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PubMed1980

[Transferrin, somatomedins and growth].

Plasma transferrin is significantly positively correlated to the growth velocity in normal children and children with various growth disorders. In hypopituitary dwarfs, both plasma transferrin and somatomedin are significantly lower than in controls. Acute variations of the plasma transferrin levels could be involved in the regulation of the GH secretion by a feedback mechanism. Yet, transferrin is neither a somatomedin or a somatomedin-binding protein, and the mechanisms relating growth to transferrin remain unknown.

Adolescent↗

PubMed1984

[Mapping of the transferrin gene in laboratory rats, mice and man by direct in situ hybridization].

Mapping of the gene coding for transferrin was carried out in metaphase chromosomes from bone marrow of laboratory mice and rats as well as from PHA-stimulated human lymphocytes using direct in situ hybridization technique. Plasmid pRTf-17 carrying the insert of rat transferrin cDNA was nick-translated with [125I]dCTP and used as a specific hybridization probe. The total number of silver grains and their distribution along differentially stained chromosomes were determined in 464 metaphase plates (114, 263 and 87 from rat, mouse and man, respectively). The data obtained enable us to assign transferrin gene to chromosome 3 in human and chromosome 9 in mouse. For the first time, the rat transferrin gene was localized on chromosome 7. The most probable sites of transferrin gene localization are 7q31-34, 9F1-3 and 3q21 in rat, mouse and human chromosomes, respectively.

Animals↗

PubMed1978

Serum erythropoietin measurements using the fetal mouse liver cell culture: the importance of reduction of variation in the specific activity of radioiron--transferrin.

Because of varying iron--transferrin concentrations in different serum samples, and varying test serum portions within the culture, variations of the radioiron--transferrin/total iron--transferrin ratio are inevitable, when serum erythropoietin (Ep) concentrations are measured using the fetal mouse liver cell assay. It could be demonstrated that radioiron uptake is directly proportional to the specific activity of radioiron--transferrin, when the latter varies over the range which is inherent to the method. Variations of the ratio of radioiron--transferrin/total iron--transferrin were reduced by preincubating radioiron with human transferrin, and by minimizing the test serum portion of the culture. With this modified in vitro bioassay, serum Ep concentrations of 59 healthy subjects were measured. Mean serum Ep concentration was 136 +/- 66 (s.d.) mU/ml.

Animals↗

PubMed1984

[Genetic polymorphism of transferrins in Bovinae].

Variability of transferrins in Bovinae is controlled by two loci: Tf (the locus of structural transferrin gene) and T (the locus of a gene responsible for protein modification). Originally, the ancestors of Bovinae, like the other ruminants, had the R type of transferrin (T-/T- genotype, inactive T gene). Later on, the T gene activation occurred and the B type appeared (T+/T-, T+/T+ genotypes). The subsequent evolution of Bovinae was accompanied by almost complete fixation of T+ allele. In one of the Bovinae representatives (Bos taurus L.) the frequency of T- allele remained at the level of approx 0.1. A hypothesis is proposed which explains the change of the transferrin type in Bovinae by imitation of multiple allelic forms of this protein present in Tf heterozygotes, by supplementary modificatory multiple transferrin forms arising on activation of the minor gene (T+). This process is assumed to involve the reduction of Tf locus variability. Since this hypothesis proceeds from the assumption of TF heterozygote advantage, the question is considered, whether this assumption is compatible with high polymorphism of Tf locus which significantly exceeds that for other loci.

Alleles↗

PubMedDate not supplied

[Transferrin in various hematological syndrome].

In 100 patients with various haematological syndromes and in 22 healthy subjects serum transferrin was determined by the method of radial immunodiffusion of Mancini. The results were correlated with total iron-binding capacity, iron concentration, beta1 globulin and albumin levels. A statistically significant rise in serum transferrin concentration was demonstrated only in patients with sideropenic anaemia. In the remaining groups of patients transferrin concentration was decreased without regard to associated disturbances of iron metabolism and iron level. The comparison of the total iron-binding capacity with transferrin level determined by radial immunodiffusion may suggest presence of iron-binding proteins other than transferrin.

