Enzyme-linked immunosorbent assay for the quantification of actinomycin D using beta-D-galactosidase as a label

An enzyme-linked immunosorbent assay (ELISA) for actinomycin D (AMD) has been developed, which allowed us to measure accurately as little as 50 pg of AMD per assay well. Anti-AMD sera was obtained by immunizing rabbits with an AMD derivative, 7-aminoactinomycin D (7AMD), conjugated with mercaptosuccinyl bovine serum albumin via N-maleoylaminobutyric acid chloride as a coupling agent. An enzyme marker was similarly prepared by coupling 7AMD with beta-D-galactosidase (EC 3.2.1.23) via N-maleoylaminobutyric acid. The ELISA with anti-AMD immunoglobulin G fraction as a solid phase and 7-aminoactino-mycin beta-D-galactosidase conjugate was specific to AMD as well as 7 AMD and showed 30% cross-reaction with actinomycin V, while no cross-reactivity was seen with drugs commonly used with AMD in combination chemotherapy for cancer treatment. The sensitivity of the ELISA was about 1000 times higher than high performance liquid chromatography in detecting AMD in lower concentrations. Using this assay, drug levels were easily measured in the blood and urine of rats following administration of AMD in a single dose of 0.25 mg/kg i.v. These results indicate that the ELISA provides a nonradioactive, inexpensive, sensitive, and rapid method applicable for pharmacological analyses of the drug.