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Biomedical subjects

K Sorimachi

Publications and source records attributed to K Sorimachi.

At least 73 records · Page 4Linked to original sources
PubMed1983

Induction of tyrosine aminotransferase activity by concanavalin A in cultured rat hepatoma cells.

Concanavalin (Con A) induced tyrosine aminotransferase activity in cultured rat hepatoma cells (R117-21B). The highest level of the induced enzyme activity was observed at 6 to 8 hr of incubation with Con A, and the activity returned to the control level after 24 hr. This enzyme induction was dose-dependent in the range of 0.5 to 5 micrograms Con A per ml, while at higher concentrations (more than 50 micrograms/ml) the induction was very small or absent. The addition of alpha-methyl-D-mannoside abolished the effect of Con A. A 4 hr incubation of the cells with Con A and a subsequent 2 hr incubation was necessary to yield the maximal induction of tyrosine aminotransferase activity. Simultaneous incubation of the cells with Con A (5 micrograms/ml) and insulin or dexamethasone, induced tyrosine aminotransferase activity to levels higher than each activator alone, and the effect of Con A on the induction of tyrosine aminotransferase activity by dexamethasone was almost an additive. It was concluded that Con A at low concentrations mimics insulin in the induction of tyrosine aminotransferase activity in R117-21B cells, and that the effect of Con A and insulin on the induction of the enzyme is different from the effect of dexamethasone on this process.

Animals↗
PubMed1981

High affinity of triiodothyronine (T3) for nonphenolic ring deiodinase and high affinity of tetraiodothyroacetic acid (TETRAC) for phenolic ring deiodinase in cultured monkey hepatocarcinoma cells and in rat liver homogenates.

The metabolism of 3, 5-[3'-125I]triiodothyronin (T3) and 3-[3', 5'-125I]triiodothyronine (rT3) was studied in cultured monkey hepatocarcinoma cells (NCLP-6E), and the deiodinations of these iodothyronines were also investigated in cultured cell homogenates and in rat liver homogenates. The metabolites were analyzed by ion exchange column chromatography. For nonphenolic ring deiodination of 3, 5-[3'-125I]triiodothyronine, the order of the inhibitory effect of excess unlabeled iodothyronine or its analog was as follows: 3,3',5-triiodothyroinine greater than triiodothyroacetic acid greater than tetraiodothyroacetic acid greater than thyroxine. This order did not differ between in the intact cells (NCLP-6E) and their homogenates. The order of effectiveness of the excess unlabeled compounds on phenolic ring deiodination of 3-[3', 5'-125I]triiodothyronine in the intact cells was as follows: tetraiodothyroacetic acid greater than triiodothyroacetic acid, 3, 3', 5-triiodothyronine greater than thyroxine. This order was the same among monkey hepatocarcinoma cell homogenates, rat hepatoma cell homogenates and rat liver homogenates, and triiodothyroacetic acid was obviously more effective than 3, 3', 5-triiodothyronine. It was concluded that 3, 3', 5-triiodothyronine had the highest affinity for nonphenolic ring deiodinase among iodothyronines and their analogs used in the present study and that tetraiodothyroacetic acid and the highest affinity for phenolic ring deiodinase. It seems, therefore, that the metabolites derived from the thyroid hormones might contribute to deiodinations which involve activation and inactivation of the hormones.

Animals↗
PubMed1980

Activation and inactivation of thyroxine by cultured rat hepatoma cells.

