Young Scholar Presentation: Primary Hypogonadism in Gonadotropin-Releasing Hormone II Receptor Knockdown Boars

• Published in: Journal of animal science 2018-04, Vol.96, p.52-53
• Main Authors: Desaulniers, A T, Cederberg, R A, Knox, R V, Lents, C A, White, B R
• Format: Article
• Language: English
• Subjects: Adults; Animal reproduction; Artificial insemination; Cannulae; Chorionic gonadotropin; Diurnal; Euthanasia; Fertility; Gonadotropin-releasing hormone; Gonadotropins; Hogs; Hormones; Hypogonadism; Leydig cells; Livestock; Luteinizing hormone; Males; Mass spectrometry; Mass spectroscopy; mRNA; Pituitary (anterior); Pulse duration; Regulators; Reproduction (biology); Secretion; Semen; Sex hormones; Steroidogenesis; Steroids; Swine; Testes; Testosterone
• ISSN: 0021-8812; 1525-3163

Paradoxically, the second mammalian GnRH isoform (GnRH-II) and its receptor (GnRHR-II) are not phys...iological regulators of gonadotropin secretion. Instead, our data suggests that both are abundantly produced in the porcine testis and mediate testosterone secretion, independent of luteinizing hormone (LH). To further study the role of this system, our laboratory generated a knockdown (KD) swine line with 70% lower testicu...lar GnRHR-II mRNA levels compared with littermate controls. During pubertal development, testosterone concentrations tended to be reduced in transgenic versus littermate control boars (P < 0.06), yet LH concentra...tions were unaffected (P > 0.10). In adults, the diurnal secretory patterns of testosterone and basal circulating concentrations of 9 other gonadal steroids were evalu...ated using animals fit with indwelling jugular cannulae. Testosterone concentrations were constitutively reduced in GnRHR-II KD compared with littermate control boars (P < 0.05). Pulse analysis indicated that trans...genic boars tended to produce fewer pulses of testoster...one than littermate controls (P < 0.10). Amplitude of pulses was reduced in transgenic boars (P < 0.05) but pulse duration was unaffected (P > 0.10). GnRHR-II KD boars also tended to have lower minimum and max...imum concentrations of testosterone (P < 0.10). Mass spectrometry revealed that gonadal steroids were dra...matically impacted by GnRHR-II KD; concentrations of steroids derived from the testis were either signifi...cantly decreased (7 hormones) or tended to be reduced (3 hormones) in transgenic boars. Next, the sensitiv...ity of GnRHR-II KD and littermate control boars to GnRH analogues was assessed. Transgenic males pro...duced less testosterone (P < 0.05) in response to treat...ment with a GnRHR antagonist (SB-75), known to bind GnRHR-II. Compared with littermate control boars, transgenic males were also less responsive to GnRH-II and human chorionic gonadotropin (P < 0.05). In order to determine if reduced testosterone secretion affected semen quality, ejaculates were subjected to computer-assisted semen analysis. Both sperm motility and the number of artificial insemination doses produced per ejaculate tended to be reduced in GnRHR-II KD boars (P < 0.10). At euthanasia, transgenic boars tended to have smaller testes than littermate controls (P < 0.10) and produced less testosterone per gram of testicular tissue (P < 0.05). Ultimately, these data demonstrate that GnRH-II and