Lents Clay A, Thorson Jennifer F, Desaulniers Amy T, White Brett R
United States Department of Agriculture, Agricultural Research Service, U. S. Meat Animal Research Center, Clay Center, Nebraska.
University of Nebraska-Lincoln, Department of Animal Science, Lincoln, Nebraska.
Mol Reprod Dev. 2017 Sep;84(9):994-1003. doi: 10.1002/mrd.22830. Epub 2017 Jun 21.
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.
在养猪业中广泛使用人工授精每年需要数百万剂公猪精液。公猪的生育力低下仍然是一个主要限制因素，这可能会影响数千头母猪的繁殖效率，因此需要更好地了解睾丸功能，以便开发提高精液产量的方法。考虑到这一点，本文综述了RF酰胺相关肽3（RFRP3）和促性腺激素释放激素II（GnRH-II）对猪促性腺激素分泌和睾丸功能的影响。RFRP3的受体存在于猪的下丘脑、腺垂体和睾丸中。体外研究的证据表明，RFRP3可能通过抑制下丘脑GnRH-I和垂体促黄体生成素（LH）的分泌而成为猪的促垂体激素；然而，RFRP3对猪体内LH分泌的影响很小。在猪睾丸内，RFRP3通过抑制类固醇生成酶来抑制睾酮分泌。GnRH-II及其受体（GnRHR-II）在猪睾丸中大量存在。间质细胞表达GnRHR-II，尽管LH分泌极少，但外源性GnRH-II能强烈刺激公猪睾酮分泌。数据表明，GnRH-II直接刺激成熟公猪睾丸分泌睾酮。因此，RFRP3和GnRH-II在公猪中的主要功能似乎分别是对睾丸内睾酮分泌的自分泌-旁分泌抑制和刺激。更好地了解睾丸在发育过程中RFRP3和GnRH-II系统的变化，将为如何改善公猪睾丸功能提供重要线索。
