Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extra- and intracellular distribution of Prostatic Binding Protein (PBP) was studied in the different genital organs of the male rat by immunocytochemistry at the light and electron microscopic levels. PBP was extracted from cytosols of rat ventral prostate and used for immunization of rabbits. The specificity of the antiserum raised was tested by "western blotting" and immunoelectrophoresis. From the different fixatives tested for optimal structural and antigenic preservation of the ventral prostate a mixture containing 2.5% paraformaldehyde, 0.5% glutaraldehyde and 0.5% CaCl2 in cacodylate buffer, 0.05 M, pH 7.3 was selected. Using the immunofluorescence technique and the unlabeled antibody enzyme method PBP-immunoreactivity was detected at the light microscopic level in the luminal secretions of the ventral prostate. No reaction was observed with the seminal vesicle, the coagulating gland, the dorsal and lateral prostates, the epididymis and the testis. Intracellular secretory granules reacting with PBP antiserum were exclusively found in the secretory cells of the ventral prostate. Insufficiently fixed cells showed a diffuse generalized reaction of the cytoplasm indicating a leakage of the antigen from the secretory granules. Such artifacts were common in tissue sections processed with the preembedding-staining procedure. At the ultrastructural level therefore mostly the postembedding staining method was performed using both the unlabeled antibody enzyme method and the ferritin-labeled immunoglobulin technique in osmicated, Epon-embedded tissue. Labeling with either method was intense in the secretory granules and the condensing vacuoles, while the labeling density of the rough endoplasmic reticulum and the Golgi cisternae was in the background range. Castration experiments showed that secretory material displaying PBP immunoreactivity was retained within the acinar lumen of the gland for several days after castration, but was absent from most secretory cells already by four days after castration. Immunocytochemistry of PBP therefore is a very sensitive method for analysing the secretory activity and its androgen dependence of the prostate of the rat.
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PMID:Intracellular localization of Prostatic Binding Protein (PBP) in rat prostate by light and electron microscopic immunocytochemistry. 618 15

This study systematically examined the characteristics of specific binding of adult diferric transferrin to its receptor using a Triton X-100 solubilized preparation from human placentas as the receptor source. The following information was obtained. The ionic strength for maximal binding is in the range of 0.1-0.3 M NaCl. The pH optimum for specific binding extends over the range, from pH 6.0-10.0. Specific binding of diferric transferrin is not affected by 2.5 approximately 50 mM CaCl2 or by 10 mM EDTA. Triton X-100 in the concentration range of 0.02-3.0% does not affect specific binding. Specific binding is saturated within 10 min at 25 or 37 degrees C in the presence of excess amounts of diferric transferrin. The binding is reversible and the dissociation of diferric transferrin from the transferrin receptor is complete within 40 min at 25 degrees C. Apotransferrin, both adult and fetal, showed less binding than the holotransferrin species by competitive binding assay in the presence of 10 mM EDTA independent of up to 20 mM CaCl2. A 1500-fold molar excess of adult and fetal apotransferrin is required to give 40% inhibition for 125I-labeled diferric transferrin binding. Since calcium ion is not a factor, and since apotransferrin has such high binding affinity for iron (Ka = 1 X 10(24], this experiment suggests that the EDTA was necessary to prevent conversion of apotransferrin to holotransferrin from available iron in the reaction system. The specificity of the transferrin receptor for transferrin was examined by competitive binding studies in which 125I-diferric transferrin binding was measured in the presence of a series of other proteins. The proteins tested in the competitive binding studies were classified into three groups; in the first group were human serum albumin and ovalbumin; in the second group were proteins containing iron ions, such as hemoglobin, hemoglobin-haptoglobin complex, heme-hemopexin complex, ferritin, and diferric lactoferrin; in the third group were the metal-binding serum proteins, ceruloplasmin and metallothionein. None of these proteins except ferritin showed inhibition of diferric transferrin binding to the receptor. The effect of ferritin was small since a 700- to 1500-fold molar excess of ferritin is required for 50% inhibition of binding of diferric transferrin to the receptor.
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PMID:Characterization of transferrin binding and specificity of the placental transferrin receptor. 631 Nov 10

