Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Free pyrimidine nucleotide pool of Ehrlich ascites-tumour cells. Characteristics related to quantitative studies of RNA metabolism.

ABSTRACT: Ehrlich ascites-tumour cells incubated in a mineral medium supplemented with glucose and glutamine intensely incorporated labelled uridine into free nucleotides and RNA. Detailed kinetic studies of the labelling of total acid-soluble pools of uridine and cytidine nucleotides and of RNA under standard conditions and after chase with non-radioactive uridine were carried out. The relative distribution of the radioactivity between the individual uridine phosphates as well as their total cellular contents were also determined under standard and chase conditions. The labelling kinetics of the mononucleotides and RNA by radioactive uridine and orotate were compared, and some turnover parameters were estimated by mathematical analysis of a steady-state model. The following conclusions were drawn. (1) The observed chase effect of addition of non-radioactive uridine is due to a rapid expansion of the acid-soluble uridine nucleotide pool and consequently a severalfold lowering of its specific radioactivity. (2) The free uridine nucleotides are partly separated into a large and a small compartment, labelled preferentially by exogeneous orotate and uridine respectively. (3) The half-life of the mononucleotides, at least those located in the smaller compartment, is a few minutes only, owing to a rapid exchange with the uridylic acid residues of unstable RNA species. (4) This process of reutilization of RNA-degradation products accounts for 85% (a minimum estimate) of the overall turnover of the nucleotide pool in resting cells.

SUBMITTER: Genchev DD

PROVIDER: S-EPMC1162539 | biostudies-other | 1980 Apr

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Free pyrimidine nucleotide pool of Ehrlich ascites-tumour cells. Compartmentation with respect to the synthesis of heterogeneous nuclear RNA and precursors to ribosomal RNA.

Project description:The incorporation of [14C]orotate and [14C]uridine into UMP residues of hnRNA (heterogeneous nuclear RNA) and pre-rRNA (precursors to rRNA) of Eharlich ascites-tumour cells was compared: orotate was incorporated at a markedly higher rate into hnRNA. On the other hand, the rate of incorporation of uridine into pre-rRTNA was even somewhat higher than into hnRNA. The ratio of specific radioactivities of CMP to UMP residues in pre-rRNA and hnRNA was studied. At all times of labelling this ratio was similar for both RNA species independently of the precursor used. On addition of excess unlabelled uridine, the CMP/UMP labelling ratio in both pre-rRNA and hnRNA rose. However, this increase was much more pronounced with hnRNA. It is concluded that nuclear pyrimidine nucleotide pool for RNA synthesis is compartmentalized. The synthesis of hnRNa is supplied preferentially by the large and the small compartment, respectively. A detailed model for the cellular compartmentation of uridine nucleotide precursors to RNA is proposed.U

| S-EPMC1162540 | biostudies-other

Transfer RNA and ribosomal RNA are synthesized from the same pyrimidine nucleotide pool.

Project description:We have tested the hypothesis [Wiegers, Kramer, Klapproth & Hilz (1976) Eur. J. Biochem. 64. 535-540] that the synthesis of rRNA in the nucleolus may have a partially independent supply of nucleoside triphosphates that is not completely suppressed when cells are supplied with exogenous nucleosides. For the slime mould, Physarum polycephalum, and Chinese hamster ovary cells in culture, the specific activities (3H/32P) of UMP and CMP in tRNA, which is synthesised in the nucleoplasm, and rRNA were compared after continuous labelling with [3H]uridine and [32P]phosphate. No differences were found, suggesting that transcription throughout the nucleus draws on a common supply of pyrimidine triphosphates that is uniformly labelled from exogenous [3H]uridine. As a control of the radioactive labelling schedule, a similar experiment was carried out with the prokaryote, Escherichia coli, and identical results were obtained.

| S-EPMC1153933 | biostudies-other

L-lactate transport in Ehrlich ascites-tumour cells.

Project description:Ehrlich ascites-tumour cells were investigated with regard to their stability to transport L-lactate by measuring either the distribution of [14C]lactate or concomitant H+ ion movements. The movement of lactate was dependent on the pH difference across the cell membrane and was electroneutral, as evidenced by an observed 1:1 antiport for OH- ions or 1:1 symport with H+ ions. 2. Kinetic experiments showed that lactate transport was saturable, with an apparent Km of approx. 4.68 mM and a Vmax. as high as 680 nmol/min per mg of protein at pH 6.2 and 37 degrees C. 3. Lactate transport exhibited a high temperature dependence (activation energy = 139 kJ/mol). 4. Lactate transport was inhibited competitively by (a) a variety of other substituted monocarboxylic acids (e.g. pyruvate, Ki = 6.3 mM), which were themselves transported, (b) the non-transportable analogues alpha-cyano-4-hydroxycinnamate (Ki = 0.5 mM), alpha-cyano-3-hydroxycinnamate (Ki = 2mM) and DL-p-hydroxyphenyl-lactate (Ki = 3.6 mM) and (c) the thiol-group reagent mersalyl (Ki = 125 muM). 5. Transport of simple monocarboxylic acids, including acetate and propionate, was insensitive to these inhibitors; they presumably cross the membrane by means of a different mechanism. 6. Experiments using saturating amounts of mersalyl as an "inhibitor stop" allowed measurements of the initial rates of net influx and of net efflux of [14C]lactate. Influx and efflux of lactate were judged to be symmetrical reactions in that they exhibited similar concentration dependence. 7. It is concluded that lactate transport in Ehrlich ascites-tumour cells is mediated by a carrier capable of transporting a number of other substituted monocarboxylic acids, but not unsubstituted short-chain aliphatic acids.

