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PubMed1978

Selective inhibition of uracil tRNA methylases of E. coli by ethionine.

L-ethionine has been found to inhibit uracil tRNA methylating enzymes in vitro under conditions where methylation of other tRNA bases is unaffected. No selective inhibitor for uracil tRNA methylases has been identified previously. 15 mM L-ethionine or 30 mM D,L-ethionine caused about 40% inhibition of tRNA methylation catalyzed by enzyme extracts from E. coli B or E. coli M3S (mixtures of methylases for uracil, guanine, cytosine, and adenine) but did not inhibit the activity of preparations from an E. coli mutant that lacks uracil tRNA methylase. Analysis of the 14CH3 bases in methyl-deficient E. coli tRNA after its in vitro methylation with E. coli B3 enzymes in the presence or absence of ethionine showed that ethionine inhibited 14CH3 transfer to uracil in tRNA, but did not diminish significantly the 14CH3 transfer to other tRNA bases. Under similar conditions 0.6 mM S-adenosylethionine and 0.2 mM ethylthioadenosine inhibited the overall tRNA base methylating activity of E. coli B preparations about 50% but neither of these ethionine metabolites preferentially inhibited uracil methylation. Ethionine was not competitive with S-adenosyl methionine. Uracil methylation was not inhibited by alanine, valine, or ethionine sulfoxide. It is suggested that the thymine deficiency that we found earlier in tRNA from ethionine-treated E. coli B cells, resulted from base specific inhibition by the amino acid, ethionine, of uracil tRNA methylation in vivo.

Amino Acids↗
PubMed1975

Ethionine-induced changes in rat liver transfer RNA methylation.

We have confirmed the finding by Rajalakshmi that transfer RNA (tRNA) from livers of ethionine-treated rats can act as a substrate for homologous tRNA-methylating enzymes in vitro. This methyl-deficient tRNA from liver can be methylated in vitro by enzymes from normal or ethionine-treated rats. The in vitro inhibition of tRNA methylation that follows ethionine treatment can be at least partially relieved in vitro. The liver extracts from ethionine-treated animals contained a low-molecular-weight inhibitor of tRNA methylation. Dialysis of enzyme preparations from ethionine-treated, but not control, rats resulted in large increases in tRNA methylase activity, with either Escherichia coli or homologous tRNA's as substrate. Furthermore, the tRNA methylase activity of control rat liver enzyme extracts was greatly depressed by dialysate from liver homogenates of ethionine-treated rats. After 5 days of ethionine administration the liver tRNA methylase activities were significantly higher than those of control preparations despite the continued presence of the dialyzable inhibitor(s). The liver tRNA's from these animals were poorer methyl acceptors than those from 3-day-treated rats, although still better than tRNA's from untreated rats. These observations have been interpreted to indicate that ethionine causes the accumulation in the liver of inhibitors of tRNA methylation. Early in the course of ethionine administration, methyl-deficient tRNA can be isolated. When the period of ethionine treatment is extended, the organism attempts to maintain homeostasis by production of increased amounts of tRNA-methylating enzymes. The increased quantities of these enzymes are able to overcome, at least partially, the effects of the inhibitors and to decrease the extent to which methyl-deficient tRNA is produced.

Animals↗
PubMed1979

[Effects of thiol compounds on experimental liver damage (II). Preventive and therapeutic effects of tiopronin (2-mercaptopropionylglycine) and glutathione on ethionine induced liver damage (author's transl)].

Preventive and therapeutic effects of tiopronin (2-mercaptopropionylglycine) and glutathione on ethionine induced liver damage were studied. Administration of 1 g/kg ethionine resulted in significant differences in the degree of liver damage, and such was dependent on the feeding conditions of the animals. The present experiment was performed under the conditions where the most serious liver damage was observed. In the experiment on the preventive effects, serum GOT and GPT were markedly elevated by ethionine, but such elevation could be suppressed by administering tiopronin or glutathione 10 min before ethionine administration. Liver nonprotein thiol (NPSH) content decreased by 40--60% of the normal level 16 hr after ethionine adminstration, but increased by 30--45% 24 hr later. Administration of tiopronin suppressed the initial fall of liver NPSH content caused by ethionine, but this tendency was not observed in the glutathione treatment. Both liver cholesterol and triglyceride increased in the ethionine treated rats, and triglycerides in particular decreased with administration of tiopronin or glutathione. In the experiment on the therapeutic effects, the maximal values of serum GOT and GPT brought by ethionine were suppressed by the thiol compounds given 16 hr after ethionine administration, but liver NPSH content and liver lipids were not influenced. Thus, tiopronin and glutathione are considered to have preventive and therapeutic effects on liver damage induced by ethionine.

