Radioimmunoassay for 11-deoxycortisol using iodine-labeled tracer.

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Abstract
A simple and sensitive radioimmunoassay for 11-deoxycortisol was developed. The antiserum produced in rabbits by immunizing with a complex of 11-deoxycortisol-3-oxime and bovine serum albumin (BSA) has little cross-reactivity with other endogenous steroids. The immunoassay procedure requires only 1-step ethanol denaturation of binding proteins in plasma and extraction by an organic solvent can be omitted. Use of 125I-labeled tracer significantly simplify the counting procedure. The method is sensitive enough to detect 1 .mu.g/100 ml of 11-deoxycortisol. Plasma 11-deoxycortisol levels measured by this method after the administration of a single dose of metyrapone ranged from 5.0-19.2 .mu.g/100 ml, whereas they were 0-4.0 .mu.g/100 ml in hypopituitary patients. This simple method is useful for the routine assay of plasma 11-deoxycortisol as a parameter of the metyrapone tests.