| S-EPMC1172721 | biostudies-other

Transport of calcium ions by Ehrlich ascites-tumour cells.

Project description:Ehrlich ascites-tumour cells accumulate Ca2+ when incubated aerobically with succinate, phosphate and rotenone, as revealed by isotopic and atomic-absorption measurements. Ca2+ does not stimulate oxygen consumption by carefully prepared Ehrlich cells, but des so when the cells are placed in a hypo-osmotic medium. Neither glutamate nor malate support Ca2+ uptake in 'intact' Ehrlich cells, nor does the endogenous NAD-linked respiration. Ca2+ uptake is completely dependent on mitochondrial energy-coupling mechansims. It was an unexpected finding that maximal Ca2+ uptake supported by succinate requires rotenone, which blocks oxidation of enogenous NAD-linked substrates. Phosphate functions as co-anion for entry of Ca2+. Ca2+ uptake is also supported by extra-cellular ATP; no other nucleoside 5'-di- or tri-phosphate was active. The accumulation of Ca2+ apparently takes place in the mitochondria, since oligomycin and atractyloside inhibit ATP-supported Ca2+ uptake. Glycolysis does not support Ca2+ uptake. Neither free mitochondria released from disrupted cells nor permeability-damaged cells capable of absorbing Trypan Blue were responsible for any large fraction of the total observed energy-coupled Ca2+ uptake. The observations reported also indicate that electron flow through energy-conserving site 1 promotes Ca2+ release from Ehrlich cells and that extra-cellular ATP increase permeability of the cell membrane, allowing both ATP and Ca2+ to enter the cells more readily.

| S-EPMC1163986 | biostudies-other

Regulation of glutathione metabolism in Ehrlich ascites tumour cells.

Project description:Glutathione metabolism was studied in cancer cells during the growth of an Ehrlich ascites tumour. GSH, but not GSSG, content decreases when cell proliferation and the rate of protein synthesis in the tumour decrease. This change correlates with a decrease in the rate of GSH synthesis and an increase in glutathione peroxidase and glutathione S-transferase activities. Glutathione efflux from tumour cells seems to co-ordinate with the rate of GSH synthesis. Cysteine, and not methionine, promotes GSH synthesis in tumour cells. However, changes in the rate of GSH synthesis are not due to limitations in the supply of blood cysteine or to changes in the intracellular amino acid pool of the cancer cells. Our data suggest that changes in protein metabolism accompanying tumour growth in vivo can modulate glutathione content in cancer cells.

| S-EPMC1133048 | biostudies-other

Some properties of adenosine kinase from Ehrlich ascites-tumour cells.

Project description:1. Adenosine kinase was measured in dialysed extracts from Ehrlich ascites-tumour cells by a chromatographic procedure. 2. In the absence of added Mg(2+) the K(m) values for ATP and adenosine were 0.22mm and 2.8mum respectively. 3. The maximum velocity of adenosine kinase with free ATP was about three times that with the Mg(2+)-ATP complex. Free Mg(2+) was a non-competitive inhibitor of the reaction. A small amount of added Mg(2+), Mn(2+) or Ca(2+) was required for maximum adenosine kinase activity after cation bound to the enzyme had been released by treatment with p-chloromercuribenzoate and then removed by dialysis. 4. GTP, ITP, deoxy-ATP, deoxy-GTP, CTP, xanthosine triphosphate, UTP and thymidine triphosphate could partially or completely replace ATP as a phosphate donor. 5. The reaction of ATP with adenosine kinase was competitively inhibited by AMP, GMP, IMP, ADP, deoxy-ADP and IDP (K(i) 0.2, 1.1, 5.9, 1.2, 0.5 and 0.78mm respectively). Enzymic activity was markedly affected by the relative concentrations of AMP, ADP and ATP in assay mixtures. 6. The results are discussed in terms of possible mechanisms regulating the rate of adenosine kinase in vivo.

| S-EPMC1198536 | biostudies-other

Host zinc metabolism and the Ehrlich ascites tumour. Zinc redistribution during tumour-related stress.

