1. Response of hen pre-recruitment ovarian follicles to follicle stimulating hormone, in vivo
- Author
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Kahina Ghanem and Alan L. Johnson
- Subjects
endocrine system ,food.ingredient ,Granulosa cell ,030209 endocrinology & metabolism ,Biology ,Andrology ,03 medical and health sciences ,Follicle-stimulating hormone ,chemistry.chemical_compound ,Follicle ,0302 clinical medicine ,Endocrinology ,food ,Ovarian Follicle ,Yolk ,Animals ,Humans ,Cyclic adenosine monophosphate ,Equine chorionic gonadotropin ,030304 developmental biology ,0303 health sciences ,Granulosa Cells ,Cholesterol side-chain cleavage enzyme ,chemistry ,Female ,Animal Science and Zoology ,Follicle Stimulating Hormone ,Luteinizing hormone ,Chickens - 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.
- Published
- 2019