Evidence for gonadotropin-releasing hormone peptides in the ovary and testis of rainbow trout

GnRH is usually classified as a neuropeptide that is synthesized in the bra in. Recent evidence indicates that GnRH mRNA is present also in the ovary a nd testis. However, isolation of the peptide from testis has not been repor ted. We used HPLC and specific RIAs to determine whether the GnRH peptide c an be detected in gonads, the developmental stage at which the peptide is e xpressed, and the number of molecular forms of GnRH that are present in the ovary and testis. Extracts of immature and mature ovarian and testicular t issue were examined from 17- to 21-mo-old rainbow trout (Oncorhynchus mykis s). For the first time, GnRH peptides were isolated from testis and identified by HPLC-RIA with specific antisera and by elution position compared with sy nthetic standards. GnRH peptides were also present in the ovary, In additio n, multiple forms of GnRH, including a form not normally detected in the br ain of trout, were shown to be present in the gonads. During development, G nRH peptides were expressed only at specific stages in the gonads, which ma y explain the inability to detect and isolate the GnRH peptides from gonads in earlier studies.