Project description:Zinc redistribution between plasma and liver has been examined in mice injected with Ehrlich-ascites-tumour cells. Within 24 h of injection plasma Zn levels decrease and Zn appears in newly synthesized liver metallothionein. This response is dependent upon the number of tumour cells injected into the host. Uptake of Zn into liver and its specific accumulation in a Zn-binding protein, identified as metallothionein, continues for a number of days and reaches a plateau as tumour growth ceases. Over this time period, plasma copper rises. This redistribution also occurs in mice pretreated with cadmium in their drinking water for 1 month at levels of 20, 50, and 100 micrograms/ml. However, in each case there is a lag of 3 days before Zn increases in the livers of these animals which already contain substantial amounts of Cd/Zn-metallothionein. When Ehrlich cells are injected into mice previously placed on a Zn-deficient diet for several days, plasma Zn is already low and no net uptake of Zn into liver metallothionein is apparent. Finally, it is shown that ascites fluid can itself stimulate a transient shift of host of Zn into liver. Heat-inactivated fluid loses this property. It is suggested that, in the peritoneum, tumour cells initiate a stress response mediated by an ascites-fluid factor.

| S-EPMC1152990 | biostudies-other

Zinc-, copper- and cadmium-binding protein in Ehrlich ascites tumour cells.

Project description:The properties of Ehrlich ascites tumour cells exposed in vivo to cadmium were investigated as a function of the zinc status of the host animals. Tumour-cell growth was inhibited by cadmium in both zinc-sufficient and zinc-deficient animals. However, cells in zinc-sufficient tumours accumulate much less cadmium than those in deficient tumours. The subcellular distributions of cadmium and zinc do not depend on zinc status. Cadmium and zinc are bound to a low-molecular-weight protein with properties similar to metallothionein. Without exposure to cadmium, a zinc- and copper-binding protein is still present that behaves like a metallothionein. This protein can rapidly bind cadmium added to Ehrlich cells in vitro. It is shown that the zinc- and copper-binding protein contains free thiol groups. Ehrlich cells isolated from cadmium-treated animals are viable and show normal incorporation of uridine into RNA, but the cellular uptake of thymidine and its incorporation into DNA are inhibited.

| S-EPMC1161921 | biostudies-other

The transport and oxidation of succinate by Ehrlich ascites-tumour cells.

Project description:The transport and oxidation of succinate by functionally intact Ehrlich ascites-tumour cells was investigated. On the basis of pH dependence and inhibitor sensitivity it was concluded that succinate may be transported across the cell membrane by the organic anion carrier system. Thus the ability of isolated Ehrlich cells to oxidize succinate is real, and is not necessarily a result of damage to cell integrity.

| S-EPMC1164208 | biostudies-other

INHIBITION OF PRUINE PHOSPHORIBOSYLTRANSFERASES OF EHRLICH ASCITES-TUMOUR CELLS BY 6-MERCAPTOPURINE.

Project description:1. The formation of adenosine 5'-phosphate, guanosine 5'-phosphate and inosine 5'-phosphate from [8-(14)C]adenine, [8-(14)C]guanine and [8-(14)C]hypoxanthine respectively in the presence of 5-phosphoribosyl pyrophosphate and an extract from Ehrlich ascites-tumour cells was assayed by a method involving liquid-scintillation counting of the radioactive nucleotides on diethylaminoethylcellulose paper. The results obtained with guanine were confirmed by a spectrophotometric assay which was also used to assay the conversion of 6-mercaptopurine and 5-phosphoribosyl pyrophosphate into 6-thioinosine 5'-phosphate in the presence of 6-mercaptopurine phosphoribosyltransferase from these cells. 2. At pH 7.8 and 25 degrees the Michaelis constants for adenine, guanine and hypoxanthine were 0.9 mum, 2.9 mum and 11.0 mum in the assay with radioactive purines; the Michaelis constant for guanine in the spectrophotometric assay was 2.6 mum. At pH 7.9 the Michaelis constant for 6-mercaptopurine was 10.9 mum. 3. 25 mum-6-Mercaptopurine did not inhibit adenine phosphoribosyltransferase. 6-Mercaptopurine is a competitive inhibitor of guanine phosphoribosyltransferase (K(i) 4.7 mum) and hypoxanthine phosphoribosyltransferase (K(i) 8.3 mum). Hypoxanthine is a competitive inhibitor of guanine phosphoribosyltransferase (K(i) 3.4 mum). 4. Differences in kinetic parameters and in the distribution of phosphoribosyltransferase activities after electrophoresis in starch gel indicate that different enzymes are involved in the conversion of adenine, guanine and hypoxanthine into their nucleotides. 5. From the low values of K(i) for 6-mercaptopurine, and from published evidence that ascites-tumour cells require supplies of purines from the host tissues, it is likely that inhibition of hypoxanthine and guanine phosphoribosyltransferases by free 6-mercaptopurine is involved in the biological activity of this drug.

| S-EPMC1206406 | biostudies-other

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data