Gonadotrophic control of follicular development and function during the oestrous cycle of the ewe
- PMID: 6300383
Gonadotrophic control of follicular development and function during the oestrous cycle of the ewe
Abstract
In the adult non-pregnant ewe the secretion of FSH is sufficient to ensure a continuous growth and development of antral follicles to 3-5 mm size at all times. Further development and increased secretion of oestradiol through the final 72 h to ovulation depends on adequate stimulation by LH. During anoestrus and the luteal phase of the cycle LH pulses occur too infrequently to stimulate sufficient oestradiol to evoke an LH surge. Moreover, during the luteal phase progesterone secreted by the corpus luteum not only reduces the frequency of LH pulses but also inhibits the ability of oestrogen to evoke an LH surge. At the time of luteal regression the frequency of LH pulses increases to at least one per hour due to the fall in progesterone secretion. This change in pulse frequency of LH is associated with a decrease in the secretion of FSH, probably because of a direct inhibitory action of oestrogen on the anterior pituitary gland. The dominant follicle is probably relatively independent of circulating levels of FSH due to the high concentration of oestradiol and FSH within the microenvironment of the follicular cavity. Once the oestrogen secretion achieves a certain level a preovulatory surge of LH (and FSH) occurs. Increased sensitivity of the anterior pituitary to LH-RH and increased secretion of LH-RH from the hypothalamus both play a part in producing the LH surge. The rise in prolactin at this time probably reflects a decrease in hypothalamic dopamine turnover which is necessary for maximum release of LH-RH. The preovulatory LH surge initially stimulates and then totally inhibits further secretion of oestrogen and androgen from the ovulatory follicle. This suppression of steroid secretion is accompanied by a second peak of FSH at about the time of ovulation. The function of this second peak of FSH remains unknown although it may be responsible for the development of the large antral follicles which occur on Days 3 and 4. It is probably more important in those mammals like the rat and hamster which only form a functional corpus luteum if pregnancy occurs and in which oestrogen is necessary for implantation.
Similar articles
-
Physiology, Ovulation.2023 May 1. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. 2023 May 1. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 28723025 Free Books & Documents.
-
Endocrinologic control of normal canine ovarian function.Reprod Domest Anim. 2009 Jul;44 Suppl 2:3-15. doi: 10.1111/j.1439-0531.2009.01414.x. Reprod Domest Anim. 2009. PMID: 19754529 Review.
-
Temporal relations between plasma concentrations of luteinizing hormone, follicle-stimulating hormone, estradiol-17beta, progesterone, prolactin, and alpha-melanocyte-stimulating hormone during the follicular, ovulatory, and early luteal phase in the bitch.Theriogenology. 2006 Apr 15;65(7):1346-59. doi: 10.1016/j.theriogenology.2005.08.010. Epub 2005 Sep 28. Theriogenology. 2006. PMID: 16197989
-
Ovarian follicular and luteal physiology.Int Rev Physiol. 1980;22:117-201. Int Rev Physiol. 1980. PMID: 6248477 Review.
-
Inhibin and oestradiol in the control of FSH secretion in the sheep.J Reprod Fertil Suppl. 1991;43:125-38. J Reprod Fertil Suppl. 1991. PMID: 1843335 Review.
Cited by
-
Follicular and Hormonal Changes after Estrous Synchronization in Bottlenose Dolphins.Reprod Fertil. 2022 Sep 1;3(3):238-54. doi: 10.1530/RAF-22-0039. Online ahead of print. Reprod Fertil. 2022. PMID: 36074941 Free PMC article.
-
Bisphenol S Alters the Steroidome in the Preovulatory Follicle, Oviduct Fluid and Plasma in Ewes With Contrasted Metabolic Status.Front Endocrinol (Lausanne). 2022 May 24;13:892213. doi: 10.3389/fendo.2022.892213. eCollection 2022. Front Endocrinol (Lausanne). 2022. PMID: 35685208 Free PMC article.
-
Artificial Reproductive Technology (ART) Applied to Female Cervids Adapted from Domestic Ruminants.Animals (Basel). 2021 Oct 11;11(10):2933. doi: 10.3390/ani11102933. Animals (Basel). 2021. PMID: 34679954 Free PMC article. Review.
-
Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep.Animals (Basel). 2019 Apr 3;9(4):146. doi: 10.3390/ani9040146. Animals (Basel). 2019. PMID: 30987248 Free PMC article.
-
Neuroprotective Role of Steroidal Sex Hormones: An Overview.CNS Neurosci Ther. 2016 May;22(5):342-50. doi: 10.1111/cns.12538. Epub 2016 Mar 25. CNS Neurosci Ther. 2016. PMID: 27012165 Free PMC article. Review.