Purification of thyrotropin from the pituitaries of two turtles: the green sea turtle and the snapping turtle.
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The purification of thyrotropin from the pituitaries of two species of turtles was followed using a bioassay based on the uptake of radioiodide by the thyroid of the baby slider turtle, Pseudemys scripta. Conventional chromatographic techniques which had previously resulted in the separation of pituitary gonadotropins were used initially, yielding a potent thyrotropin (TSH) from the snapping turtle (Chelydra serpentina) that was relatively free of gonadotropic activity. Several pituitary fractions high in thyrotropic activity were obtained from the sea turtle (Chelonia mydas), but all had significant gonadotropin contamination (primarily as luteinizing hormone, LH). Successful removal of this LH contamination was achieved by subjecting these glycoprotein preparations to countercurrent distribution, a technique which destroyed the gonadotropic activity while leaving the thyrotropic activity intact. Both species of turtle TSH resembled mammalian TSH in fractionation behavior. Additionally, the amino acid composition of the sea turtle TSH was strikingly similar to that of bovine TSH. Antisera raised against snapping turtle TSH, when used in conjunction with radiolabeled sea turtle TSH, allowed the development of a specific turtle thyrotropin radioimmunoassay able to detect blood levels of TSH in turtles treated with goitrogens. This represents the first successful purification of TSH from a nonmammalian tetrapod. 1981.