Switching of follicle destiny so that the second largest follicle becomes dominant in monovulatory species.
Abstract: During an ovulatory follicular wave in the monovulatory species of heifers, mares, and women, the two largest follicles deviate in diameter at the end of a common follicle growth phase. The largest follicle before deviation becomes the future ovulatory follicle in most ovulatory waves. In 10-30% of the ovulatory waves, the destiny of the two follicles switches just before or at deviation so that the second-largest follicle becomes the future ovulatory follicle, and the largest follicle becomes a subordinate. In FSH-driven switching in heifers, mares, and women, the wave-stimulating FSH surge decreases to a low concentration before the largest follicle has developed the ability to utilize the low concentrations. The concentrations of FSH then increase (mares, women) or cease to decrease (heifers), and the next largest follicle acquires the capability of becoming the future ovulatory follicle. Luteolysis-driven switching has been reported in heifers but not in mares and women. The switching in heifers occurs during ovulatory wave 3 of three wave interovulatory intervals (IOI) when the wave of follicles is in the common growth phase in synchrony with the time of luteolysis. Regression of the CL during the common growth phase of ovulatory wave 3 is accompanied by decreased activity of follicles that are adjacent to the regressing CL but not when follicles and CL are separated or in opposite ovaries. The role of luteolysis in switching in heifers has been tested by treating with PGF2α when the largest follicle of wave 2 was near the end of the common growth phase. Switching in destiny of the largest follicle from the expected future dominant to a future subordinate occurred in most waves (10 of 17) when the largest follicle and regressing CL were in the same ovary and adjacent but not when separated in the same ovary or when in opposite ovaries (0 of 11). The newly selected future ovulatory follicle may develop in the opposite ovary. Thereby, frequency of the contralateral vs ipsilateral relationship between the preovulatory follicle and CL in heifers is greater in three-wave IOI than in two-wave IOI. In summary, the second largest predeviation follicle becomes the postdeviation dominant follicle when the decreasing FSH is out of phase with the largest predeviation follicle in heifers, mares, and women or when luteolysis and predeviation are in synchrony in heifers.
Copyright © 2021 Elsevier Inc. All rights reserved.
Publication Date: 2021-05-20 PubMed ID: 34058507DOI: 10.1016/j.theriogenology.2021.05.002Google Scholar: Lookup
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Summary
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This research examines the follicle development process in monovulatory species (specifically heifers, mares, and women). It presents findings that show, contrary to usual expectations, the second largest follicle can become the dominant or future ovulatory follicle, while the largest one can end up being a subordinate follicle. This switch in dominance is triggered by changes in FSH concentration and luteolysis.
Follicle Development and Destiny Determination
- During the process of ovulation, the two largest follicles experience a deviation in diameter growth, following a shared phase of follicle growth.
- The largest follicle generally becomes the ovulatory follicle in most cases. However, in 10-30% of cases, the roles switch so that the second largest follicle ends up being the ovulatory follicle while the largest one becomes subordinate.
Follicle Switching through FSH Concentration
- The phenomenon of follicle switching is driven by alterations in the concentrations of FSH (Follicle Stimulating Hormone).
- FSH concentration falls to low levels before the largest follicle has had the chance to utilise the decreased concentration. As a result, the follicle which is next in size acquires the potential to develop as the future ovulatory follicle.
Luteolysis-Driven Follicle Switching
- Such switching, triggered by the breakdown of the corpus luteum (luteolysis), has been observed in heifers but not in mares and women.
- In heifers, this switching takes place during the third wave of ovulatory activity, when luteolysis is happening and follicles are in their common growth phase.
- The regression of the corpus luteum during this phase results in decreased activity of follicles adjacent to the regressing structure but not when follicles and the corpus luteum are separate or in different ovaries.
Observation and Testing in Heifers
- Upon manipulating the course of luteolysis in heifers, it was noted that a follicle’s destiny tends to switch from being dominant to subordinate most commonly when the follicle and regressing corpus luteum are in the same ovary and located adjacent to one another. This switch did not occur when the two were separate within the same ovary or when they were in separate ovaries.
- The follicle that is newly selected to become the dominant one can develop in the opposite ovary. As a result, the frequency of cross-sided relations between the preovulatory follicle and the corpus luteum in heifers tends to be more common in the three-wave course of ovulation, as opposed to the two-wave sequence.
Cite This Article
APA
Ginther OJ.
(2021).
Switching of follicle destiny so that the second largest follicle becomes dominant in monovulatory species.
Theriogenology, 171, 147-154.
https://doi.org/10.1016/j.theriogenology.2021.05.002 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, WI, USA; Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: oj.ginther@wisc.edu.
MeSH Terms
- Animals
- Cattle
- Dinoprost
- Female
- Follicle Stimulating Hormone
- Horses
- Luteolysis
- Ovarian Follicle
- Ovary
- Ovulation
Citations
This article has been cited 3 times.- Perez-Guerra UH, Quispe YM, Gonzáles HI, Luque N, Ruelas DA, Carretero MI, Gutiérrez-Reinoso MA, Pérez-Durand MG, García-Herreros M. Ovarian Follicular Dynamics and Its Functional Significance in Relation with Follicle Deviation, Vaginal Cytology, and Hormone Profiles in Llamas (Lama glama).. Animals (Basel) 2022 Nov 25;12(23).
- López-Gatius F, Llobera-Balcells M, Palacín-Chauri RJ, Garcia-Ispierto I, Hunter RHF. Follicular Size Threshold for Ovulation Reassessed. Insights from Multiple Ovulating Dairy Cows.. Animals (Basel) 2022 Apr 28;12(9).
- Tanimoto R, Yoshida K, Ikeda S, Obata Y. Insights into in vivo follicle formation: a review of in vitro systems.. Histochem Cell Biol 2022 Mar;157(3):333-345.
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