Follicle growth in the ovary of the rabbit after ovulation-inducing application of human chorionic gonadotropin

Abstract

The growth of tertiary follicles, i.e., the proliferation of cells in the stratum granulosum and in the capillary network of the theca interna, after injection of ovulation-inducing human chorionic gonadotropin (HCG), was investigated in the rabbit by means of autoradiographic and morphometric methods. Based on the frequency distribution of follicles with different sizes and on the labeling index (LI) of granulosa cells as a function of follicle size and of time prior to and after HCG stimulation, two groups of tertiary follicles can be distinguished: growing (250-900 micron in diameter) and mature (greater than 900 micron in diameter) elements. The growth of both groups is influenced by the release of gonadotropins. After HCG stimulation, follicles belonging to the first group grow rapidly. During, and a short time after ovulation, almost all non-ruptured follicles larger than 600 micron in diameter become atretic. Within 35-50 h the ruptured and atretic mature follicles (greater than 900 micron in diameter) are replaced by follicles out of the group of growing follicles. From these results the following concept for regulation of follicle growth is derived: In principle, all growing follicles possess the potential to develop into mature follicles. When a sufficient number of mature follicles is generated, these mature follicles determine the number of succeeding growing follicles. