Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The effect of ethionine on ribonucleic acid synthesis in rat liver.

ABSTRACT: 1. By 1h after administration of ethionine to the female rat the appearance of newly synthesized 18SrRNA in the cytoplasm is completely inhibited. This is not caused by inhibition of RNA synthesis, for the synthesis of the large ribosomal precursor RNA (45S) and of tRNA continues. Cleavage of 45S RNA to 32S RNA also occurs, but there was no evidence for the accumulation of mature or immature rRNA in the nucleus. 2. The effect of ethionine on the maturation of rRNA was not mimicked by an inhibitor of protein synthesis (cycloheximide) or an inhibitor of polyamine synthesis [methylglyoxal bis(guanylhydrazone)]. 3. Unlike the ethionine-induced inhibition of protein synthesis, this effect was not prevented by concurrent administration of inosine. A similar effect could be induced in HeLa cells by incubation for 1h in a medium lacking methionine. The ATP concentration in these cells was normal. From these two observations it was concluded that the effect of etionine on rRNA maturation is not caused by an ethionine-induced lack of ATP. It is suggested that ethionine, by lowering the hepatic concentration of S-adenosylmethionine, prevents methylation of the ribosomal precursor. The methylation is essential for the correct maturation of the molecule; without methylation complete degradation occurs.

SUBMITTER: Swann PF

PROVIDER: S-EPMC1165748 | biostudies-other | 1975 Sep

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Effect of allylisopropylacetamide on Nuclear Ribonucleic Acid synthesis in rat liver.

Project description:The porphyrogenic drug allylisopropylacetamide, a potent inducer of delta-aminolaevulinate synthetase, specifically increases nucleoplasmic RNA synthesis in rat liver. The drug-mediated increase in nucleoplasmic RNA synthesis is blocked by cycloheximide and haemin, which also inhibit the enzyme induction.

| S-EPMC1165390 | biostudies-other

Studies of the ethylation of rat liver transfer ribonucleic acid after administration of L-ethionine.

Project description:1. The ethylated nucleosides present in tRNA isolated from the livers of rats treated with 0.5g of l-ethionine/kg body wt. were investigated. Evidence that this tRNA contained N(2)-ethylguanine, N(2)N(2)-diethylguanine, N(2)-ethyl-N(2)-methylguanine, 7-ethylguanine, two ethylated pyrimidines and ethylated ribose groups was obtained. 2. Ethylation of bacterial tRNA was catalysed by extracts containing tRNA methylases prepared from rat liver by using S-adenosyl-l-ethionine as an ethyl donor, but the rate of ethylation was 20 times less than the rate of methylation with S-adenosyl-l-methionine as a methyl donor. 3. The principal product of such ethylation in vitro was N(2)-ethylguanine and traces of the other ethylated guanines and pyrimidines found in tRNA isolated from rats treated with ethionine in vivo were also found. 1-Ethyladenine was not formed, although 1-methyl-adenine is a major product of methylation of bacterial tRNA by these extracts, and 1-ethyladenine was not present in the rat liver tRNA isolated from ethionine-treated animals. 4. After injection of actinomycin D (15mg/kg body wt.) or l-methionine (1.0g/kg body wt.) before the ethionine, ethylation of tRNA was diminished by about 80% but not completely abolished. Administration of 1-aminocyclopentanecarboxylic acid (2.5g/kg body wt.) to inhibit the formation of S-adenosyl-l-ethionine inhibited ethylation of tRNA by 44%. 5. These results suggest that not all of the ethylation of tRNA that occurs in the livers of rats treated with ethionine is mediated by the action of tRNA methylases acting with S-adenosyl-l-ethionine as a substrate, but that this pathway does occur and accounts for a major part of the observed ethylation. 6. The results are discussed with reference to ethionine-induced hepatocarcinogenesis.

| S-EPMC1173570 | biostudies-other

Synthesis of ribonucleic acid by isolated rat liver mitochondria.

