SPECIFIC RADIOIMMUNOASSAY OF CYCLO (HIS-PRO), A BIOLOGICALLY ACTIVE METABOLITE OF THYROTROPIN-RELEASING HORMONE

Abstract
We have developed a radioimmunoassay that can detect 10 pg cyclo (His-Pro) in rat brain perchloric acid extracts. The normal rat brain concentration of cyclo (His-Pro) ranged from 35–61 pmole/brain. The elution profiles of cyclo (His-Pro)-like immunoreactivity and radioactive cyclo (His-Pro) following gel filtration and ion-exchange chromatography were similar.