Amino Acids, Sulfur↗
PubMed1983

Mutagenesis and anti-mutagenesis in Salmonella: influence of ethionine and caffeine on yields of mutations induced by 2-aminopurine and 9-aminoacridine.

Ethionine, the ethyl analogue of methionine, slightly reduced the yield of reversions of the hisC3076 frameshift marker induced by 9-aminoacridine (9AA) in an excision-proficient strain of Salmonella typhimurium, but completely abolished mutagenesis by 9AA in the excision-deficient uvrB-deletion strain TA1537. No toxic effects of ethionine were apparent in either the excision-proficient or the excision-deficient strain. Because of the differential effects of ethionine on mutagenesis in the two strains, it seemed possible that an ethionine-sensitive step in the process(es) leading to fixation of 9AA-induced mutations might be compensated for by the uvrA,B,C+ excision-repair system. To further test this possibility, we used caffeine (a compound known to significantly reduce the efficacy of the excision-repair process) as a co-treatment with ethionine for cells of an excision-proficient strain exposed to 9AA. Treatment with caffeine alone or ethionine alone had very little effect on reversion yield, whereas co-treatment with the two agents abolished 9AA mutagenesis. It appeared, therefore, that either the caffeine-sensitive pathway or the ethionine-sensitive pathway needed to be functioning if 9AA-induced reversions of hisC3076 marker were to be detected. Addition of methionine to cells of the excision-deficient strain exposed to 9AA restored their ability to be mutated by 9AA, however. In a base-pair substitution back-mutation system, ethionine slightly enhanced the yields of revertants of the trpE8 marker induced by 2-aminopurine (2AP) in both an excision-proficient strain (at all 2AP dose levels tested) and an excision-deficient strain (only at the lower dose levels). In the excision-deficient strain, doses of 2AP above 300 micrograms/plate were highly toxic when ethionine was also present. It was for this reason that no 2AP-induced revertants were recovered at the higher 2AP concentrations. Treatment of the trpE8 strain with methionine also enhanced the yield of 2AP-induced revertants of this marker.

2-Aminopurine↗
PubMed1982

Effects of ethionine treatment of protein-synthesizing apparatus of rat liver 80 S ribosomes and 40 S ribosomal subunits.

The inhibitory effects of ethionine treatment of female rats for 4 h on the protein-synthesizing machineries of 80 S ribosomes and 40 S ribosomal subunits of the liver were investigated. The following results were obtained. (1) The translation of globin mRNA by 80 S ribosomes or 40 S ribosomal subunits, in combination with mouse 60 S subunits, was markedly inhibited by ethionine treatment in a complete cell-free system containing partially purified initiation factors of rabbit reticulocytes and the rat liver pH 5 fraction. (2) The polysome formation of 80 S ribosomes in the complete system described above was inhibited by ethionine treatment. Similar inhibitions by ethionine treatment were observed in the case of incubation of 40 S subunits with reticulocyte lysate, although the polysome formation was rather low even in the case of control 40 S subunits. (3) The pattern of CsCl isopycnic centrifugation of rat liver native 40 S subunits uniformly labeled with [14C]- or [3H]orotic acid showed that the content of non-ribosomal proteins of native 40 S subunits was decreased by ethionine treatment. The analysis of proteins of native 40 subunits by SDS-polyacrylamide slab gel electrophoresis revealed that eIF-3 subunits and two unidentified protein fractions of molecular weight of 2.3.10(4) and 2.1.10(4) were decreased in ethionine-treated rate liver. (4) 40 S subunits from ethionine-treated or control rat livers were labeled with N-[3H]ethylmaleimide or N-[14C]ethylmaleimide, and the 3H to 14C ratios of individual 40 S proteins on two-dimensional polyacrylamide gel electrophoresis were measured. The results suggested that the conformation of rat liver 40 S subunits was changed by ethionine treatment. (5) These results may indicate that ethionine treatment decreases the activity of rat liver 40 S subunits for the interaction with initiation factors, especially eIF-3, as the results of conformational changes of 40 S subunits.