Project description:Rat liver mitochondria isolated in sucrose-N-tris(hydroxymethyl)methyl-2-aminoethane-sulphonic acid (TES) incorporated [(3)H]UTP into RNA for 1h. Incorporation was inhibited 50% by 1mug of actinomycin D/ml, 1mug of acriflavine/ml and 0.5mug of ethidium bromide/ml but was insensitive to rifampicin, rifamycin SV, streptovarcin and deoxyribonuclease. After the first 10min of incubation, the synthesis was insensitive to ribonuclease. RNA synthesis by mitochondria isolated in sucrose-EDTA was insensitive to actinomycin D and sensitive to ribonuclease during the first 10min of the incubation but thereafter the sensitivities were the same as for mitochondria isolated in sucrose-TES. In a hypo-osmotic medium the relative extent of incorporation of the four ribonucleoside triphosphates into RNA was CTP>UTP=ATP>>GTP. In an iso-osmotic medium the incorporation of CTP and GTP decreased. All four nucleotides were incorporated into RNA in a DNA-dependent process, as indicated by the inhibition by actinomycin D. In addition, CTP and ATP were incorporated into the CCA end of mitochondrial tRNA. ATP was also incorporated into an unidentified acid-insoluble compound, which hydrolysed in alkali to a product that was not ATP, ADP or 5'- or 2(3')-AMP. Atractyloside inhibited the incorporation of ATP into RNA with 50% inhibition at 2-3nmol/mg of protein. The [(3)H]UTP-labelled RNA had peaks of 16S and 13S characteristic of mitochondrial rRNA. In addition a peak at 20-21S was observed as well as heterogeneous RNA sedimenting throughout the gradient. The synthesis of all these species was inhibited by actinomycin D, indicating that rat liver mitochondrial DNA codes for mitochondrial rRNA as well as other as yet unidentified species.

| S-EPMC1173765 | biostudies-other

Ribonucleic acid synthesis in isolated rat liver nuclei under conditions of ribonucleic acid processing and transport.

Project description:A cell-free system is described which permits a significant and prolonged synthesis of RNA in isolated rat liver nuclei, under conditions previously demonstrated to support normal nuclear processing and transport of both rRNA and mRNA. The system contains cytosol but not (NH4)2SO4 or other non-physiological components. Evidence is presented for cytosol factors which stimulate ribosomal, and to a lesser degree, non-ribosomal RNA synthesis.

| S-EPMC1165430 | biostudies-other

Effect of ethionine treatment on the activity of enzymes concerned with urea synthesis in rat liver.

Project description:1. The activities of the enzymes of the urea cycle were measured in rat liver after feeding with a diet containing ethionine for 2 weeks. This treatment resulted in a decrease in the activity of ornithine transcarbamoylase, which fell to half the control value, while arginase increased by about 40%. The remaining enzymes of the urea cycle were unchanged at this time of treatment. These results are discussed in relation to the known effects of ethionine on nucleic acid synthesis. 2. The activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were measured in rat liver after feeding with a diet containing ethionine for 2 or 5 weeks. At the shorter time-period glucose 6-phosphate-dehydrogenase activity was more than doubled but 6-phosphogluconate-dehydrogenase activity remained unchanged. 3. The results are compared with similar measurements made after feeding with diets containing 4-dimethylamino-3'-methylazobenzene for 2 weeks. Striking similarities were found in the pattern of change in the enzyme activities of each of the pathways in the two treatments.

| S-EPMC1265069 | biostudies-other

The effect of aflatoxin B 1 on normal and cortisol-stimulated rat liver ribonucleic acid synthesis.

Project description:1. Aflatoxin B(1), administered in vivo, inhibits the incorporation of [(14)C]orotic acid in vivo into rat liver nuclei, and also inhibits both Mg(2+)- and Mn(2+)-dependent RNA polymerase activities in nuclei assayed in vitro. 2. Aflatoxin B(1) inhibits the cortisol-induced increase in incorporation of [(14)C]leucine in vivo, but does not affect the control value of this activity. 3. Aflatoxin B(1) administered in vivo inhibits the increase in nuclear Mg(2+)-dependent RNA polymerase activity, assayed in vitro, which results from the treatment with cortisol. 4. Adrenalectomy causes a decrease in Mg(2+)-dependent RNA polymerase activity. The effect on this enzymic activity of adrenalectomy plus treatment with aflatoxin B(1) is no greater than that of treatment with aflatoxin B(1) alone. 5. These results suggest that the inhibition of cortisol-stimulated biochemical pathways by aflatoxin B(1) is due to an inhibition of cortisol-stimulated RNA synthesis. 6. The cytoplasmic action of aflatoxin is thought to be due to a competition for receptor sites on the endoplasmic reticulum between steroid hormones and aflatoxin B(1). No evidence was obtained for a similar competition for nuclear receptor sites between [(3)H]cortisol and aflatoxin B(1). 7. No differences were observed between the activities of RNA polymerase preparations solubilized from control or aflatoxin-inhibited nuclei. 8. No differences in ;melting' profiles were observed between DNA and chromatin preparations isolated from control nuclei or from aflatoxin-inhibited nuclei. 9. It is suggested that aflatoxin B(1) exerts its effect on RNA polymerase by decreasing the template capacity of the chromatin and that the aflatoxin ;target' area of the chromatin includes that region which is stimulated by cortisol. This process, however, does not involve inhibiting the movement of cortisol from the outside of the hepatic cell to the nuclear chromatin.

| S-EPMC1174442 | biostudies-other

Decreased ribonucleic acid synthesis in isolated rat liver nuclei during starvation.

