The Effect of Chelating Agents on Cellular Iron Metabolism

1976 ◽  
Vol 50 (3) ◽  
pp. 145-152 ◽  
Author(s):  
G. P. White ◽  
R. Bailey-Wood ◽  
A. Jacobs
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Iron Uptake ◽  
Chelating Agents ◽  
Iron Chelators ◽  
Gel Chromatography ◽  
Rhodotorulic Acid ◽  
Ferritin Synthesis ◽  
Chang Cell ◽  
Ferritin Iron

1. The effect of iron chelators on iron uptake, ferritin and total protein synthesis was studied in cultured Chang cells. Desferrioxamine depressed ferritin synthesis and completely inhibited iron uptake by ferritin protein. Rhodotorulic acid reduced iron uptake by the cells but had little effect on ferritin synthesis. Diethylenetriamine pentaacetic acid produced complete inhibition of iron uptake and all protein synthesis. 2,3-Dihydroxybenzoic acid (2,3-DHB) had no effect in this system. 2. When 2,3-DHB was incubated with a liver homogenate, its subsequent addition to a Chang cell culture resulted in depression of ferritin synthesis, iron uptake into the protein and some depression of total protein synthesis. Pretreatment of rhodotorulic acid did not affect its properties. 3. Non-ferritin iron in the Chang cell cytosol was dialysable, available for binding to transferrin and formed chelates which appeared, on gel chromatography, to be of low molecular weight. Gel chromatography of cytosol after incubation of the cells with chelating agents showed non-ferritin iron to be in a similar form. 4. Loss of non-ferritin iron from the cells occurred only when the transferrin in the medium was unsaturated. In the presence of chelating agents non-ferritin iron was lost from the cells even when transferrin was 100% saturated. 5. The results confirm the presence of an intracellular labile iron pool which is available for chelation, and demonstrate that different iron chelators have different metabolic effects.

scholarly journals The effect of chelating agents on iron mobilization in Chang cell cultures

Blood ◽  
1976 ◽  
Vol 48 (6) ◽  
pp. 923-929 ◽  
Author(s):  
GP White ◽  
A Jacobs ◽  
RW Grady ◽  
A Cerami
Keyword(s):  
Cell Cultures ◽  
Chelating Agents ◽  
Transferrin Saturation ◽  
Molar Ratio ◽  
Iron Release ◽  
Dihydroxybenzoic Acid ◽  
Equal Degree ◽  
Therapeutic Value ◽  
Chang Cell

Abstract The investigation of chelating agents with potential therapeutic value in patients with transfusional iron overload has been facilitated by the use of Chang cell cultures. These cells have been incubated with [59Fe]transferrin for 22 hr, following which most of the intracellular radioiron is found in the cytosol, distributed between a ferritin and a nonferritin form. Iron release from the cells depends on transferrin saturation in the medium, but when transferrin is 100% saturated, which normally does not allow iron release, desferrioxamine, 2,3- dihydroxybenzoic acid, rhodotorulic acid, cholythydroxamic acid, and tropolone all promote the mobilization of ferritin iron and its release from cells. They are effective to an approximately equal degree. The incubation of [59Fe]transferrin with tropolone in vitro at a molar ratio of 1:500 results in the transfer of most of the labeled iron to the chelator, reflecting the exceptionally high binding constant of this compound. How far these phenomena relate to therapeutic potentially remains to be seen.

Total protein content and protein synthesis within pre-elongation stage bovine embryos

1998 ◽  
Vol 50 (2) ◽  
pp. 139-145 ◽  
Author(s):  
J.G. Thompson ◽  
A.N.M. Sherman ◽  
N.W. Allen ◽  
L.T. McGowan ◽  
H.R. Tervit
Keyword(s):  
Protein Synthesis ◽  
Protein Content ◽  
Total Protein ◽  
Total Protein Content ◽  
Bovine Embryos

Effects of prolactin on testosterone-induced growth and protein synthesis in rat accessory sex glands

1983 ◽  
Vol 96 (3) ◽  
pp. 407-416 ◽  
Author(s):  
R. Jones ◽  
P. R. Riding ◽  
M. G. Parker
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Sodium Dodecyl ◽  
Chronic Administration ◽  
Specific Protein ◽  
Ventral Prostate ◽  
Plasma Prolactin ◽  
Accessory Sex Glands ◽  
Caput Epididymidis

