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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Biosciences & Biotechnology Laboratory » Research » Publications at this Location » Publication #351994
Title: Differential pituitary response to GNRH and GNIH in low and high egg producing turkey hens

Author
item BRADY, KRISTEN - University Of Maryland
item Long, Julie
item PORTER, TOM - University Of Maryland

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/10/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Turkey hens with low egg production have a negative economic impact on the industry as these hens produce fewer poults yet cost the same to maintain as their high egg-producing counterparts. Egg production begins with the secretion of gonadotropin releasing hormone (GNRH) from the hypothalamus causing luteinizing hormone (LH) to be released from the pituitary. LH plays a role in triggering the ovulation of follicles from the ovary and thus is critical for egg formation in the hen's reproductive tract. LH also is negatively regulated by gonadotropin inhibitory hormone (GNIH) secretion from the hypothalamus. To determine if low egg-producing hens (LP) and high egg-producing hens (HP) respond differently to GNRH and GNIH, pituitaries from LP (n=3) and HP (n=3) hens were recovered post mortem, dissociated for cell culture and treated with GNRH or GNIH at a concentration of 0, 10-9, 10-8, or 10-7 M for 6 or 24 h. After incubation for 6 or 24 hours, cells were recovered from each treatment for RNA isolation. The mRNA levels of key receptors and the main targets of GNRH and GNIH action were assessed through reverse transcription-quantitative PCR. A two-way ANOVA, using the mixed models procedure of SAS, compared the normalized mRNA levels of pituitary cells from LP and HP among the basal and the three levels of both hormone treatments for each time point. In response to GNRH treatment for 6 h, cells from HP showed reduced gonadotropin inhibitory hormone receptor (GNIHR) expression relative to cells from LP (p<0.05). Pituitary cells from HP also upregulated the beta subunit of luteinizing hormone (LHB) mRNA after GNRH treatment for 6 and 24 h (p<0.05). In response to GNIH treatment, cells from HP showed increased gonadotropin releasing hormone receptor (GNRHR) expression after 6 h relative to cells from LP (p<0.05). Interestingly, pituitary cells from HP had increased LHB expression after 6 and 24 h of GNIH treatment (p<0.05). Cells from HP exhibited lower expression of GNIHR compared to cells from LP at basal conditions for each hormone and time point (p<0.05). At the transcript level, pituitary cells from LP and HP responded differently to GNRH and GNIH. Cells from HP up-regulated genes that were associated with ovulation stimulation; whereas cells from LP up-regulated genes that were associated with inhibition of ovulation. Differential pituitary cell response to GNRH and GNIH between LP and HP may play a role in the variation of egg production that occurs in the turkey industry.