A novel immunoradiometric assay for human liver ferritin.
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Rivanol, the cationic salt of an acridine base, has been used as a novel separation procedure in an immunoradiometric assay for human liver ferritin. The separation step is based on the differences in charge and molecular weight between the labelled antibody-ferritin complex and free labelled immunoglobulins. The resultant assay is simple, reproducible and sufficiently sensitive to determine serum concentrations of ferritin.Keywords:
Immunoradiometric assay
Human liver
Monoclonal antibodies to human α1-ietoprotein (AFP) have been compared with a conventionally produced antiserum using radioimmunoassay and two-site immunoradiometric techniques. A low-affinity antibody, which proved inadequate for use in a radioimmunoassay, gave asatisfactory dose-response Curve in a rapid two-site assay. A higher-affinity antibody yielded a simple, rapid, and sensitive two-site assay suitable for routine measurement of serum AFP.
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Two-site immunoradiometric assay for serum ferritin was developed by anti-human liver ferritin antiserum applied on polyvinyl V-bottom microtiter plates. The coefficient of variation was 4.4-5.9% of liver ferritin dissolved in 1/4 diluted human serum at a concentration of 0.625-125 ng/ml. The lowest concentration (0.625 ng/ml) was statistically distinguishable from the background by Student's t test (p < 0.05). Isoferritin patterns of serum ferritin and tissue ferritins were examined by the combination of gel isoelectric focussing and 2-site immunoradiometric assay in order to explore any similarities in pIs within these ferritins. Although serum ferritin had wide range of pIs, its basic isomers corresponded well to those of liver and spleen ferritin. Geometric means and their 95% confidence limits in serum ferritin concentration were 70 ng/ml and 12-411 ng/ml, respectively, in sera of 205 healthy males (16-25 years), and 12 ng/ml and 1-211 ng/ml, respectively, in 421 healthy females (16-59 years).
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Insulin-like growth-factor-binding proteins (BPs) in serum interfere with the measurement of insulin-like growth factor-I (IGF-I). Various assays have been developed to overcome this interference. We evaluated an immunoradiometric (IRMA) assay and compared it with the radioimmunoassay (RIA) using both native IGF-I and a truncated form of IGF-I [des (1–3) IGF-I] as radioligands. The IRMA was simpler (one step assay) and faster (3 hr incubation) than RIA(s) (overnight incubation). Sera were extracted with acid ethanol (AE) before all three assays. Analysis of serum samples (n = 78) performed by use of the two different radioligands in the RIA assays were highly correlated (r = 0.967, P < 0.0001). Measurements of serum IGF-I by IRMA in same samples were also highly correlated with those of the RIA assays (r = 0.952 for RIA and 0.947 for trIGF-I RIA, P < 0.0001 for both). To assess the effect of binding protein-3 (BP-3) levels (after AE extraction) on these assays, BP-3 levels were measured in sera from 36 healthy women. The mean BP-3 level was 3.6 ± 0.79 (S.D.) mg/L (range 1.3–5.0), and there was no significant difference in IGF-I levels measured by the three assays. Also, BP-3 levels were inversely correlated with IGF-I levels as measured by all three methods (r = 0.73 for IRMA, 0.71 for trIGF-I, and 0.75 for IGF-I RIA). To assess the effect of binding protein-1 (BP-1) levels on these assays, IGF-I was also measured by IRMA and trIGF-I RIA in 19 women with advanced breast cancer. Women with breast cancer had significantly higher (P < 0.001) BP-1 levels than age matched healthy women. IGF-I levels measured by IGF-I IRMA were slightly lower than those measured by trIGF-I RIA in breast cancer patients. However, this difference was not statistically significant (P = 0.56). These findings suggest that variations in BP-3 or BP-1 levels after AE extraction have no significant effect in any of these assays. We conclude that trIGF-I as a radioligand provides no added advantage over the standard IGF-I RIA. We also conclude that the IRMA assay is valid for measuring IGF-I and is faster and more convenient than RIA. © 1996 Wiley-Liss, Inc.
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Abstract The two‐site immunoradiometric assay for measurement of serum ferritin requires purified human ferritin and an avid high‐titer antihuman ferritin antibody. Some of the antibody is radioiodinated following purification by immunoadsorption. All methods for preparation of these materials for the assay are described in minute detail. Performance of the assay itself and calculation of results are also described, and attention is drawn to several potential pitfalls. Adherence to these detailed descriptions will help to eliminate difficulties experienced by centers wishing to establish their own working serum ferritin assay.
Immunoradiometric assay
Immunoadsorption
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DIRECT COMPARISON OF A RADIOIMMUNOASSAY AND AN IMMUNORADIOMETRIC TECHNIQUE IN THE MEASUREMENT OF HUMAN GROWTH HORMONE: PDF Only
Immunoradiometric assay
Human growth hormone
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Radioimmunoassays are simple and quite useful, being easily applied on a commercially serviceable basis. Furthermore radioimmunoassays are extremely sensitive and quite precise. Two site immunoradiometric assay in which one antibody was immobilized and another labelled with 125I becomes gradually popular, due to its higher sensitivity and the development of monoclonal antibody production by the hybridoma technique. Alternative analytical methods other than radioimmunoassays (radioimmunoassay, immunoradiometric assay) have been developed, in which the alternative labels to substitute for radioisotopes are enzymes, luminescent compounds and fluorescent probes.
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Abstract. The complex changes in serum LH and FSH levels from infancy to adulthood are diversely evaluated by radioimmunoassays or bioassays. The relative lack of sensitivity and specificity of radioimmunoassay, using polyclonal antibodies, could possibly be overcome by new immunoradiometric assays, using specific antibodies to LH and FSH. Significant differences were indeed observed between radioimmunoassays and immunoradiometric assays. During the prepubertal period, LH levels, measured by the immunoradiometric assays, were below the sensitivity of the method in the majority of the samples. LH levels were, however, well detectable when measured with radioimmunoassay, showing the heterogeneity of circulating LH structures. At the onset of puberty, LH levels increased at least 3 to 4 times in both sexes, when measured with immunoradiometric assays, whereas their increase was only 20 to 60% with the radioimmunoassays. FSH levels remained well detectable in the prepubertal period whether measured by immunoradiometric or radioimmunoassays. At pubertal onset, FSH increase in both sexes was more important in the immunoradiometric assays. The results obtained with immunoradiometric assays give a better insight into the quantitative and qualitative function of the gonadotropes during childhood. The almost complete absence of LH during the prepubertal period and the steep increase at the onset of puberty better reflects the reported data obtained with bioassays. The persistance of significant levels of FSH in the prepubertal ages, and the lesser increase at the onset of puberty, when compared with LH, illustrates that the individual regulation of LH and FSH secretion vary over time and is influenced by developmental factors.
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