Anemia, Hemolytic↗

PubMedDate not supplied

[Isolation of transferrin and albumin from Cohn fraction IV of human blood plasma proteins].

To isolate transferrin and additional amounts of albumin the parameters are developed for subfractionating with the alcohol-rivanol method fraction IV (according to Cohn) of plasma proteins (waste of albumin production from plasma of donor blood). The suggested method for fraction IV subfractionating makes it possible to obtain true albumin and transferrin. In all series the yield of wet and dry sediments of transferrin is constant. To remove alcohol from albumin and transferrin half-finished products the regimes of sublimation drying are worked out at which protein is not denaturated. Albumin obtained from fraction IV satisfies all the requirements of MPTY-42 N 3500-67 for the albumin preparation from donor blood. The developed method for subfractioning fraction IV of plasma proteins is easily reproduced on an industrial scale, permits a 8% increase in albumin yield from 1 1 of plasma and a simultaneous obtaining of transferrin which may be a basis for medicinal preparation.

Humans↗

PubMed1982

Lactoferrin and transferrin in bovine milk in relation to certain physiological and pathological factors.

Mean transferrin and lactoferrin concentrations in whey samples from 376 uninfected quarters of 42 Holstein X Friesian cows on the 30th, 150th and 270th days of lactation were respectively 0.030 and 0.080 mg/ml. The mean transferrin concentration in serum was 4.63 mg/ml. Lactation number and location of quarters did not influence milk lactoferrin and transferrin values. Lactoferrin concentration increased significantly (P less than 0.01) in uninfected quarters from 0.03 to 0.06 and to 0.15 mg/ml on the three successive sampling times. Transferrin whey concentration increased significantly (P less than 0.01) only in late lactation, from 0.025 (30th and 150th days of lactation) to 0.035 mg/ml (270th day of lactation). Lactoferrin concentration increased significantly (P less than 0.01) in quarters infected by major pathogens (41 samples) whereas minor pathogen infections (61 samples) caused no significant increase. The correlation coefficients between milk lactoferrin and transferrin concentrations and somatic cell-count were 0.42 and 0.65 respectively.

Age Factors↗

PubMed1981

Transferrin binding and iron uptake by mouse lymph node cells during transformation in response to concanavalin A.

Mouse lymph node cells cultured with Concanavalin A (Con A) in serum-free medium containing 59Fe-transferrin took up 59Fe more rapidly than cells cultured without Con-A. Uptake of iron commenced rapidly and preceded the onset of DNA synthesis in stimulated cells. Total uptake of transferrin during culture was much lower than that of iron, indicating that cells could remove iron from transferrin. The released transferrin appeared to be undergraded. Lymphoblasts bound six times more transferrin per cell than small lymphocytes. Lymphocytes also took up iron from citrate and nitrilotriacetate complexes, and iron so acquired was not readily removed by desferrioxamine, indicating that it was not bound extracellularly.

Animals↗

PubMed1995

Molecular characterization of an insect transferrin and its selective incorporation into eggs during oogenesis.

A protein with a molecular mass of 65 kDa that was specifically taken up into eggs was purified from the hemolymph of adult female Sarcophaga peregrina flies. From cDNA analysis, this protein was shown to be a Sarcophaga transferrin. Unlike mammalian transferrin, the similarity between its N-terminal and C-terminal halves was only 19%, and it was suggested to conjugate one iron atom/molecule in its N-terminal half. Sarcophaga transferrin was found to transport iron ions into eggs during oogenesis and deliver them to another protein, thought to be ferritin. No significant activation of the transferrin gene was detected during embryogenesis, so probably maternal transferrin is used as an intercellular or intracellular iron-transporter during embryogenesis of this insect.

Amino Acid Sequence↗

PubMed1994

Expression and characterization of recombinant human eosinophil-derived neurotoxin and eosinophil-derived neurotoxin-anti-transferrin receptor sFv.

