Abstract
A simple and specific enzyme immunoassay for betamethasone was developed. In order to improve the specificity and affinity of antibodies for betamethasone, the antiserum was prepared by immunizing rabbits with a 4-(carboxymethylthio) betamethasone-bovine serum albumin conjugate. Alkaline phosphatase was used as a labeling enzyme. Cross reactivity for cortisol which is considered as a candidate for the interfering substance in serum with the antibody was 0.03%. Intra-and inter-assay coefficient of variations were 4.1-8.3% (n=6) and 3.1-13.7% (n=6), respectively. The minimum amount of betamethasone detected was 1 pg/tube and the measurable range was from 0.1 to 100ng/ml, using 10μl of serum sample without extraction. The chronological changes of serum betamethasone and cortisol concentration in five normal subjects after an oral administration of 1 mg of betamethasone were also reported.