The metabolism of thyroxine, 3,3'-triiodothyronine and 3,3',5'-triiodothyronine was investigated in rat hepatoma cell cultures (R117-21B). These iodothyronines were labeled with 125I in the phenolic ring and the metabolites were analyzed by ion-exchange column chromatography. When thyroxine was incubated with the cells at 37 degrees C, its glucuronide was the major product and a little increase in 125I- was detected. Although 3,3',5-triiodothyronine was not observed in the incubation medium, this metabolite was clearly identified in the ethanol extract obtained from the cell homogenates after 24 h incubation. This cell line also metabolized labeled 3,3',5-triiodothyronine added to culture medium. After 24 h incubation, 3,3',5-triiodothyronine glucuronide was the major metabolite and iodothyronine sulfates were also formed. The sulfates contained, 3,3',5-triiodothyronine and 3,3'-diiodothyronine sulfates and an unknown component. In the metabolism of 3,3',5'-triiodothyronine, the cells were very active in carrying out glucuronidation and phenolic ring deiodination, and this metabolism yielded 3,3',5'-triiodothyronine and 3,3'-diiodothyronine glucuronides. The iodide fraction contained a small amount of 3,3'-diiodothyronine sulfate. These results show that the R117-21B rat hepatoma cells metabolize the thyroid hormones and their analogs by phenolic and nonphenolic ring deiodinations, by glucuronidation and by sulfation.

Animals↗
PubMed1980

Phenolic ring deiodination in cultured rat hepatoma cells, and subcellular localization of deiodinases in cultured rat hepatoma, monkey hepatocarcinoma cells and normal rat liver homogenates.

The cultured rat hepatoma cell (R117--21B) homogenates metabolized 3,[3',5'-125I]triiodothyronine by phenolic ring deiodination and produced radioactive iodide and 3,3'-diiodothyronine. Thyroxine (T4) was converted to 3,3',5-triiodothyronine (T3). The production of 125I- represented the deiodination was observed to be pH 6.0--7.0. This enzyme reaction was accelerated by dithiothreitoil. Propylthiouracil strongly inhibited the phenolic ring deiodination at 0.1 mM, whereas an effect of 20 mM methylmercaptoimidazol on the deiodination was very weak or absent. Excess unlabeled iodothyronines (T4, T3 and 3,5-diiodo-L-thyronine) inhibited the phenolic ring deiodination of labeled 3,3',5'-triiodothyronine, although their inhibitory effect was slightly different. Triiodothyroacetic acid was a better inhibitor than T3. Diiodotyrosine did not affect phenolic ring deiodination in cultured rat hepatoma cell homogenates. Phenolic and nonphenolic ring deiodinase activities of cultured monkey hepatocarcinoma cell and rat liver homogenates were also studied by the use of 3,[3',5'-125I]triiodothyronine and [3,5-125I]thyroxine, respectively. Both deiodinase activities were observed in particulate fractions (mitochondrial and microsomal) of cultured cell and rat liver homogenates.

Animals↗
PubMed1980

Continuous culture of Reuber hepatoma cells in serum-free arginine-, glutamine- and tyrosine-deprived chemically defined medium.

The rat hepatoma cell line, H4-II-E, was grown serially over a 1-year period and about 30 passages in arginine-, glutamine-, and tyrosine-deprived and ornithine-supplemented Eagle's minimum essential medium with no supplements other than biotin. The adapted cell line, R-Y121B, proliferates in the above mentioned medium with a doubling time of about 4 days and maintains hepatic "marker" enzymes such as tyrosine aminotransferase, phenylalanine hydroxylase, and all the enzymes of the urea cycle.

Animals↗
PubMed1980

Inhibitory effect of unlabeled iodothyronines on the deiodination of labeled thyroid hormones by cultured hepatocarcinoma cells.

Inhibitory effects of unlabeled iodothyronines on the metabolism of thyroxine (T4), 3,3',5-triiodothyronine (T3) and 3,3',5'-triiodothyronine (reverse T3, rT3) were investigated in continuously cultured monkey hepatocarcinoma cells which showed a rapid metabolism of the thyroid hormones. Nonphenolic ring deiodination of [3',5'-125I]-T4 and [3'-125I]-T3 was strongly inhibited by excess T3, 3,5-diiodothyronine (3,5-T2) and T4, whereas rT3 was the least effective inhibitor. Phenolic ring deiodination of [3,5'-125I]-rT3 was strongly affected by excess unlabeled rT3. However, the inhibitory effect of T4, T3 and 3,5-T3 was much weaker than that of rT3. It was concluded that rT3 is apparently the most effective inhibitor of phenolic ring deiodination but the least effective inhibitor of nonphenolic ring deiodination.

