Radioreceptor assays specificity

Demonstration of Radioreceptor Assay Specificity Using Alternate Assays... 

The properties of membranes can also be used for analytical purposes. A radioreceptor assay for somatomalin A has been developed using human placental membrane. This assay is more sensitive and simpler than the chick bioassay and requires only 40 pi of serum. It is not species-specific... 

IGFs are measured in plasma or serum by a variety of methods including in vitro bioassay, radioreceptor assay, or immunoassay techniques.Most bioassays measure the sum of IGF-I and IGF-II bioactivity using rabbit chondrocytes, chick pelvic cartilage, or porcine rib cartilage." Such assays are relatively imprecise, insensitive, and often not specific. 

Binding Characteristics. For ligand-receptor binding assays, we used an EDTA/Tris-citrate (1 mM, pH 7.4)-dialyzed mitochondrial fraction of housefly heads, the so-called 2 fraction, which was prepared by a modification of Squires s method (4). The final pellet was frozen at -25°C and then suspended in 50 mM Tris-citrate buffer (pH 7.4 at 3°C) for assays. 4-w-Propyl[2,3-3h]-2,6,7-trioxa-l-phosphabicyclo[2.2.2]— octane 1-oxide ([ HjPr-BP, 41 Ci/mmol) was used as a ligand for the reason described above. Radioreceptor assays were performed by filtration techniques with glass fiber filters. Specific [ HjPr-BP binding was taken as that displaced by excess unlabeled Pr-BP(10 yM). 

SJ Capper, et al. Specificities compared for a radioreceptor assay and a radioimmunoassay of atrial natriuretic peptide. Clin Chem 36 656, 1990. 

Typical Standard Curve for ( H)-GABA Radioreceptor Assay Inhibition of Specifically Bound ( H)-GABA by Known Concentrations of Unlabeled GABA... 

Enna S. J and Snyder S. H (1976) A simple, sensitive and specific radioreceptor assay for endogenous GABA in brain tissue / Neurochem 26,221-224... 

If modifications in the receptor binding procedure are essential for developing a particular radioreceptor assay, then it is crucial that the receptor binding be redefined with regard to its kinetics and pharmacological specificity. Without such data, it is impossible to be certain that the appropriate receptor site is being labeled, which is a fundamental assumption for radioreceptor assays. 

The major drawback of radioreceptor assays relates to their specificity. While receptor binding assays are specific in that only a limited number... 

Exogenously administered substances are not the only agents which might interfere with a receptor binding assay. For example, opiate receptor binding as a radioreceptor assay for morphine would appear to be a relatively specific procedure since only opiates can interfere with the attachment to this receptor site. However, the discovery of endogenous opioid peptides makes the morphine assay less feasible with brain tissue because of the potential for these substances to be present in the tissue extracts. 

In order to demonstrate specificity, investigators have quantified samples using the radioreceptor assay and some other method of analysis, on the premise that if the values obtained are similar, then the radioreceptor assay is appropriate under the conditions employed. For example, the serum concentration of neuroleptics can be determined using a radioreceptor assay based on the dopamine receptor binding procedure (Creese and Snyder, 1977). To demonstrate the specificity of this assay, some samples were analyzed using both the radioreceptor assay and a radioimmunoassay (Table 3). The results obtained were virtually identical, indicating that the radioreceptor assay was measuring the same substance as that detected by radioimmunoassay. 

Enna, S. J., 19806, Radioreceptor assay a simple, sensitive, and specific analytical tool, in Receptor Binding Techniques (D. Bylund, ed.), pp. 257-271, Society for Neuroscience, Washington, D.C. 

Innis, R. B., Bylund, D. B., and Snyder, S. H., 1978, A simple, sensitive, and specific radioreceptor assay for P-adrenergic antagonist drugs. Life Sci. 23 2031-2038. 

Lesniak, M.A., Gorden, P., Roth, J., Gavin, J.R., III Binding of I-human growth hormone to specific receptors in human cultured lympho- 193. cytes. Characterization of the interaction and a sensitive radioreceptor assay. J. biol. Chem. 249, 1661-1667 (1974)... 

In the main this application deals with the analysis of plasma or semm for 25-OH-D3 and 1,25-(0H)2D3, two analytes which are present at low concentrations (25-OH-D3 1,25-(0H)2D3) in a relatively complex medium. It would appear at first sight that this presents a very difficult analytical challenge requiring the most extensive purification prior to quantitation. In the routine clinical laboratory, methods which are time-consuming and technically difficult are not as valuable as simpler and possibly, but not always, less specific methods. There is often a need in clinical situations for speed and simplicity and because of this, a considerable amount of development has taken place to produce simple and convenient assays in kit form, which depend upon the specificity of the saturation analysis quantitation procedure. The result is a method which couples solid-phase extraction with a radioreceptor assay which is both sensitive and specific. LC-MS meth-... 

Estimation of amino acid levels by radioreceptor binding techniques is a relatively new approach. The chapter on this topic reviews the underlying principles of ligand binding assays and details the practical considerations fundamental to the successful utilization of these techniques. Although this type of assay is extremely sensitive, it is beset with problems of specificity, and only one amino acid (GABA) can currently be determined accurately by the method Future developments should, however, extend its applicability to some of the other ammo acids, but it is likely to remain a method for determining a parhcular ammo acid, rather than one to be utilized for the measurement of a spectrum of ammo acids. 

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