Acetic acid extracts of hypothalamic tissue of bovine origin were concentrated by a precipitation procedure and subjected to gel filtration on Sephadex. Thyrotropic hormone-releasing factor (TRF) activity was followed by measuring the release of thyrotropic hormone (TSH) from rat pituitary tissue in vitro, the release of 131I in mice pretreated with codeine and thyroxine as well as the elevation of plasma TSH in thyroidectomized rats pretreated with thyroxine. TRF activity was consistently found to emerge from Sephadex just after α- MSH and before arginine vasopressin. The TRF zone from Sephadex was further greatly purified by phenol extraction and then subjected to chromatography on carboxymethylcellulose (CMC). TRF area from CMC was repurified by rechromatography. Purified TRF was active in vivo at the level of 10 μg and in vitro at the dose of 1 μg. Chemical and biological characteristics indicate that TRF is a weakly basic polypeptide different from oxytocin, vasopressin, α- and β- MSH and LRF. (Endocrinology78: 726, 1966)
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Schally et al. (1966) studied this question.