, plasma somatomedin activity, body weight and length were measured in rats from 15 days of fetal age to 37 days postnatally. The metabolic activity of costal cartilage was assessed by the incorporation of [35S]sulphate in basal medium and after stimulation by plasma. It was found that (a) A significant stimulation of isotope uptake above basal levels occurred in the presence of 15% standard adult rat plasma at every age studied. (b) The degree of stimulation, a measure of cartilage sensitivity to plasma growth factors, increased through the latter part of fetal life but fell after birth. A high degree of cartilage stimulation was seen on day 6 of postnatal life. (c) The changes in cartilage sensitivity and in the stimulated isotope uptake, resembled the changes observed in growth rate for body weight, nose–rump length and tail length. (d) Plasma somatomedin activity measured by the pig costal cartilage assay was low in the fetus and neonate but rose to adult values 9 days after birth. However, plasma from fetal or neonatal rats tested on cartilage from rats of the same age was equipotent to adult rat plasma. (e) Plasma from hypophysectomized adult rats had a low potency in stimulating isotope uptake by neonatal rat cartilage but was equipotent to normal adult rat plasma in its action on fetal cartilage. (f) The action of plasma from hypophysectomized rats on fetal cartilage was unaffected by dialysis but was destroyed by incubation with trypsin.

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

Effect of dexamethasone on the isozyme pattern of adult rat liver parenchymal cells in primary cultures

1982 ◽  
Vol 45 (2) ◽  
Author(s):  
JuanEmilio Fel�u ◽  
Julio Coloma ◽  
Mar�a-Jos� G�mez-Lech�n ◽  
Mar�aDolores Garc�a ◽  
Jos� B�guena
Keyword(s):  
Rat Liver ◽  
Primary Cultures ◽  
Isozyme Pattern ◽  
Liver Parenchymal ◽  
Adult Rat ◽  
Parenchymal Cells

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.

scholarly journals Regulation of coenzyme A biosynthesis by glucagon and glucocorticoid in adult rat liver parenchymal cells

1980 ◽  
Vol 188 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Colleen M. Smith ◽  
C. Richard Savage
Keyword(s):  
Cyclic Amp ◽  
Rat Liver ◽  
Maximum Effect ◽  
Maximal Effect ◽  
Dibutyryl Cyclic Amp ◽  
Liver Parenchymal ◽  
Adult Rat ◽  
Intracellular Mechanism ◽  
Inhibitor Of Protein Synthesis ◽  
Parenchymal Cells

We studied the effects of glucagon, dibutyryl cyclic AMP and dexamethasone on the rate of [14C]pantothenate conversion to CoA in adult rat liver parenchymal cells in primary culture. The presence of 30nm-glucagon increased the rate by about 1.5-fold relative to control cultures (range 1.4–2.3) and 2.4-fold relative to cultures containing 1–3m-i.u. of insulin/ml. The half-maximal effect was obtained at 3nm-glucagon. Dibutyryl cyclic AMP plus theophylline also enhanced the rate by about 1.5-fold. Dexamethasone acted synergistically with glucagon; glucagon at 0.3nm had no effect when added alone, but resulted in a 1.7-fold enhancement when added in the presence of dexamethasone (maximum effect at 50nm). The 1.4-fold enhancement caused by the addition of saturating glucagon concentrations was increased to a 3-fold overall enhancement by the addition of dexamethasone. However, dexamethasone added alone over the range 5nm to 5μm had no effect on the rate of [14C]pantothenate conversion to CoA. The stimulatory effect of dibutyryl cyclic AMP plus theophylline was also enhanced by the addition of dexamethasone. Changes in intracellular pantothenate concentration or radioactivity could not account for the stimulatory effects of glucagon, dibutyryl cyclic AMP or dexamethasone. Addition of 18μm-cycloheximide, an inhibitor of protein synthesis, decreased the rate of incorporation of [14C]pantothenate into CoA and the enhancement of this rate by glucagon and dibutyryl cyclic AMP plus theophylline in a reversible manner. These results demonstrate an influence of glucagon, dibutyryl cyclic AMP and glucocorticoids on the intracellular mechanism regulating total CoA concentrations in the liver.

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.

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