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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #339130
Title: Testis composition and steroidogenic protein abundance in GnRH-II receptor knockdown boars

Author
item DESAULNIERS, AMY - University Of Nebraska
item CARREIRO, ELIZABETH - University Of Nebraska
item CEDERBERG, REBECCA - University Of Nebraska
item Lents, Clay
item WHITE, BRETT - University Of Nebraska

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/12/2017
Publication Date: 7/13/2017
Citation: Desaulniers, A.T., Carreiro, E.P., Cederberg, R.A., Lents, C.A., White, B.R. 2017. Testis composition and steroidogenic protein abundance in GnRH-II receptor knockdown boars. [Abstract] In: Society for the Study of Reproduction 50th Annual Meeting, Washington, DC, 13-16 July 2017. FT3.27, p. 41 (poster 496, p. 362). Available: www.ssr.org/17meeting.

Interpretive Summary:

Technical Abstract: Testosterone, secreted from Leydig cells, is classically stimulated by luteinizing hormone (LH) from the anterior pituitary gland, but an LH-independent mechanism of testosterone production has also been identified in the boar. Gonadotropin-releasing hormone II (GnRH-II) and its receptor (GnRHR-II) are abundant in porcine testes suggesting a prominent role in testis function. Immunostaining revealed that GnRHR-II localized to Leydig cells, and exogenous GnRH-II treatment stimulated testosterone release ex vivo. To further explore the role of GnRHR-II in the porcine testis, our laboratory produced a line of swine with reduced (70%) testicular GnRHR-II mRNA levels (GnRHR-II knockdown; KD). During pubertal development, transgenic boars tended to produce less testosterone, yet LH secretion was normal; levels were significantly impaired (82%) in adulthood. These data suggest that GnRH-II and its receptor directly modulate testosterone biosynthesis within porcine Leydig cells. However, the molecular link between GnRHR-II and testosterone output remains undefined. Therefore, the objectives of this study were to quantify testis composition and steroidogenic protein abundance in testicular tissue from GnRHR-II knockdown (n = 5) and littermate control (n = 4) boars. Testicular samples stained with hematoxylin and eosin were utilized to quantify Leydig cell area, Leydig cell number per field, interstitial and tubular area, average area of individual tubules and the number of tubules per field. Leydig cell area was greater in GnRHR-II KD (373.6 ± 20.4 µm2; P < 0.001) compared to littermate controls (316.3 ± 20.9 µm2). However, transgenic boars had fewer Leydig cells (9.8 ± 0.8 cells/field; P < 0.0001) than control boars (13.4 ± 0.9 cells/field) so interstitial area was similar (P > 0.05) between lines. The area of individual tubules was greater (P = 0.003; 71.6 ± 3.3 mm2) in transgenic compared to control animals (56.0 ± 3.7 mm2). However, the number of tubules per field was reduced (P = 0.0043) in transgenic compared to control boars (4.5 ± 0.2 tubules/field versus 5.5 ± 0.2 tubules/field) resulting in a similar (P > 0.05) total tubular area between lines. Immunoblotting was utilized to quantify steroidogenic protein abundance. Luteinizing hormone receptor levels were similar (P = 0.9834) between lines, suggesting that LH is not mediating the impaired testosterone secretion observed in transgenics. However, CYP11A1 was increased (P = 0.0317) 2-fold in GnRHR-II KD compared to littermate control boars. In addition, transgenic boars tended (P = 0.089) to produce 2-fold more CYP17A1 compared to littermate control boars. However, StAR and CYP19 levels were similar (P > 0.05) between lines. These data suggest that GnRHR-II KD boars exhibit compensatory mechanisms at both the cellular and protein level in a futile attempt to enhance testicular testosterone secretion. Partially supported by USDA/NIFA AFRI ELI predoctoral fellowship (2017-67011-26036; ATD), Hatch (NEB-26-199; BRW) and AFRI (2011-67015; CAL) funds.