Non-transferrin-bound iron (NTBI) plays an important role in the hepatocellular injury induced by iron overload. However, the mechanism responsible for NTBI uptake into hepatocytes remains poorly defined. The purpose of this study was to define the kinetics of NTBI uptake by isolated rat hepatocytes and to characterize the uptake process. NTBI uptake was time and temperature dependent, exhibited a Michaelis-Menten constant (Km) value of 1.25 microM and maximum uptake of 241 pmol.10(6) cells-1.min-1, and 55Fe was incorporated in part into intracellular ferritin. Uptake was Ca2+ dependent, exhibiting 15 and 80% of maximal uptake in the presence of 0.6 and 0.75 mM CaCl2, respectively. The putative NTBI transporter was highly specific; divalent (Zn2+, Mn2+, Cd2+, and Co2+) or trivalent (La3+) cations did not inhibit Fe3+ uptake. Reduction from Fe3+ to Fe2+ was not essential for uptake or the process occurred deep within the membrane bilayer, since the Fe2+ chelator ferrozine did not influence 55Fe uptake. These data provide evidence for a low Km plasma membrane transporter for NTBI, which should be functional at physiological serum concentrations and saturated in iron-overload diseases, such as hemochromatosis.
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PMID:Evidence for a low Km transporter for non-transferrin-bound iron in isolated rat hepatocytes. 748 9

In vitro, when using low concentrations of ferritin (ng/ml) or CaCl2 (micrograms/ml), multiplication of a human, 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU)-resistant glioblastoma cell line (U251) is enhanced 1.5 to 2 times more actively than multiplication of a normal astrocyte line (CRL 1656). Ferritin and Ca2+ ions exhibit a marked effect on DNA isolated from these cells: glioblastoma DNA relaxation is strongly increased (as evidenced by increased 260 nm ultraviolet absorbance), being from 5 to 6 times that of astrocyte DNA, which remains only slightly affected. Under identical experimental conditions, Zn2+ and gallium ions selectively inhibit glioblastoma cell multiplication but at the same concentrations do not inhibit astrocyte multiplication. Ultraviolet absorbance measurements demonstrate that both of these agents condense relaxed glioblastoma DNA in vitro. Zn2+ or gallium ions added to culture medium containing stimulatory concentrations of ferritin or Ca2+ ions selectively and strongly inhibit enhancement of glioblastoma cell multiplication by these mitogens while not affecting normal multiplication of astrocytes.
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PMID:Differential effects of ferritin, calcium, zinc, and gallic acid on in vitro proliferation of human glioblastoma cells and normal astrocytes. 814 3

Major drawbacks to present-day cancer chemotherapy are its intrinsic lack of selectivity for tumour cells, resulting in severe damage to normal rapidly dividing cells, and the widespread emergence of drug resistance. Here experimental evidence is presented demonstrating that PB-100, a beta-carboline alkaloid, selectively inhibits in vitro multiplication of human BCNU-resistant glioblastoma cells (U251), but has no effect on normal astrocyte (CRL 1656) multiplication. PB-100 activity is dose-dependent. In the presence of ferritin or CaCl2, which are highly mitogenic for glioblastoma cells, higher doses of the alkaloid are required to inhibit multiplication completely. PB-100 is one of several compounds which were selected for their specific action on cancer DNA and cells, together with lack of activity on normal DNA and cells. Both the selectivity of PB-100 and its ability to overcome drug resistance stem from its effect on cancer DNA secondary structure. This activity is described and discussed, and therapeutic applications are mentioned.
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PMID:PB-100: a potent and selective inhibitor of human BCNU resistant glioblastoma cell multiplication. 829 50