Abundance of immunoreactive thyrotropin-releasing hormone-like material in the alfalfa plant.

Immunoreactive TRH (IR-TRH) is found in high concentrations (157 +/- 6 ng/g) in extracts of a plant, alfalfa. On high performance liquid chromatography (HPLC), most alfalfa TRH showed an increased retention time compared to synthetic TRH. Since the plant extract eluted after synthetic TRH on both Sephadex G-10 and Biogel P-2 chromatography, it does not appear to be an aggregate or a "big" TRH. Incubation with rat serum caused degradation of alfalfa TRH at a rate similar to synthetic TRH. Since the antibody against TRH is highly specific for the N and C terminal ends of the molecule, a point change at the His could explain the nature of alfalfa TRH. The biologic function of material resembling a mammalian hypothalamic releasing factor in this location is unknown, but its presence in the plant kingdom may have evolutionary significance.