TRH-like immunoreactivity in rat pancreas and eye, bovine and sheep pineals, and human placenta: non-identify with synthetic Pyroglu-His-Pro-NH2 (TRH).

Extracts from albino rat eyes and pancreas, bovine and sheep pineals and human placenta containing TRH-like immunoreactivity were chromatographed on silica-gel plates. Comparison of elution profiles for TRH-like immunoreactivity with that of TRH revealed the presence of substances other than TRH in these samples. Chromatography of TRH-like immunoreactivity obtained from Rana pipiens skin eluted in two solvent systems produced elution profiles identical with that of synthetic Pyroglu-His-Pro-NH2 consistent with reports that frog skin contains large quantities of TRH. Implications of these findings are discussed.