The gene for the human recombinant eosinophil-derived neurotoxin (rEDN) was synthesized and fused to the gene encoding a single chain antibody (sFv) to the human transferrin receptor (EDNsFv). Both rEDN and EDNsFv were expressed as insoluble proteins in inclusion bodies in Escherichia coli BL21(DE3). Following denaturation and renaturation, EDN and EDNsFv were partially purified by chromatography on heparin-Sepharose. Final purification of EDN was achieved by Sephadex G-100, whereas EDNsFv which contained a 6-histidyl residue carboxyl terminus was highly purified using the metal chelate resin, Ni(2+)-nitriloacetic acid. Whereas the recombinant EDN had ribonuclease activity that was similar to the native protein, the fusion protein had enzymatic activity that was 6-13% that of native EDN. The fusion protein was able to bind to the human transferrin receptor. In contrast to rEDN that had no inherent cytotoxicity to human tumor cells, the EDNsFv fusion protein was cytotoxic to human leukemia cells that express the human transferrin receptor with an IC50, 0.2-1 nM. At 1.3 nM EDNsFv, no cytotoxicity was observed on cells that lack the human transferrin receptor. Free antibody to the human transferrin receptor, E6, inhibited the cytotoxicity of the EDNsFv. Human enzymes may be engineered to acquire cytotoxic properties by fusing them to antibodies. Thus, they may be candidates for the construction of immunofusion proteins that may be less immunogenic than immunotoxins containing bacterial- or plant-derived toxin moieties.

3T3 Cells↗

PubMed1994

ESAG 6 and 7 products of Trypanosoma brucei form a transferrin binding protein complex.

In Trypanosoma brucei, the gene for the expressed variant surface glycoprotein (VSG) is preceded by a series of open reading frames designated expression site associated genes (ESAGs), which together with the VSG gene form a polycistronic transcription unit. It is shown that the products derived from two ESAGs (ESAG 6 and 7 in the nomenclature of Pays, E., et al. Cell 57, 835-845 (1989)) form a complex, which binds transferrin with high affinity. Transferrin affinity chromatography yields heterodimers or higher order heteroligomers composed of the products of ESAG 6 and ESAG 7. The former is a heterogeneously glycosylated protein of 50 to 60 kDa modified by a glycosylphosphatidylinositol membrane anchor at the COOH-terminus, while the latter is the previously identified 42 kDa glycoprotein carrying an unmodified COOH-terminus (Schell, D., et al. EMBO J. 10, 1061-1066 (1991) and Schell, D., et al. EMBO J. 12, 2990 (1993)). When isolated from trypanosomes grown in rodents, the complex is in part free and in part associated with transferrin. Also, the complex is present both in the membrane fraction and the soluble fraction of cell lysates. As shown by immunoelectron microscopy, both transferrin and ESAG 6/7-derived proteins can be demonstrated in the lumen of the flagellar pocket, an invagination of the plasma membrane serving as the sole site for endocytotic uptake of macromolecular nutrients. Weak labeling is also obtained on the flagellar pocket membrane and in intracellular vesicles. The possibility that the binding protein complex serves as a receptor for the uptake of transferrin in T. brucei is discussed.

Amino Acid Sequence↗

PubMed1994

[Carbohydrate-deficient transferrin--a reliable marker of high alcohol consumption?].

Carbohydrate deficient transferrin has been proposed as an important marker for alcohol abuse. Using isoelectric focusing and two different radioimmunoassays we measured carbohydrate deficient transferrin throughout an alcohol withdrawal period in ten abusing men. Values within the normal range were found in two to four individuals, depending on the method. Nevertheless, carbohydrate deficient transferrin was more frequent pathologically (in two out of three methods) than any other of the common markers (glutamyl transferase, alanine transferase, aspartate transferase, mean corpuscular volume). During the withdrawal period, the carbohydrate deficient transferrin value increased in two patients after a new alcohol intake. However, it also increased on other occasions when a new alcohol intake was highly unlikely. Therefore, a single test or even repeated tests of carbohydrate deficient transferrin may give a wrong conclusion. Since the cost of the analysis is high, the clinical benefit should be evaluated more closely before the test is used in pure clinical settings.