Animals↗
PubMed1972

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

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.

Animals↗
PubMed1988

Formation of S-adenosylethionine in liver of rats chronically fed with DL-ethionine.

The early changes in the metabolism of L-ethionine were examined in rats preexposed to chronic administration of DL-ethionine. The capacity of liver to accumulate S-adenosylethionine after a single injection of L-ethionine decreases rapidly from the onset of the carcinogenic regimen. This drop is caused by diminished S-adenosylethionine synthesis, a consequence of lower activity of the ATP-L-methionine adenosyltransferase. This change is accompanied by the rapid increase of the concentration of free ethionine and ethionine sulfoxide. The concentration of hepatic ATP depends in the control animals on the L-ethionine dose and is inversely related to the S-adenosylethionine concentration, but in DL-ethionine-pretreated rats it becomes gradually independent of the L-ethionine dose. The alterations in L-ethionine metabolism observed are not attributed to the change in the ratio of hepatocytes to oval cells but rather to the functional alterations of hepatocytes.

Adenosine↗
PubMed1980

In vivo D-ethionine inversion and its inhibition.

The quantitative study of the inversion of D-ethionine into L-ethionine in vivo, measured in the liver of rats by the formation of S-adenosylethionine from L-ethionine, demonstrates high efficiency of this conversion when lower doses of D-ethionine are used. At higher doses (> 25 mg (80 mumol)/100 g body wt) the accumulation of S-adenosylethionine is retarded. It is suggested that this decrease of S-adenosylethionine formation is due to an unknown as yet effect of D-ethionine on the L-ethionine metabolism. At these higher doses, the alternative assay of the inversion, based on determining the dilution of radioactive L-ethionine probes by inverted D-ethionine, demonstrates considerably higher inversion, supporting the previous assumption. The inversion can be inhibited by administering D-ethionine simultaneously with either kojic acid or sodium benzoate, both inhibitors of D-amino acid oxidase. Sodium benzoate administration is tolerated very well by rats and therefore may be used in chronic experiments.

Animals↗
PubMed1965

EFFECT OF ETHIONINE ON THE RIBONUCLEIC ACID, DEOXYRIBONUCLEIC ACID, AND PROTEIN CONTENT OF ESCHERICHIA COLI.

Smith, Robert C. (Auburn University, Auburn, Ala.), and W. D. Salmon. Effect of ethionine on the ribonucleic acid, deoxyribonucleic acid, and protein content of Escherichia coli. J. Bacteriol. 89:687-692. 1965.-The addition of ethionine to cultures of Escherichia coli K-12 W6, a methionine-requiring auxotroph, led to inhibition of the rate of increase in optical density when the ratio of ethionine to methionine was 200:1. When the ratio was 600:1, the increase in optical density became linear. When ethionine was substituted for methionine in the medium, the optical density of the culture increased, and there was a parallel increase in protein content. There was no cell division in these cultures. The rate of synthesis of ribonucleic acid (RNA) in a culture containing ethionine was similar to that of a culture deprived of methionine, but the synthesis of deoxyribonucleic acid in a culture with ethionine was about twice that of a culture deprived of methionine. No detectable radioactivity from ethionine-ethyl-1-C(14) was incorporated into RNA. Ethionine-ethyl-1-C(14) was readily incorporated into the protein fraction.

Amino Acids↗
PubMed1986

Induction of hyperphenylalaninemia in mice by ethionine and phenylalanine.

