A Second Antibody Solid Phase Enzyme Immunoassay for DexamethasoneYoshino,Nishiguchi

Abstract

A second antibody solid phase enzyme immunoassay for dexamethasone was established. Second antibody was immobilized onto microtiter plate by physical adsorption method. Second antibody immobilized plates were stable at least for one month at 4°. Anti-dexamethasone antiserum was obtained by immunizing rabbits with 4-(carboxymethylthio) dexamethasone-bovine serum albumin conjugate. Alkaline phosphatase, a labeling enzyme, was conjugated with 4-(carboxymethylthio) dexamethasone. Cross reactivity for cortisol which is considered as a candidate of interfering substance in serum with the antibody was 0.3%. Intraand inter-assay coefficients of variation for dexamethasone in human serum were 1.2-3.6% and 2.6-9.6%, respectively. Minimum amount of dexamethasone detected was 1.55pg/well and measurable range was 1.55pg-10ng/10μl serum. Chronological changes of serum dexamethasone in 4 normal subjects after an oral administration of 1mg of dexamethasone are also reported.