Project description:1. Isolated nuclei from starved rats showed a lowered incorporation of [(14)C]UMP into RNA. 2. The Mg(2+)-dependent incorporation was decreased by 30% after 1 day of starvation, but incorporation in the presence of Mn(2+) and ammonium sulphate decreased only after longer periods of starvation. 3. RNA synthesis by nuclei in the presence of excess of added RNA polymerase was unchanged after 1 day of starvation and was inhibited by 20% after 4 days. 4. The capacity of nuclei to bind actinomycin D was unchanged after 1 day and was decreased by 20% after 4 days of starvation.

| S-EPMC1179608 | biostudies-other

Effect of hypophysectomy on liver nuclear ribonucleic acid synthesis in aging rats.

Project description:Changes in RNA synthesis in liver nuclei were observed at different ages and after hypophysectomy and hormone replacement in female Sprague-Dawley rats. As determined by the incorporation of [3H]UMP into an acid-insoluble product, RNA synthesis decreased by about 75% in intact rats from 6 months to 24 months of age. This decline with age was not observed in liver nuclei from 24-month-old rats that had been hypophysectomized at 12 months and maintained on a minimal hormone-replacement therapy. Thyroid hormones and somatotropin (growth hormone) had an additive effect on RNA synthesis in liver nuclei from these hypophysectomized rats. The same hormones had no significant effect on intact, age-matched rats. With advancing age, nuclei of intact rats had an increase in the pool of free RNA polymerase and an apparent decrease in the enzyme activity bound to nuclear chromatin. There was no change in total enzyme with age. In hypophysectomized, hormone-treated rats, free RNA polymerase activity decreased and chromatin-bound activity increased. There was no difference in total nuclear RNA polymerase activity between operated or intact rats. However, the ratio of the bound to the free activity was different. These results suggest that the ability of RNA polymerase to bind to chromatin may be involved in the age-related decrease in liver nuclear RNA synthesis of intact rats.

| S-EPMC1161852 | biostudies-other

Effect of chloramphenicol on ribonucleic acid synthesis in liver cells in suspension.

Project description:1. Chloramphenicol has a stimulatory effect on the incorporation of radioactive phosphate into the RNA of perfused rat-liver slices, whole liver homogenates or the liver-cell suspensions, and no effect on the incorporation of [(14)C]adenine and [(14)C]uracil into the RNA of the tissue slices. 2. Chloramphenicol completely inhibits the incorporation of labelled adenine and uracil into the RNA of the cell suspensions, or into the RNA of homogenates derived from the whole liver tissues. 3. Chloramphenicol has at most a slight inhibitory effect on the transport of labelled adenine or uracil in the hepatic cells in suspension; in the slices, the transport of these bases is not inhibited at all. 4. The above observations indicate that: (a) unlike the tissue slices, hepatic cells in suspension are permeable to chloramphenicol; (b) in the presence of chloramphenicol, for reasons that are not clear, the conversion of the base into the appropriate nucleotide does not proceed.

| S-EPMC1264544 | biostudies-other

Evidence for ethylation of rat liver deoxyribonucleic acid after administration of ethionine.

Project description:1. Administration of a large dose (500mg/kg body wt.) of (3)H-labelled l-ethionine to rats resulted in the incorporation of a small amount of radioactivity into the liver DNA. Considerable evidence that this radioactivity was not due to contamination of the isolated DNA with labelled protein, RNA, S-adenosyl-l-ethionine or l-ethionine was obtained. 2. After acidic hydrolysis of the DNA isolated from the livers of rats treated with labelled l-ethionine, virtually all of the radioactivity present in the DNA was found in a fraction with similar chromatographic properties to 7-ethylguanine. 3. Treatment of rats with comparable doses of l-methionine did not lead to the formation of 7-methylguanine in the liver DNA. 4. These results are discussed in relation to the induction of liver tumours by ethionine.

| S-EPMC1176921 | 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