Female NMRI mice were fed diets containing l-ethionine (0.1 and 0.3% w/w) and phenylalanine (3% w/w), as well as respective control diets. Ethionine, the S-ethylated analog of methionine, was shown to inhibit phenylalanine hydroxylase in vivo, whereby in vitro kinetics remained unaffected. Treatment with ethionine resulted in fatty liver, reduced ATP content of liver, and alterations in serum amino acid concentrations. In the high dosage ethionine group, for instance, concentrations of Ala, Gly, Ser, Met, and Phe were increased whereas concentrations of Lys, Asp, and Pro were decreased. Applying ethionine together with phenylalanine resulted in hyperphenylalaninemia and phenylketonuria. Feeding phenylalanine alone also led to decreased activity of phenylalanine hydroxylase and increased concentration of Phe in serum. Ethionine only had a minimal effect on body weight gain; however, the hyperphenylalaninemic condition induced by application of the high dosage of ethionine and phenylalanine induced severe loss of body weight. A disturbed protein synthesis and protein phosphorylation might be the underlying mechanism of ethionine-induced suppression of phenylalanine hydroxylase.

Adenosine Triphosphate↗
PubMed1983

Neoplastic conversion of rat liver epithelial cells in culture by ethionine and S-adenosylethionine.

Rat liver epithelial cells were grown in the presence of the hepatocarcinogen, DL-ethionine, for 12 weeks. The cells were then cultured for an additional 32 weeks in carcinogen-free medium. At approximately monthly intervals, the cells were tested for transformation by assaying their ability to grow in soft agar and to produce tumors when injected s.c. into irradiated syngeneic rats. After a total of 34 weeks in culture, cells treated with 7.5 mM DL-ethionine were transformed according to both criteria. The experiment was repeated using medium in which methionine was replaced by its metabolic precursor, homocysteine. The cells were treated for 12 weeks with L-ethionine and its metabolite, S-adenosyl-L-ethionine (L-AdoEt), then cultured in their absence in methionine-containing medium for an additional 24 weeks. After a total of 20 weeks in culture, cells treated with 0.375 mM L-ethionine and cells treated with 0.2 mM L-AdoEt produced tumors following their injection into animals. Positive growth in soft agar was observed 5 and 11 weeks later, respectively. A total of 31 weeks in culture was required before cells treated with 0.2 mM L-ethionine became tumorigenic. Furthermore, tumors resulting from the injection into animals of cells treated with 0.2 mM L-ethionine arose 8-10 weeks later than did the corresponding tumors arising from the cells treated with 0.2 mM L-AdoEt. Thus, the results indicate that AdoEt may be a proximal carcinogenic metabolite of ethionine.

Adenosine↗
PubMed1984

Hypomethylation of DNA in ethionine-fed rats.

Ethionine, the hepatocarcinogenic antimetabolite of methionine, was fed to rats in carcinogenic doses for 1-10 weeks. Levels of 5-methyldeoxycytidine (5-MC) in nuclear DNA and total cellular levels of S-adenosylmethionine (AdoMet) and S-adenosylethionine (AdoEt) were determined at 1, 5 and 10 weeks in livers of control and ethionine-treated animals. The percentage of deoxycytidine residues modified to 5-MC in hepatic DNA of ethionine-fed animals was the same as that in the control animals at 1 week but was 3.6% and 7.6% lower than that observed in control animals at 5 and 10 weeks, respectively. Significant levels of AdoEt, a DNA methylase inhibitor, as well as decreases in the levels of AdoMet were also observed in the livers of ethionine-fed animals. In a second study, the levels of 5-MC, AdoMet and AdoEt were determined in the pancreas, kidneys, testes and thymus of control rats and rats fed ethionine for 10 weeks. Only the testes, an organ known to be susceptible to the toxic effects of ethionine, showed a significant (p less than 0.02) decrease in 5-MC in response to ethionine feeding. AdoEt was present in all tissues studied, except thymus, but at lower levels than those observed in the liver. These results demonstrate that ethionine administration alone under conditions which cause tumors is sufficient for the production of hypomethylated DNA in the target organ and one extrahepatic tissue studied. Hypomethylation of hepatic DNA would appear to result from the accumulation of AdoEt coupled with the decreased levels of AdoMet.

Adenosine↗
PubMed1977

Effect of dietary DL-ethionine and/or DL-methionine on egg laying and activities of some cytoplasmic NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica.

