Radioimmmunoassay for melatonin in human serum.

Goat antisera raised against N-acetyl-5-methoxytryptophan conjugated to bovine thyroglobulin by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is utilized in a radioimmunoassay for melatonin. The raised antibodies are coupled to Sepharose 4B and melatonin in human serum is isolated by affinity chromatography, thereby avoiding the time-consuming extractions by organic solvents. A detection limit of 1.9 pg (8.2 X 10(-15) mol) melatonin is achieved. The antibody specificity has been analysed and none of the common melatonin analogues influence this method of melatonin measurement.