STUDIES ON THE NATURE OF MAMMALIAN HYPOTHALAMIC THYROTROPHIN RELEASING HORMONE USING IMMUNOCHEMICAL, CHROMATOGRAPHIC AND ENZYMIC TECHNIQUES

Hypothalamic extracts from three mammalian species (rat, rabbit and sheep) were found to contain several ng of immunoreactive thyrotrophin releasing hormone (TRH)-like activity. This substance chromatographed on ion exchange chromatography (carboxymethyl cellulose) as a single peak that was indistinguishable from synthetic TRH. Hypothalamic TRH was also inactivated by normal human plasma at a rate (1.21-1.46%/mul plasma/h and 1.59-1.77%/50mul plasma/min) similar to that of synthetic TRH (1.42%/mul plasma/h and 1.73%/50mul plasma/min). This combination of chromatographic and enzymic techniques can be applied to the identification of immunoreactive TRH in body fluids.