The relative importance of testosterone and prolactin in regulating growth and protein synthesis in rat accessory sex glands has been investigated. Protein synthesis was measured by incubating tissue minces in vitro with [35S]methionine and analysing labelled proteins on polyacrylamide gels containing sodium dodecyl sulphate. Plasma prolactin was assayed by radioimmunoassay. Results showed that castration for 8 days significantly reduced wet weights and total protein synthesis in the ventral prostate, dorsolateral prostate and caput epididymidis, but that these effects could be reversed by exogenous testosterone. Similarly, the specific incorporation of [35S]methionine into four polypeptides in the ventral prostate, two polypeptides in the dorsolateral prostate and two polypeptides in the caput epididymidis was lowered by castration but markedly stimulated by testosterone. Acute or chronic administration of 2-bromo-α-ergocryptine to animals in combination with testosterone had no significant effect on any of the parameters measured, although the drug reduced circulating prolactin to undetectable levels. In addition, exogenous prolactin given alone, or in combination with testosterone, to hypophysectomized rats had no effect on general or specific protein synthesis. The induction of hyperprolactinaemia in immature or mature rats with pituitary homographs had no effect on testosterone-stimulated growth of any accessory gland, although it caused a significant stimulation of total protein synthesis in the dorsolateral prostate and coagulating glands. However, this was a generalized effect as it did not increase the specific incorporation of [35S]methionine into androgen-dependent proteins. The results do not indicate a major role for prolactin in regulating androgen responsiveness of male accessory sex glands in the rat.

scholarly journals Long-term modulation of type L pyruvate kinase activity in young and mature rats

1982 ◽  
Vol 204 (1) ◽  
pp. 329-338 ◽  
Author(s):  
Milinda E. James ◽  
James B. Blair
Keyword(s):  
Protein Synthesis ◽  
Pyruvate Kinase ◽  
Total Protein ◽  
Time Course ◽  
Enzyme Level ◽  
Enzyme Synthesis ◽  
Synthesis Rate ◽  
Adult Rats ◽  
Young Rats ◽  
Sucrose Diet

The regulation of type L pyruvate kinase concentrations in liver of young (35–45 days old) and adult (60–85 days old) rats starved and re-fed a 71% sucrose diet was investigated. Re-feeding is accompanied by an increase in the enzyme level in liver determined kinetically and immunologically. A constant ratio of kinetic activity to immunological activity was observed under all conditions examined, indicating that activity changes are the result of a regulation of synthesis or degradation and not an interconversion between kinetically active and inactive forms of the enzyme. Synthesis of pyruvate kinase was directly examined by using hepatocytes isolated from starved and re-fed rats. A stimulation of pyruvate kinase synthesis is observed on re-feeding. This increase in synthesis of pyruvate kinase is retained by the isolated hepatocyte for up to 7h in the absence of hormonal stimuli. Administration of glucagon (1μm) to the isolated hepatocytes had no influence on synthesis of pyruvate kinase and no evidence for a glucagon-directed degradation of the enzyme was found. Re-feeding the rat was followed by a transient increase in the synthesis of pyruvate kinase. The peak rate of synthesis was observed before a detectable increase in the enzyme concentration. After a rapid synthesis period, a new steady-state level of the enzyme was achieved and synthesis rates declined. The time course and magnitude for the response to the sucrose diet was dependent on the age of the rat. In young rats, an increase in pyruvate kinase synthesis is observed within 6h and peak synthesis occurs at 11h after re-feeding sucrose. The peak synthesis rate for pyruvate kinase for young rats represents approx. 1% of total protein synthesis. With adult rats, increased pyruvate kinase synthesis is not observed for 11h, with peak synthesis occurring at 24h after re-feeding. In the older rats, peak pyruvate kinase synthesis constitutes greater than 4% of total protein synthesis. Continued re-feeding of the adult rat beyond 24h is accompanied by a decline of pyruvate kinase synthesis to approx. 1.5% of total protein synthesis. The concentration of the enzyme, however, does not decline during this period, suggesting that control of pyruvate kinase degradation as well as synthesis occurs.

scholarly journals Effect of post-ischaemic recovery on albumin synthesis and relative amount of translatable albumin messenger RNA in rat liver

1982 ◽  
Vol 204 (1) ◽  
pp. 197-202 ◽  
Author(s):  
G Cairo ◽  
L Schiaffonati ◽  
M G Aletti ◽  
A Bernelli-Zazzera
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Messenger Rna ◽  
Relative Proportion ◽  
Liver Homogenate ◽  
Albumin Synthesis ◽  
Specific Proteins ◽  
Membrane Bound ◽  
Albumin Mrna

In liver cells recovering from reversible ischaemia, total protein synthesis by postmitochondrial supernatant and membrane-bound and free polyribosomes is not different from that in sham-operated controls. However, the relative proportion of specific proteins is changed, since the incorporation of [3H]leucine in vivo into liver albumin, relative to incorporation into total protein, as determined by precipitation of labelled albumin with the specific antibody, decreases by 40-50% in post-ischaemic livers. Cell-free synthesis by membrane-bound polyribosomes and poly(A)-enriched RNA isolated from unfractionated liver homogenate shows that the decrease in albumin synthesis in liver of rats recovering from ischaemia is due to the relative decrease in translatable albumin mRNA.

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