Expression of luteinizing hormone-releasing hormone and its receptor in porcine immune tissues

Luteinizing hormone-releasing hormone (LHRH) is the primary regulator of pituitary LH release. However, LHRH has also been identified in extrahypothalamic sites including immune tissues. Accordingly, immunomodulatory properties for LHRH have been suggested. We wanted to determine whether LHRH and its receptor are produced by immune tissues in the pig. First, a cDNA was cloned and sequenced from the porcine hypothalamus that showed 87.5% homology with the human LHRH gene. Internal primers were identified from this sequence for amplifying a 268 bp product by PCR. In addition to the hypothalamus, PCR products reflecting LHRH mRNA were amplified in porcine spleen, thymus, and peripheral blood lymphocyte (PBL) cDNA. LHRH mRNA was not detected in liver, cerebral cortex, or pituitary tissue samples. Primers were designed to amplify a 360 bp fragment of LHRH-receptor cDNA. PCR products reflecting LHRH-receptor mRNA were amplified in pig hypothalamus, pituitary, thymus, spleen and PBL cDNA samples. No such products were amplified in cortex and liver samples. In summary, we report the sequence of a cDNA coding for LHRH and Gonadotropin-RH associated peptide (GAP) in the pig hypothalamus. Additionally, we provide evidence that LHRH and its receptor are synthesized in porcine immune tissues. This leads us to speculate that LHRH may have local, immunomodulatory functions in pigs.