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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 #400689

Research Project: Improving Lifetime Productivity in Swine using Systems Biology and Precision Management Approaches

Location: Livestock Bio-Systems

Title: Diminished reproductive hormone concentrations in GnRHR-II knockdown gilts during the follicular phase of the estrous cycle may be attributed to reduced GnRHR-II levels in theca cells

item ROSS, CAITLIN - University Of Nebraska
item DESAULNIERS, AMY - University Of Nebraska
item CEDERBERG, REBECCA - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A
item CHOAT, FINA - University Of Nebraska
item ELSKEN, DOROTHY - University Of Nebraska
item KURZ, SCOTT - University Of Nebraska
item MILLS, GINGER - University Of Nebraska
item Lents, Clay
item WHITE, BRETT - University Of Nebraska

Submitted to: Molecular Reproduction and Development
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2023
Publication Date: 8/31/2023
Citation: Ross, C.E., Desaulniers, A.T., Cederberg, R.A., Choat, F.H., Elsken, D.H., Kurz, S.G., Mills, G.A., Lents, C.A., White, B.R. 2023. Diminished reproductive hormone concentrations in GnRHR-II knockdown gilts during the follicular phase of the estrous cycle may be attributed to reduced GnRHR-II levels in theca cells [abstract]. Molecular Reproduction and Development. 90(7):724.

Interpretive Summary:

Technical Abstract: Pigs are the only livestock species encoding a functional protein for both the second form of gonadotropin-releasing hormone (GnRH-II) and its cognate receptor (GnRHR-II). To examine the role of GnRH-II and its receptor in reproduction, we produced a swine line with reduced endogenous levels of GnRHR-II (GnRHR-II KD; Trans. Res., 26:567–575,2017). These gilts secreted 20% less serum 17ß-estradiol (E2) throughout the follicular phase of the estrous cycle compared with littermate controls. Further, peak E2 concentrations (-44 to -8h) before initiation of estrus (0 h) tended to be reduced in transgenics, despite similar serum gonadotropin concentrations. Therefore, the objectives of this study were to: (1) examine GnRH-II concentrations during peak E2 secretion and in follicular fluid (FF) of preovulatory follicles and (2) compare GnRHR-II levels in granulosa cells (GC) and theca cells (TC) from GnRHRII KD and littermate control gilts. To accomplish this, prepubertal animals (n=4 GnRHR-II KD and four control gilts) were monitored daily for behavioral estrus beginning at 180 days of age. Once all females exhibited a third behavioral estrus, they were individually fed altrenogest (15mg/day, 14 days) to synchronize estrus. Indwelling jugular catheters were surgically placed, and 48 h after altrenogest withdrawal, blood samples were collected every 4 h until 24 h following the onset of estrus (0 h). Serum GnRH-II concentrations were quantified with enzyme-linked immunosorbent assay (ELISA). Animals were euthanized during proestrus (Days 18–20) of the following estrous cycle. The FF, GC, and TC were isolated from preovulatory follicles for analysis with ELISA or immunoblotting. Statistical analyzes were performed using the MIXED procedure of SAS, fitting genetic line, and when appropriate, cell type, with the two way interaction. A Pearson correlation coefficient for hormone concentrations was determined using the CORR procedure of SAS. Concentrations of GnRH-II in FF did not differ between lines (p>0.05). However, 24 h before the onset of estrus, when peak E2 concentrations were reduced in transgenic versus control gilts (p<0.05), circulating GnRH-II levels were also diminished in GnRHR-II KD females (p<0.05). Thus, a strong positive correlation (p=0.82; p < 0.05) was detected between circulating concentrations of E2 and GnRH-II. Additionally, the presence of GnRHR-II in GC and TC was confirmed via immunoblotting. There was a line x cell type interaction for GnRHR-II protein abundance (p<0.05). The TC from GnRHR-II KD females expressed 40% less GnRHR-II protein than control TC (p = 0.06) or transgenic GC (p=0.08); no protein difference was observed for GC between lines (p>0.05). These data indicate that the interaction of GnRH-II with its receptor on porcine TC plays a crucial role in regulating steroidogenesis during the follicular phase of the estrous cycle. Supported by USDA/NIFA AFRI (2017-67015-26508) and Hatch Multistate (NEB-26-244) funds.