Identification of the human seminal TRH-like peptide pGlu-Phe-Pro-NH2 in normal human prostate

Human and rat prostate contain thyrotropin-releasing hormone immunoreactivity (iTRH) including TRH and an uncharged TRH-like peptide. Recently the uncharged TRH-like peptide pGlu-Phe-Pro-NH2 was purified from human semen. To determine whether this peptide was of prostatic origin, human and rat prostate extracts were analyzed by ion-exchange chromatography and reversed-phase HPLC. The predominant uncharged iTRH comigrated exactly with synthetic pGlu-Phe-Pro-NH2 on HPLC and had identical affinity to pGlu-Phe-Pro-NH2 in a TRH radioimmunoassay. We conclude that prostate is a source of this peptide in humans and rats. This amidated TRH-like peptide may play a role in human reproductive physiology.