scholarly journals REGULATION OF PHOSPHOENOLPYRUVATE CARBOXYKINASE AND TYROSINE TRANSAMINASE IN HEPATOMA CELL CULTURES

1974 ◽  
Vol 60 (1) ◽  
pp. 181-191 ◽  
Author(s):  
Han van Rijn ◽  
Marinus M. Bevers ◽  
Roeland van Wijk ◽  
Wesley D. Wicks
Keyword(s):  
Growth Rate ◽  
Cyclic Amp ◽  
Dna Synthesis ◽  
Cell Cultures ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Hepatoma Cell ◽  
Transaminase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Tyrosine Transaminase ◽  
Htc Cells

The ability of N6, O2'-dibutyryl cyclic AMP (DBcAMP) to regulate a number of metabolic events in four lines of cultured rat hepatomas has been examined. Although dexamethasone induces tyrosine transaminase in all four lines, DBcAMP induces this enzyme normally only in H35 cells. A slight increase in transaminase activity was seen with MH1C1 cells and HTC cells, but no effect was detectable in RLC cells. In contrast, phosphoenolpyruvate carboxykinase activity is increased by both agents in H35 and MH1C1 cells, but neither had any effect in HTC or RLC cells. DBcAMP caused a rapid inhibition of the growth rate and DNA synthesis and an increase in protein content in both H35 and MH1C1 cells but not in HTC or RLC cells. The effect of DBcAMP on DNA synthesis in MH1C1 cells could be reversed by deoxycytidine as is also the case with H35 cells. The resistance of HTC and RLC cells to DBcAMP was not due to reduced uptake or deacylation as judged by studies with [3H]DBcAMP. The cyclic nucleotide appears to enter the cells by passive diffusion as the intracellular concentration approaches that in the medium within 30–60 min. Possible explanations for the differential responses observed are discussed.

scholarly journals Poly(adenosine diphosphate ribose) polymerase activity and nicotinamide adenine dinucleotide in differentiating cardiac muscle

1976 ◽  
Vol 154 (2) ◽  
pp. 387-393 ◽  
Author(s):  
W C. Claycomb
Keyword(s):  
Cyclic Amp ◽  
Dna Synthesis ◽  
Cardiac Muscle ◽  
Dna Polymerase ◽  
Specific Activity ◽  
Polymerase Activity ◽  
Neonatal Rat ◽  
Dibutyryl Cyclic Amp ◽  
Fresh Tissue ◽  
Dna Polymerase Α

Poly(ADP-ribose) polymerase activity in nuclei isolated from differentiating cardiac muscle of the rat has been characterized and its activity measured during development. Optimum enzyme activity is observed at pH 8.5. Poly(ADP-ribose) polymerase is inhibited by ATP, thymidine, nicotinamide, theophylline, 3-isobutyl-1-methylxanthine and caffeine and stimulated by actinomycin D. The activity measured under optimal assay conditions increases during differentiation of cardiac muscle and is inversely related to the rate of DNA synthesis and to the activities of DNA polymerase α and thymidine kinase. When DNA synthesis and the activity of DNA polymerase α are inhibited in cardiac muscle of the 1-day-old neonatal rat by dibutyryl cyclic AMP or isoproterenol, the specific activity of poly(ADP-ribose) polymerase measured in isolated nuclei is increased. The concentration of NAD+ in cardiac muscle increases during postnatal development. In the adult compared with the 1-day-old neonatal rat the concentration of NAD+ relative to fresh tissue weight, DNA or protein increased 1.7-fold, 5.2-fold or 1.4-fold respectively. The concentration of NAD+ in cardiac muscle of the 1-day-old neonatal rat can be increased by approx. 20% by dibutyryl cyclic AMP. These data suggest that NAD+ and poly(ADP-ribose) polymerase may be involved with the repression of DNA synthesis and cell proliferation in differentiating cardiac muscle.

scholarly journals Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)

1974 ◽  
Vol 142 (3) ◽  
pp. 691-693 ◽  
Author(s):  
Wieland B. Huttner ◽  
Wilhelm Krone ◽  
Hans J. Seitz ◽  
Wolfgang Tarnowski
Keyword(s):  
Cyclic Amp ◽  
Cyclic Nucleotide ◽  
Time Course ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Direct Action ◽  
Isolated Perfused Rat Liver ◽  
Dibutyryl Cyclic Amp ◽  
Low Protein ◽  
Additive Increase

Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ.

scholarly journals Dibutyryladenosine 3′:5′-cyclic monophosphate-mediated changes in rat cells involve macromolecular alterations in vinblastine-precipitable proteins

1978 ◽  
Vol 174 (3) ◽  
pp. 1071-1074
Author(s):  
A T Meza ◽  
M Rieber
Keyword(s):  
Molecular Weight ◽  
Cyclic Amp ◽  
Cell Cultures ◽  
Cyclic Nucleotide ◽  
Dibutyryl Cyclic Amp ◽  
Cyclic Monophosphate ◽  
Three Components

ts-NT3-KR rat cell cultures show the loss of three components in the molecular-weight region 200,000–250,000 when exposed to dibutyryl cyclic AMP, under conditions of both restriction and expression of the transformed phenotype. Vinblastine is able to precipitate preferentially from control cultures the species that are decreased by exposure to the cyclic nucleotide. Serum-starved cultures exposed to dibutyryl cyclic AMP reveal differences in their vinblastine precipitates, depending on whether the expression of the transformation phenotype is restricted or not.

Inhibition of Growth and DNA Synthesis in Cell Cultures by Cyclic Amp

1974 ◽  
Vol 16 (2) ◽  
pp. 301-307
Author(s):  
P. EKER
Keyword(s):  
Cyclic Amp ◽  
Dna Synthesis ◽  
Cell Cultures ◽  
Degradation Products ◽  
Liver Cells ◽  
Soluble Cell ◽  
Inhibition Of Growth ◽  
Insoluble Material ◽  
Rna And Protein Synthesis ◽  
Soluble Cell Fraction

Cyclic AMP (0.1 to 1 mM) was found to inhibit the growth of human liver cells in monolayer cultures. Significant amounts of degradation products were not detected in the medium indicating that the growth-inhibiting effect was associated with the intact cyclic nucleotide. DNA synthesis in the liver cell cultures, as measured by thymidine incorporation into acid-insoluble material, was markedly inhibited by cyclic AMP. RNA and protein synthesis were not significantly affected. Cyclic AMP induced a considerable increase in the cellular uptake of thymidine and uridine from the medium. When the liver cells were incubated in medium containing radioactive cyclic AMP, no labelled cyclic AMP could be detected in the acid-soluble cell fraction by chromatographic analysis. It is suggested that cyclic AMP does not enter the liver cells, but that its action on growth and DNA synthesis is somehow mediated through an interaction with the cell surface.

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