The effect of dietary DL-ethionine and/or DL-methionine on egg laying, and activities of some NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica was investigated. A 0.30% DL-ethionine plus 0.30% DL-methionine supplemented diet reversed partially the egg laying inhibited by the diet with 0.30% DL-ethionine alone. No inhibitory effect on egg laying was observed for the diet supplemented with 0.30% DL-methionine alone. In marked contrast to the decreased activity of L-glycerol 3-phosphate dehydrogenase and malate dehydrogenase, significantly increased activity of lactate dehydrogenase was obtained for quail fed the DL-ethionine, and the DL-ethionine plus the DL-methionine supplemented diet, respectively. No marked changes in activities of these three dehydrogenases were obtained for quail fed the diet supplemented with DL-methionine alone. Although decreased activity was observed for all of the four NADPH-producing enzymes in quail fed the diet supplemented with DL-ethionine alone, the DL-ethionine plus DL-methionine, the smallest decrease was obtained for NADP-isocitrate dehydrogenase. The diet supplemented with DL-methionine alone induced markedly the respective activity of malic enzyme and glucose 6-phosphate dehydrogenase. These results indicate a relatively important function of NADP-isocitrate dehydrogenase for NADPH-production even under DL-ethionine toxicity and suggest complicated relationships between egg production and activities of enzymes associated with carbohydrate and lipid metabolism in quail liver.

Alcohol Oxidoreductases↗
PubMed1982

Role of 3-ethylthiopropionate in ethionine metabolism and toxicity in rats.

The potential role of the pathway for ethionine catabolism involving the intermediate formation of 3-ethylthiopropionate in the etiology of ethionine hepatotoxicity was studied in rats. Rats were fed diets containing graded levels of 3-ethyl-thiopropionate, an intermediate of this pathway, for three weeks. A dietary level as low as 0.4% was toxic to rats, resulting in depressed growth and food intake, decreased blood hemoglobin levels and darkened and enlarged spleens. All animals fed 3-ethylthiopropionate expired a volatile sulfur compound that was identified as ethanethiol by gas chromatography using both a general flame ionization detector and a sulfur specific flame photometric detector. Rats fed diets containing either 0.8% ethionine or 3-ethylthiopropionate exhibited an 80% decrease in body weight gain over a three-week period compared to controls. Spleens were markedly darkened and enlarged and spleen iron content was 6-fold and 1.5-fold higher than controls in 3-ethylthiopropionate-fed and ethionine-fed rats, respectively. Liver concentrations of reduced and total glutathione were 30% higher than controls in ethionine-fed rats. There results document the marked toxicity of 3-ethylthiopropionate and ethionine and suggest that this pathway for ethionine catabolism may be involved in some of the numerous reported metabolic aberrations as a result of acute or chronic ingestion of ethionine.

Animals↗
PubMed1995

Prevention by methionine of enhancement of hepatocarcinogenesis by coadministration of a choline-deficient L-amino acid-defined diet and ethionine in rats.

The effects of methionine on hepatocarcinogenesis induced by coadministration of a choline-deficient L-amino acid-defined (CDAA) diet and ethionine were examined. F344 male rats were divided into 4 experimental groups. Groups 1 and 2 received the CDAA diet and a choline-supplemented L-amino acid-defined (CSAA)++ diet, respectively. Group 3 received the CDAA diet containing 0.05% ethionine, and group 4 the CDAA diet containing 0.05% ethionine and 0.47% methionine. Animals were killed after 12 weeks of treatment. Histologically, the CDAA diet induced intracellular fat accumulation and foci. In contrast, ethionine caused not only foci, but also hyperplastic nodules, cholangiofibrosis and the proliferation of oval cells without such fat accumulation. Methionine abolished the development of all of the liver lesions induced by coadministration of the CDAA diet and ethionine. To investigate the effects of methionine on induction of c-myc and c-Ha-ras expression, as well as generation of 8-hydroxyguanine (8-OHGua) and 2-thiobarbituric acid-reacting substances (TBARS), by coadministration of the CDAA diet and ethionine, subgroups of 3 to 5 animals were killed at 2, 4, 8, or 11 days after the beginning of the experiment. Coadministration of the CDAA diet and ethionine markedly enhanced the level of expression of c-myc and c-Ha-ras, 8-OHGua formation and TBARS generation as compared with the CDAA or CSAA diet within 11 days, and methionine blocks these actions. These results indicate that addition of methionine prevents the induction of c-myc and c-Ha-ras expression, 8-OHGua formation and TBARS generation, as well as hepatocellular lesions, by coadministration of the CDAA diet and ethionine in rats, and suggest a possible involvement of oxidative stress and gene expression in hepatocarcinogenesis by these agents.