Adult↗

PubMed1975

The synergistic binding of anions and Fe3+ by transferrin. Implications for the interlocking sites hypothesis.

The finding that transferrin does not bind Fe3+ at the specific metal binding sites in the absence of carbonate and synergistic anions emphasizes the fundamental importance of the anion binding site to the chemistry of Fe3+-transferrin-CO32-. An important question regards the chemical and structural requirements for carbonate substitution. This has been, however, an area of some dispute in the literature. We have utilized four synthetic routes for the preparation of Fe3+-transferrin-anion complexes. The products have been examined with regard to spectral properties, and reaction with: (a) NaHCO3, (b) Fe3+-nitrilotriacetic acid in NaHCO3, and (c) sodium citrate under CO2-free conditions. The results provide information as to which anions are synergistic, and the basic properties of the Fe3+-transferrin-anion complexes that are formed. The 6 inorganic anions that were tested were all found to be nonsynergistic. Dihydroxyacetone and glyceraldehyde were also nonsynergistic. Dicarboxylic acids were found to form stable Fe3+-transferrin-anion complexes which were only slowly displaced by carbonate. Several monocarboxylic acids with proximal aldehyde, ketone, alcohol, amino, or thiol functional groups proved to be synergistic. CPK molecular model studies suggested the functional group and the carboxylic acid must be able to fit within a site between 6.3 and 7.0 A in maximal length. One large substituent could be accommodated by the site, however, two methylgroups on the alpha carbon to a carboxylate group could not be accommodated. Chloroacetate and monocarboxylic acids were nonsynergistic. The results are interpreted in terms of an interlocking sites hypothesis which envisions the synergistic anion as interacting with the protein via its its carboxyl group and bonding with the Fe3+ via its proximal functional group.

Alcohols↗

PubMed1993

The expression of transferrin mRNA in the salivary glands and other tissues of baboons.

In order to determine whether all the extrinsic salivary glands synthesize transferrin mRNA, the polyadenylated ribonucleic acids [poly(A)+ RNAs] from parotid, submandibular, and sublingual glands, liver, midbrain, testis, spleen, heart, kidney, and the mucosae of oesophagus and stomach from adult male baboons were analysed, using oligo(dT)-cellulose chromatography, agarose gel electrophoresis, followed by transfer of the mRNAs to nitrocellulose filters and identification with transferrin and tubulin cDNA probes. Transferrin and tubulin mRNAs were visualized by autoradiography and analysed by measuring specific activity from beta emitting nuclides following transfer to nitrocellulose filters and hybridizing with [alpha-32P]-labelled human transferrin and tubulin cDNA probes. The results indicate that transferrin mRNA is present in all the extrinsic salivary glands (submandibular, sublingual, parotid) of baboons.

Animals↗

PubMed1993

Characterization and quantitation of the circulating forms of serum transferrin receptor using domain-specific antibodies.

To characterize the nature of the immunoreactive transferrin receptor in human serum, antisera were developed to peptide sequences of the extracellular domain of human transferrin receptor between amino acids 107 and 120 and the intracellular domain between amino acids 40 and 54. Antisera against the extracellular domain exhibited reactivity against both purified intact receptor and immunopurified circulating receptor, whereas antisera against the intracellular domain reacted only with intact receptor. Using competitive binding enzyme-linked immunosorbent assays, transferrin receptor in ultracentrifuged sera from normal subjects and patients with sickle cell anemia could be detected with antisera against the extracellular but not the intracellular domain. When the pellet obtained by ultracentrifugation of these sera was assayed after solubilization in 1% teric (polyoxyethylene-9-lauryl ether), only 0.6% of total serum receptor was detected in normal subjects and 3.8% in subjects with sickle cell disease. Roughly equal amounts of this pelleted immunoactivity were detected with antibodies against the extracellular and intracellular domains. These results indicate that less than 1% of transferrin receptor in normal human sera is intact receptor consistent with an exosomal origin and that virtually all circulating transferrin receptor is in the form of a truncated extracellular domain.