Animals↗
PubMed1980

Metabolism of 3,3'-Diiodothyronine and 3'-monoiodothyronine, and effect of potassium cyanide and dinitrophenol and glucuronidation of thyroxine in cultured rat hepatoma cells.

Rat hepatoma cells (R117-21B) metabolized 3,3'diiodothyronine and 3'-monoiodothyronine by sulfation and glucuronidation. Glucuronidation of iodothyronines (a mixture of 3,3'-diiodothyronine, approximately 99%, and 3'-monoiodothyronine, approximately 10%(was very rapid and 83% of the total 125I in the medium was their glucuronides after 8 hr incubation with the cells at 37 degrees C. Iodothyronine sulfates (approximately 9% of the total 125I) were also detected. No clear increase in free iodide was observed during the 8 hr incubation. The effect of KCN or dinitrophenol on glucuronidation of thyroxine was investigated. Both drugs inhibited glucuronidation, and dinitrophenol was more effective than KCN. Dinitrophenol accelerated the liberation of 125I- in the metabolism of thyroxine in the cultured rat hepatoma cells.

Animals↗
PubMed1979

Phenolic and nonphenolic ring deiodinations of iodothyronines in cultured hepatocarcinoma cell homogenate from monkey.

Iodothyronine monodeiodinase activities in homogenates of cultured monkey hepatocarcinoma cells were measured by the deiodination of [3.5-(125)I]-diiodo-L-thyronine or 3-[3',5'-(125)I]triiodo-L-thyronine (phenolic ring-labeled 'reverse' triiodothyronine). The assay system utilized a small ion-exchange column (AG50W-X4, O.9 X approximately 1 cm) to measure 125I-. Both deiodinases were destroyed by boiling for 1 min. Maximal nonphenolic ring deiodination was observed at pH 7.9 whereas maximal phenolic ring deiodination was at pH 6.3. Both reactions were enhanced strongly by dithiothreitol (0.1-5mM), and slightly by 5 mM beta-mercaptoethanol. Phenolic ring deiodination was strongly inhibited by 0.1 mM propylthiouracil. Nonphenolic ring deiodination was accelerated by EDTA (1.2 MM) and inhibited by Mg(2+) (5mM). Methylmercaptoimidazol and Mg(2+), Ca(2+) and Mn(2+) (0.1-1.0 mM) had little or no effect on either reaction, but Zn(2+) (0.1 mM) strongly inhibited both. Both reactions were inhibited by excess iodothyronine analogues at 10 mM to 10 micron M, and thyroxine was shown to be a competitive inhibitor in both cases. On the basis of relative affinities and inhibitory effects, it appears that the order of affinity for the phenolic ring deiodinase is 3,3',5'-triiodo-L-thyronine(rT3) greater than L-thyroxine(T4) greater than 3,5,3'-triiodo-L-thyronine(T3), whereas for the nonphenolic ring deiodinase the order is T3 greater than T4 greater than rT3. Diiodotyrosine did not affect their deiodination.

Animals↗
PubMed1979

Effects of propylthiouracil and methylmercaptoimidazol on metabolism of thyroid hormones by cultured monkey hepatocarcinoma cells.

Monkey hepatocarcinoma cell monolayer cultures (NCLP-6E) metabolized thyroxine, 3,5,3'-triiodothyronine, 3,3',5'-triiodothyronine and 3,3'-diiodothyronine by phenolic and nonphenolic ring deiodinations and sulfation of the deiodinated products, as shown in previous work with this system. The effects of the antithyroid drugs, propylthiouracil (PTU) and methylmercaptoimidazole (MMI), on these processes was investigated. PTU, at 0.1 and 1 mM, inhibited only phenolic ring deiodination. MMI at 1 mM had no effect, but 32 mM inhibited deiodination of both rings as well as sulfation. The findings suggest that the increased serum rT3 level caused by PTU in vivo is the result of decreased rT3 deiodination, in contrast to the increased rT3 production which is caused by starvation.

