Location: Reproduction ResearchTitle: RFamide-related peptide 3 and gonadotropin-releasing hormone-II are autocrine-paracrine regulators of testicular function in the boar Author
Submitted to: Molecular Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2017
Publication Date: 9/1/2017
Citation: Lents, C.A., Thorson, J., Desaulniers, A.T., White, B.R. 2017. RFamide-related peptide 3 and gonadotropin-releasing hormone-II are autocrine-paracrine regulators of testicular function in the boar. Molecular Reproduction and Development. 84:994-1003. https://doi.org/10.1002/mrd.22830. Interpretive Summary: The wide-spread use of artificial insemination in the swine industry requires over 30 million doses of semen each year. Consequently, the impact of a single subfertile boar reaches thousands of females. This highlights a critical need to gain a greater understanding of testicular function in boars in order to develop methods to improve semen production and quality. ARS Scientists at Clay Center, Nebraska, and scientists at the University of Nebraska, Lincoln, studied two different hormones called RFamide-related peptide 3 (RFRP3) and gonadotropin-releasing hormone-II (GnRH-II). They found receptors for these hormones in the testes of boars. Receptors were on specialized cells called Leydig cells that produce testosterone. Testosterone is required for spermatogenesis and libido in boars. Scientists found that RFRP3 suppressed testosterone, whereas GnRH-II stimulated testosterone. Receptors for these hormones were also found on sperm cells, suggesting that these hormones could be important for spermatogenesis or fertility of semen. Scientists are using this information to better understand how to improve semen production and quality in pigs.
Technical Abstract: Widespread use of artificial insemination in swine requires millions of doses of boar semen each year. Subfertility of boars remains a major constraint, which can impact the reproductive efficiency of thousands of sows, so a better understanding of testicular function is needed in order to develop methods to improve semen production. With this in mind, the effects of RFamide-related peptide 3 (RFRP3) and Gonadotropin-releasing hormone-II (GnRH-II) on gonadotropin secretion and testicular function of pigs are reviewed here. Receptors for RFRP3 are present in the pig hypothalamus, adenohypophysis, and testis. Evidence from in vitro studies indicates that RFRP3 could be a hypophysiotropic hormone in the pig by suppressing secretion of GnRH-I from the hypothalamus and luteinizing hormone (LH) from the pituitary gland; however, effects of RFRP3 on in vivo secretion of LH in pigs are minimal. Within the pig testis, RFRP3 suppresses testosterone secretion by inhibiting steroidogenic enzymes. GnRH-II and its receptor (GnRHR-II) are abundant in pig testes. Interstitial cells express GnRHR-II, and exogenous GnRH-II robustly stimulates secretion of testosterone in boars, despite minimal secretion of LH. Data illustrate that GnRH-II directly stimulates secretion of testosterone from the testes of mature boars. Thus, the primary function of RFRP3 and GnRH-II in the boar appears to be autocrine–paracrine inhibition and stimulation, respectively, of testosterone secretion within the testis. A better understanding of changes in the RFRP3 and GnRH-II systems within the testis during development will provide important clues about how to improve the testicular function of boars.