Thyrotropin-releasing hormone in rat pituitary stalk blood and hypothalamus: Studies with high performance liquid chromatography

Abstract

Immunoreactive TRH (TRH-IR) in rat pituitary stalk blood and hypothalamus was investigated with high performance liquidchromatography in conjunction with a sensitive RIA. The TRH-IR of ethanol extracts of stalk blood resolved into three peaks, whether the blood was collected with the pituitary gland in situ or after the gland had been removed. The first peak corresponded to authentic TRH. By contrast, all the immunoreactive TRH in pituitary and hypothalamic extracts and in peripheral blood to which hypothalamic or syn-thetic TRH had been added eluted as a single peak with the same retention time as authentic TRH. The additional IR peaks in stalk blood did not correspond to known metabolites ..