The TRH-like peptide pGLU-GLU-Pronh2 is present in the porcine pituitary but not in reproductive tissues

The peptide pGlu-Glu-ProNH2, which differs from thyrotrophin-releasing hormone (TRH) by only one amino acid, was initially detected and characterised in the rabbit prostate complex and more recently in human semen and rat pituitary. A previous study reported that TRH and a homologous peptide were present in a range of porcine tissues and it was of interest to further characterise these peptides. In this study, high levels of TRH-immunoreactivity have been demonstrated in the porcine pituitary, the majority of which was authentic TRH; although 9% was found to be chromatographically identical to pGlu-Glu-ProNH2. In contrast, TRH-immunoreactivity was not detected in follicular fluid, ovary or prostate. The unexpected finding that pGlu-Glu-ProNH2 is present in the porcine pituitary but absent from regions of the reproductive tract may be of biological significance.