Response of hen pre-recruitment ovarian follicles to follicle stimulating hormone, in vivo

Kahina Ghanem; A L Johnson

doi:10.1016/j.ygcen.2018.10.004

Response of hen pre-recruitment ovarian follicles to follicle stimulating hormone, in vivo

Gen Comp Endocrinol. 2019 Jan 1:270:41-47. doi: 10.1016/j.ygcen.2018.10.004. Epub 2018 Oct 12.

Authors

Kahina Ghanem¹, A L Johnson²

Affiliations

¹ Interdisciplinary Program in Physiology, The Pennsylvania State University, University Park, PA 16802, USA; Department of Animal Science, The Pennsylvania State University, University Park, PA 16802, USA. Electronic address: kug163@psu.edu.
² Interdisciplinary Program in Physiology, The Pennsylvania State University, University Park, PA 16802, USA; Center for Reproductive Biology and Health, The Pennsylvania State University, University Park, PA 16802, USA; Department of Animal Science, The Pennsylvania State University, University Park, PA 16802, USA. Electronic address: alj14@psu.edu.

PMID: 30321534
DOI: 10.1016/j.ygcen.2018.10.004

Abstract

In laying hens, pre-recruitment ovarian follicles (1-8 mm diameter) are arranged as a continuum of size and predicted maturity. Cyclic recruitment of a pre-recruitment follicle to the preovulatory stage begins, in part, by the ability of the granulosa cell (GC) layer to initiate responsiveness to follicle stimulating hormone- (FSH-) induced cyclic adenosine monophosphate. The objective of this study was to determine if increased circulating concentrations of FSH during the ovulatory cycle increase the number of recruited follicles, in a dose-dependent manner. Equine chorionic gonadotropin (eCG) was initially tested due to its FSH-like properties and long half-life. Laying hens were injected, i.m., with 0 or 100 IU eCG, and ovaries were collected 29 h later. Recruited follicles were initially identified based on incorporation of yellow yolk and a weight of 250-900 mg. Recruitment was subsequently confirmed by both incubating the GC layer for 3 h with recombinant human (rh) FSH to establish FSH-responsiveness and quantifying P450 side-chain cleavage enzyme (CYP11A1) mRNA. Additional hens were injected with 0, 30, 75, and 300 IU eCG to establish a dose-response. Because eCG exhibits some luteinizing hormone activity, FSH-induced recruitment was evaluated by injecting 0.1, 0.33, 0.66, 1 or 3.3 µg rhFSH. Ovaries were collected 29 h post-injection, and expression of CYP11A1 mRNA was quantitated in GCs from recruited and pre-recruitment follicles. One hundred IU eCG induced recruitment of 2-8 follicles compared to a single follicle in control hens. In contrast to pre-recruitment follicles, incubated GC from eCG-recruited follicles had initiated differentiation, indicated by increased CYP11A1 and rhFSH-induced STAR mRNA and progesterone. Equine CG and rhFSH each increased the number of recruited follicles in a dose-dependent manner. Further, CYP11A1 mRNA was significantly increased in GC layers from recruited, compared to non-recruited, follicles. We conclude that FSH-responsiveness within the GC layer of each pre-recruitment follicle increases with follicle size, and propose that this establishes the order of daily follicle recruitment.

Keywords: Domestic hen; Follicle recruitment; Follicle stimulating hormone; Granulosa layer; Ovary.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Chickens
Female
Follicle Stimulating Hormone / metabolism*
Granulosa Cells / metabolism*
Humans
Ovarian Follicle / metabolism*

Substances

Follicle Stimulating Hormone