Use of Sodium Salicylate as a Blocking Agent for Cortisol-Binding-Globulin in a Radioimmunoassay for Cortisol on Unextracted Plasma

Abstract

This report describes investigations into the use of sodium salicylate as a cortisol-binding-globulin blocking agent and the subsequent development of a radioimmunoassay for cortisol on unextracted plasma. Cortisol antiserum was raised against a cortisol 3–0-(carboxymethyl) oxime-bovine serum albumin conjugate. A ¹²⁵I-labelled cortisol-tyrosine methyl ester conjugate was also prepared for use in the assay. The radioimmunoassay developed involved no pre-treatment or extraction of the samples before analysis and was extremely simple to perform. Comparison with another radioimmunoassay for cortisol and with the Mattingly fluorimetric assay gave good correlation.