Location: Reproduction ResearchTitle: Gonadotropin-releasing hormone II receptor (GnRHR-II) knockdown reduces testis size and decreases testosterone secretion during pubertal development in swine Author
|Desaulniers, Amy - University Of Nebraska|
|Cederberg, Rebecca - University Of Nebraska|
|Mills, Ginger - University Of Nebraska|
|White, Brett - University Of Nebraska|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 12/22/2015
Publication Date: 3/1/2016
Citation: Desaulniers, A.T., Cederberg, R.A., Mills, G.A., Lents, C.A., White, B.R. 2016. Gonadotropin-releasing hormone II receptor (GnRHR-II) knockdown reduces testis size and decreases testosterone secretion during pubertal development in swine [abstract]. Journal of Animal Science. 94(Supplement 2):149 (Abstract #327).
Technical Abstract: The second mammalian isoform of gonadotropin-releasing hormone (GnRH-II) functions quite differently from the classical form (GnRH-I) as it is a poor stimulator of gonadotropin release. Unlike most species, a functional GnRHR-II has been identified in swine. Our laboratory detected GnRHR-IIs on Leydig cells and demonstrated that GnRH-II stimulates testosterone release as effectively as GnRH-I, despite minimal luteinizing hormone (LH) secretion. These data suggest that GnRH-II acts directly on Leydig cells to stimulate steroidogenesis. Therefore, we produced a knockdown (KD) swine line to further examine the function of GnRHR-II. Here, the objective was to evaluate testis size and serum hormone levels in transgenic males during pubertal development. GnRHR-II KD (n = 7) boars and littermate controls (n = 5) were monitored throughout development; blood was collected and testis size measured using calipers at 40, 100, 150, 190, 225 and 300 d of age. Predicted testis volume was calculated and serum was isolated for testosterone and LH radioimmunoassay. For testis volume, we observed an effect of line (P = 0.0006), time (P < 0.0001) and a tendency for a line by time interaction (P = 0.0731). By 300 d of age, testes from transgenics were smaller than littermate controls (559.9 ± 34.3 versus 772.6 ± 39.7 cm3; P < 0.05) despite similar body weights (P > 0.05). We also observed an effect of line (P < 0.0001), time (P < 0.0001) and a line by time interaction (P = 0.0018) for serum testosterone concentrations. Testosterone levels were similar (P > 0.05) between lines from 40-100 d of age but lower in transgenic boars at 150 (1.3 ± 0.9 versus 3.7 ± 1.0 ng/ml), 225 (6.9 ± 1.5 versus 15.2 ± 1.5 ng/ml) and 300 (12.2 ± 1.5 versus 21.3 ± 1.5 ng/ml) d of age. Notably, LH levels were similar (P = 0.91) between transgenic (0.34 ± 0.08 ng/ml) and littermate controls (0.32 ± 0.09 ng/ml) at 300 d of age, suggesting that LH is not mediating the diminished testosterone secretion observed in transgenics. Together these data indicate that in swine, GnRHR-II is involved in LH-independent steroidogenesis and postnatal testicular development. Partially supported by NIFA Hatch (NEB-26-199; BRW) and AFRI (2011-67015; CAL) funds.