Amino Acid Sequence↗

PubMed1995

Correlation of beta-2 transferrin and middle ear abnormalities in congenital perilymphatic fistula.

Congenital perilymphatic fistula (PLF) as a diagnosis for progressive, fluctuating, or sudden sensorineural hearing loss with or without vertigo is still controversial. Beta-2 transferrin is a protein that is unique to cerebrospinal fluid, aqueous humor, and perilymph. A recent pilot study demonstrated that beta-2 transferrin may be an objective test to determine the existence of a congenital PLF. The authors prospectively evaluated and recommended surgery for 43 children with suspected PLF over the past 3 years. A prospective, blinded study was performed by having the attending otolaryngologist evaluate the middle ear at the time of surgery for a PLF and any middle ear abnormalities. Samples of fluid were collected from the oval and round windows and were tested for beta-2 transferrin. Of 16 patients undergoing tympanoplasty or tympanomastoidectomy who served as controls, none were positive for beta-2 transferrin. Of the 43 patients undergoing exploratory tympanoplasty for PLF, 20 (46.5%) were considered to be negative for PLF on microscopic visualization; 23 (53.5%) were found to be positive. Of the 20 patients thought to be negative for PLF, 18 (90%) tested negative for beta-2, but 2 of these patients were positive for beta-2, and both had a congenital middle ear abnormality. Of the 23 patients found to have a PLF at surgery, 6 (26.1%) tested positive for beta-2, and all of these 6 had middle ear abnormalities. Of the 17 patients negative for beta-2, 9 had normal anatomy; 6 had middle ear abnormalities, and 2 had erosive changes. The authors conclude that beta-2 transferrin, an objective test, confirms the existence of congenital PLF in children, which is associated with middle ear abnormalities.

Adolescent↗

PubMed1996

Iron transport across Caco-2 cell monolayers. Effect of transferrin, lactoferrin and nitric oxide.

Differentiated Caco-2 colon carcinoma cell monolayers grown in bicameral chambers have been used as an in vitro model to study the effect of different carrier molecules on mucosal iron transport. Transfer of iron across the monolayers in the apical-to-basolateral direction was greater from ferric lactoferrin than from iron citrate, while very little transport occurred from Fe-transferrin. However, a greater proportion of iron was retained by the cells when Fe-citrate was the donor. Caco-2 cells expressed transferrin receptors (n = 1.3 x 10(5) /cell; Ka = 2 x 10(8) l/mol), but binding of lactoferrin, though substantial in quantity, had an affinity too low to measure. When monolayers were incubated with 125I-labelled lactoferrin or transferrin some 125I-activity was transported, but almost all was TCA-soluble, suggesting that degradation products rather than intact protein were being transported. Addition of 10 microM S-nitroso-N-acetyl-D,L-penicillamine (SNAP), which produces nitric oxide (NO) in solution, caused a significant increase in iron transport from ferric citrate, but not from Fe-lactoferrin or Fe-transferrin. It is concluded that in this in vitro system lactoferrin but not transferrin enhances mucosal iron transport, and that NO may play a regulatory role in iron absorption.

Biological Transport↗

PubMed1996

Nephelometric determination of carbohydrate deficient transferrin.

We describe a technique for measuring carbohydrate-deficient transferrin (CDT) in serum. Serum transferrin fractions are separated by anion-exchange chromatography on microcolumns. Sialic acid-deficient transferrin fractions are collected in the eluate, and transferrin is then quantified by a rate-nephelometric technique. Imprecision (CV) was 4-5% within-run and 7-9% between runs (n = 15). Comparison with an isoelectric focusing-immunofixation method for transferrin index (x) yielded y = 761x + 7, Sy/x = 39 mg/L. Assay of sera from 90 abstainers or moderate consumers of alcohol showed that 81 (90%) had CDT concentrations between 30 and 70 mg/L. Among 74 alcoholics admitted to an alcohol treatment center, 54 (73%) had CDT > 70 mg/L, i.e., the diagnostic sensitivity was 73% at a specificity of 90% (area under receiver-operator characteristic curve = 0.891).

Adolescent↗