A direct enzyme immunoassay for 18-hydroxycortisol in urine: a new tool for screening primary aldosteronism.

Abstract

A microplate enzyme immunoassay has been developed for the measurement of 18-hydroxycortisol in urine. An antiserum was produced by immunization of rabbits with a 3-O-(carboxymethyl)oximino-18-hydroxycortisol-bovine serum albumin conjugate. IgG was isolated from the antiserum and was biotinylated. Newly synthesized p-nitrophenyl ester of the oxime was used for the preparation of steroid-horseradish peroxidase conjugate. After an incubation of diluted urine samples (or standards) and the steroid-enzyme conjugate with the biotinylated antibody, the resulting antigen-antibody complex was separated by adding a portion of the reaction mixture into the avidin-coated microtiter plate. Peroxidase bound to solid phase was measured colorimetrically. The standard curve was linear from 0.25 to 10 ng/well. Intra- and interassay coefficients of variation were 5.5-8.8 and 7.8-8.2%, respectively. The assay was specific except for 18-hydroxycortisone with minor cross reaction. Urinary 18-hydroxycortisol excretion ranged 836-7460 and 26-696 nmol/24 h, respectively, in patients with primary aldosteronism (n = 8) and in control subjects (n = 40). This simple and rapid (< 4 h) assay is suitable for screening patients with primary aldosteronism.

• Authors: H Chiba, S Ikegawa, T Kurosawa, T Yoshimura, Y Ito, K Matsuno, K Kobayashi, M Tohma
• Journal: The Journal of steroid biochemistry and molecular biology (J Steroid Biochem Mol Biol) Vol. 46 Issue 1 Pg. 85-9 (Jul 1993) ISSN: 0960-0760 [Print] England
• PMID: 8338794 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Immunoglobulin G
• 18-hydroxycortisol
• Hydrocortisone

Topics

• Animals
• Antibody Specificity
• Humans
• Hydrocortisone (analogs & derivatives, urine)
• Hyperaldosteronism (diagnosis)
• Immunoenzyme Techniques
• Immunoglobulin G (isolation & purification)
• Predictive Value of Tests
• Rabbits