Τόμος 2 (1984) – Τεύχος 3 – Άρθρο 3 – Επιθεώρηση Κλινικής Φαρμακολογίας και Φαρμακοκινητικής-Ελληνική Έκδοση – Volume 2 (1984) – Issue 3 – Article 3 – Epitheorese Klinikes Farmakologias και Farmakokinetikes-Greek Edition

2: 199-210 (1984)

PHARMAKON-Press: Epitheorese Klin. Farmakol. Farmakokinet.

2: 199-210 (1984)

Radioimmunoassay

Radioimmunoassay (RIA) has been developed during the last twenty five years and is being widely used for the assay of clinically significant compounds, such as hor­mones, vitamins, drugs etc. Radioimmunoassay belongs to the group of the ligand assays. Like all the assays of this group, radioimmunoassay methods are based on the binding (reaction) of two compounds: the antigen (ligand), which is usually the compound to be determined, and the antibody (binder). The determination of an antigen using a RIA method is based on the competition between the “cold” and the “hot” antigen for the occupation of a restricked num­ber of binding sites of the specific antibody. The unknown antigen concentration is deter­mined by comparison. To do this, the inhibition that a series of known concentrations of the antigen (standard solutions) induce on the binding of the labeled antigen to the specific antibody is compared with the extent to which this same binding is inhibited by the unknown concentration of the antigen (unknown sample). In all the cases the quantities of antibody and labeled antigen are constant, the tracer being in excess of antibody. A reference standard curve is being used for this comparison. The basic principle of radioimmunoassay analysis can be expressed in a more general form. Given an unvarying quantity of antibody (bin­der) of fixed Κ value, the ratio of bound to free antigen (ligand) at equilibrium will be quanti­tatively related to the total amount of antigen (ligand) present. This is the basic principle of all ligand assays. The main characteristic and the great advantage of radioimmunoassay is its high sensitivity, specificity and simplicity. This explains its greatly extended use during the last years in the field of medical, biochemical and pharmacological research as well as in routine estimation either as exclusive method or as the method of choice for the determina­tion of biologically active compounds of high significance.

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