Amino Acids↗
PubMed1987

Amelioration of ethionine toxicity in the chick.

Several chick bioassays were conducted to evaluate means of ameliorating ethionine toxicity. Supplementing a corn-soy diet marginally deficient in sulfur amino acids (methionine + cystine) with .075% D,L-ethionine reduced weight gain in 8-day-old chicks by 70% compared to gains of unsupplemented controls. Dietary addition of .50% DL-methionine prevented reduction in weight gain and feed intake resulting from ethionine supplementation whereas feeding supplemental L-cystine was without effect. Supplementation of the ethionine-containing diet with either choline or betaine ameliorated the growth depression, although neither compound was able to completely overcome the toxic effects of ethionine. Dietary ethionine did not affect plasma levels of free methionine or cystine but did increase plasma free glycine 6-fold. Dietary addition of .50% DL-methionine caused normalization of plasma glycine levels whereas it elevated plasma methionine concentration. Although results suggested the possibility of ethionine-induced serine or threonine deficiency, dietary additions of .75% L-serine or .75% L-threonine failed to improve chick weight gain. These studies suggest that ethionine, in addition to affecting transsulfuration and transmethylation activity may exert specific effects on certain amino acids in tissue pools.

Amino Acids↗
PubMed2004

Protective effect of soybean against hepatocarcinogenesis induced by DL-ethionine.

There has been increasing interest in the value of using soybean to delay or reduce the tumor incidence. This study was undertaken to investigate the possible protective effects of soybean against hepatocarcinogenesis induced by DL-ethionine. Accordingly, we measured biochemical changes occurring in serum and liver of rats treated with DL-ethionine in the presence or absence of soybean. Male albino rats were fed a control diet containing the hepatocarcinogen, DL-ethionine, or the control diet plus soybean 30%, or the control diet plus soybean plus DL-ethionine 0.25% for three months and then returned to a control diet for up to nine months. Rats fed a control diet plus DL-ethionine showed a gradual decrease in liver DNA, RNA, total protein, and liver weight and enzyme activities of liver transaminases (GOT and GPT) and alkaline phosphatase over the 7-month study period. This was followed by a large increase in the liver parameters at the end of the 9(th) month, except for 5'-nucleotidase and glucose-6-phosphatase that showed a large decrease. On the other hand, a gradual increase in the serum enzyme activities of GOT, GPT, 5-nucleotidase, alkaline phosphatase, and in the albumin/globulin (A/G) ratio is observed in the group of rats fed a control diet plus DL-ethionine compared to the control group over 8 months, and this was followed by a large increase in all serum parameters studied at nine-months. The administration of 30% soybean to the rat diet in addition to DL-ethionine maintained all parameters studied at near control values until the end of the 9(th) month. This study suggests that soybean has a protective effect against the hepatocarcinogenesis induced by DL-ethionine.

Animals↗
PubMed1976

The influence of DL-methionine on the metabolism of S-adenosylethionine in rats chronically treated with DL-ethionine.

The concentration of S-adenosylethionine in the liver of ethionine-fed rats was increased gradually during the process of carcinogenesis. This increase may have been due to the decreased capacity of the treated rats to acetylate ethionine sulfoxide. Ethionine sulfoxide is considered as the main reserve pool of ethionine for the synthesis of S-adenosylethionine. When the ethionine diet was supplemented by DL-methionine (0.3 to 0.9%), the increase in the concentration of S-adenosylethionine during the period of observation (28 to 150 days) was lower and the acetylation of ethionine sulfoxide was significantly higher. The concentration of the total S-adenosyl compounds in the liver of rats on a diet supplemented with DL-methionine was increased over the concentration of S-adenosylethionine in rats fed ethionine alone, and the S-adenosylethionine portion of this fraction was only about 30% lower. The supplementation of the diet with methionine restored the diurnal oscillation of adenosine 5'-triphosphate in the liver, which had been absent in rats ingesting only ethionine.

Adenosine↗