Temperature-dependent changes in activation energies of the transport systems for nucleosides, choline and deoxyglucose of cultured Novikoff rat hepatoma cells and effects of cytochalasin B and lipid solvents

1975 ◽  
Vol 25 (1) ◽  
pp. 381-396 ◽  
Author(s):  
Peter G. W. Plagemann ◽  
John Erbe
Keyword(s):  
Cytochalasin B ◽  
Hepatoma Cells ◽  
Activation Energies ◽  
Transport Systems ◽  
Temperature Dependent ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

scholarly journals Cell cycle and growth stage-dependent changes in the transport of nucleosides, hypoxanthine, choline, and deoxyglucose in cultured Novikoff rat hepatoma cells.

1975 ◽  
Vol 64 (1) ◽  
pp. 29-41 ◽  
Author(s):  
P G Plagemenn ◽  
D P Richey ◽  
J M Zylka ◽  
J Erbe
Keyword(s):  
Cell Cycle ◽  
De Novo ◽  
Hepatoma Cells ◽  
S Phase ◽  
Transport Processes ◽  
Transport Systems ◽  
Thymidine Transport ◽  
Inhibition Of Dna Synthesis ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

Populations of Novikoff rat hepatoma cells (subline N1S1-67) were monitored for the rates of transport of various substrates and for their incorporation into acid-insoluble material as a function of the age of cultures of randomly growing cells in suspension as well as during traverse of the cells through the cell cycle. Populations of cells were synchronized by a double hydroxyurea block or by successive treatment with hydroxyurea and Colcemid. Kinetic analyses showed that changes in transport rates related to the age of cultures or the cell cycle stage reflecte alterations in the V max of the transport processes, whereas the Km remained constant, indicating that changes in transport rates reflect alterations in the number of functional transport sites. The transport sites for uridine and 2-deoxy-D-glucose increased continuously during traverse of the cells through the cell cycle, whereas those for choline and hypoxanthine were formed early in the cell cycle. Increases in thymidine transport sites were confined to the S phase. Synchronized cells deprived of serum failed to exhibit normal increases in transport sites, although the cells divided normally at the end of the cell cycle. Arrest of the cells in mitosis by treatment with Colcemid prevented any further increases in transport rates. The formation of functional transport sites was also dependent on de novo synthesis of RNA and protein. Inhibition of DNA synthesis in early S phase inhibited the increase in thymidine transport rates which normally occurs during the S phase, but had no effect on the formation of the other transport systems. Transport rates also fluctuated markedly with the age of the cultures of randomly growing cells, reaching maximum levels in the mid-exponential phase of growth. The transport systems for thymidine and uridine were rapidly lost upon inhibition of protein and RNA synthesis, and thus seem to be metabolically unstable, whereas the transport systems for choline and 2-deoxy-D-glucose were stable under the same conditions.

scholarly journals Rat hepatoma cells express novel transport systems for glutamine and glutamate in addition to those present in normal rat hepatocytes

1998 ◽  
Vol 330 (1) ◽  
pp. 255-260 ◽  
Author(s):  
D. John MGIVAN
Keyword(s):  
Cell Line ◽  
Transport System ◽  
Hepatoma Cell ◽  
Rat Hepatocytes ◽  
Hepatoma Cells ◽  
Transport Systems ◽  
Hepatoma Cell Line ◽  
High Affinity ◽  
Rat Hepatoma ◽  
Rat Hepatoma Cells

The rat hepatoma cell line H4-II-E was found to express much higher activities of Na+-dependent glutamine and aspartate transport than those observed in normal cultured hepatocytes, in agreement with previous work of others on human hepatocytes. Na+-dependent glutamine transport in rat hepatoma cells could be resolved into two components. One was pH-dependent, tolerated Li+ for Na+ substitution and was inhibited only by asparagine and histidine; characteristics similar to those of transport System N in hepatocytes. The other transport system had a similar Km for glutamine but was pH independent, did not accept Li+ ions and was completely inhibited by excess concentrations of lysine, histidine, leucine, serine and cysteine, but not by methyl-aminoisobutyrate or phenylalanine. This pattern of inhibition is distinct from that of any transporter occurring in normal hepatocytes and may indicate the presence of a new transporter isoform. Similar results were obtained with the cell line HTC. Na+-dependent aspartate transport in H4 hepatoma cells was mediated by a high-affinity system (Km 5 μM) and was inhibited by D-aspartate and L-glutamate but not by D-glutamate - properties characteristic of the high-affinity glutamate transporter EAAC1. C-terminal antibodies to the EAAC1 protein recognized a single band of 58 kDa in hepatocyte membranes, but an additional strong band of 60 kDa was present in H4 hepatoma cells. These results provide further evidence for the view that tumour cells may express additional isoforms of amino acid transport systems which are not present in non-transformed cells.

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