CALCIUM ION DEPENDENCE OF THE 2-SITE IMMUNORADIOMETRIC ASSAY OF MOORE'S S-100 PROTEIN

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract— The two-site immunoradiometric assay (two-site IRMA) for a specific protein of the nervous system, S-100, is carried out by reaction of the S-100 protein solution with a solid-phase anti(S-100) followed by a second reaction in which the insoluble product is incubated with purified, radioactive anti(S-100). Unreacted labeled antibodies remain in solution and are washed away. As the amount of S-100 increases, the radioactivity in the solid-phase increases. The most significant assay variable is the effect of calcium on the assay dose-response. 0.1 mM-EDTA causes a total inhibition of the dose-response curve which is reversed by increasing the concentration of calcium ions. The dose-response reaches a maximum at 1.0mM-Ca2+. then becomes progressively inhibited as the Ca2+ concentration is increased further. Previous immunochemical studies of S-100 which did not allow for this effect must now be interpreted with caution.

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