Radioimmunoassay of thyrotropin-releasing hormone (TRH) in rat, dog, and human blood.

A radioimmunoassay was developed for the measurement of exogenous thyrotropin-releasing hormone (TRH) in the whole blood of rats, beagle-dogs and humans. Even at low temperature, TRH is degraded so quickly in the whole blood that stabilization of TRH in the blood is necessary. For this purpose, the direct extraction with methanol and concentration before the radioimmunoassay was satisfactorily performed. The method is highly sensitive so that a lower quantifiable concentration of 20 pg/ml was detectable, and good reproducibility and standard errors of less than 10% from triplicate standard curves were obtained. At low concentration of TRH, the effect of food ingestion and volume of whole blood on the sensitivity of the radioimmunoassay was observed and thin layer chromatographic treatment improved it.