A radioimmunoassay for N-acetylserotonin in biological tissues.

We have developed a specific radioimmunoassay for N-acetylserotonin. Cross-reactivity of 23 related or selected compounds is less than 1 percent; sensitivity is 10 to 25 picograms per tube; within assay coefficient of variation is 7.5 to 8.4%; and between assay coefficient of variation is from 7.1 to 11.1%. Satisfactory parallelism has been demonstrated for rat, hamster and rabbit serum, rat and hamster serum extract and rat brain retina and pineal extract. An extracted sample of rat serum gave one peak on HPLC which corresponded to authentic N-acetylserotonin. Daytime levels of N-acetylserotonin have been established for each of the tissues studied. This radioimmunoassay provides a sensitive and specific method for determination of N-acetylserotonin levels in biological tissues.