Fasting Lowers Gastrin-Releasing Peptide and FSH mRNA in the Ovine Anterior Pituitary Gland

Authors

A. M. Fuller, University of Wyoming
K. J. Austin, University of Wyoming
A. J. Roberts, USDA-ARSFollow
G. E. Moss, University of WyomingFollow
B. M. Alexander, University of Wyoming

Date of this Version

2009

Citation

Published in Proceedings, Western Section, American Society of Animal Science (2009) 60: 275-277

Abstract

Estrogen receptor beta (ER-β), LH, and FSH are important mediators of reproduction. Follicle recruitment and development is stimulated by FSH. During anorexia, serum concentrations of FSH and LH decrease. Gastrin-releasing peptide (GRP), neuromedin B (NMB), peroxisome proliferator-activated receptorgamma coactivator 1 alpha (PGC-1α) and thyroidstimulating hormone (TSH) are important metabolic regulators expressed in the anterior pituitary gland (AP). Gastrin-releasing peptide stimulates release of ACTH, is associated with melanocortin in regulating food intake, and is a regulatory peptide in the female reproductive tract. In cattle, pituitary GRP expression was markedly up-regulated after resumption of estrus following parturition, indicating a connection between gene expression of GRP and reproductive function. The objective of this study was to determine effects of fasting during the luteal phase of the estrous cycle on gene expression in the anterior pituitary gland during the subsequent periovulatory period. Estrus was synchronized in mature (≥ 3 yr old) western white-faced ewes with prostaglandin F₂α (PGF₂α). Randomly selected ewes were fed grass hay ad libitum (control = 10) or were withheld from feed on days 7 – 11 of their estrous cycle (d 1 = estrus; fasted = 10). On d 12, fasted ewes were returned to feed and all ewes were treated with PGF₂α (0 hrs). Pituitaries were collected 72 h after PGF₂α. Ovaries were observed for presence of pre-ovulatory follicle or newly formed CL. Pituitaries were analyzed (n = 5 each group) from ewes that had ovulated. Fasting decreased (P < 0.05) gene expression of GRP and FSH. Differences in gene expression were not noted (P ≥ 0.26) in mRNA levels of PGC-1α, TSH, NMB, ER-β, or LH. Mediation of metabolic effects on reproductive function may be regulated by GRP affecting expression of FSH.