Animals↗
PubMed1979

Formation and metabolism of 3',5'-diiodothyronine and 3,5-diiodothyronine by cultured monkey hepatocarcinoma cells.

Cultured monkey hepatocarcinoma cells were incubated with [3',5'-125I] diiodo-L--thyronine and with [3,5-125I] diiodo-L-thyronine. In both instances monodeiodination as well as sulfoconjugation took place. [3.-125I] iodothyronine and [3',5'-125I] diiodothyronine were identified as metabolites of [3'-5'-125I]-L-thyroxine in the cells, but neither [3-125I]-iodothyronine nor [3,5-125I] diiodothyronine was detected after incubation of the cells with ]3,5-125I]-L-thyroxine. No products of diphenyl ether splitting were observed in the medium after incubation of the cells with either [3,5-125I] diiodo-L-thyronine or [3,5-125I]-L-thyroxine.

Animals↗
PubMed1978

Uptake and metabolism of thyroid hormones by cultured monkey hepatocarcinoma cells. Effects of potassium cyanide and dinitrophenol.

Cultured monkey hepatocarcinoma cell (NCLP-6E) were used to investigate the uptake and metabolism of thyroid hormones. Intracellular accumulation was shown by the failure to acutely release hormone from cells subsequently exposed to serum proteins, and by the metabolic trnasformation of the hormones to deiodinated products and their sulfates. When hepatocarcinoma cell monolayers were studied at hormone concentrations below 10(-10) M, neither KCN nor dinitrophenol inhibited uptake. Taken together with previous findings that uptake was neither saturable nor reduced at low temperature, these results indicate that this process was not active transport. Deiodination of both the phenolic and non-phenolic rings, however, was partially inhibited by KCN but not by dinitrophenol. Sulfation of 3,3'-diiodothyronine and 3'-monoiodothyronine was strongly inhibited by both KCN and dinitrophenol. Uptake of the hormones and their metabolites was also measured in suspended hepatocarcinoma cells and compared with the uptake by normal rat hepatocytes, human fibroblasts and human lymphocytes. In these experiments 1 micrometer triidothyronine and 0.47 mM dinitrophenol were used to inhibit deiodination and sulfation, respectively. Uptake was similar in all cell types. Accumulation was highest with 3,5,3'-triiodothyronine, intermediate with other compounds having iodines in both rings, lowest with compounds iodinated in only one ring, and absent with iodothronine sulfates. These findings help to explain the relative rates of metabolism of the iodothyronines and their release from the cells.

Animals↗
PubMed1978

Thyroxine inactivation by starvation in cultured hepatocarcinoma cells, Formation of reverse triiodothyronine.

The effect of starvation on thyroid hormone metabolism was studied in monkey hepatocarcinoma monolayer cultures. Nonphenolic ring monodeiodination of thyroxine, 3, 5, 3'-triiodothyronine and 3, 3'-diiodothyronine was accelerated. Since phenolic ring deiodination of 3, 3',5'-triiodothyronine (reverse T3) was unaffected, this metabolite accumulated in the medium during thyroxine metabolism. This suggests that increased serum reverse T3 in malnourished humans may be caused by enhanced deiodination of thyroxine rather than decreased rT3 catabolism.

Animals↗
PubMed1978

The dissociation of b-TSH. The effect of sodium dodecyl sulfate, pH, urea and temperature.

In the present study SDS polyacrylamide gel electrophoresis was used to reinvestigate the conditions under which b-TSH dissociates into its constituent subunits. The effects of SDS, itself, urea, acid pH and temperature were assessed by the decrease in the amount of undissociated TSH and the increase in the dissociated components as revealed by SDS gel electrophoresis. In SDS alone 25--30% dissociation occurred. Pre-treatment with increasing concentrations of urea up to 7.1 M increased the degree of dissociation to 70% after h at room temperature. Maximum dissociation was achieved by treatment at pH 2.5 and 37 degree C for 1 h. In 1 M propionic acid approximately 10% of the TSH was still undissociated after 18 h at 25 degree C.

Animals↗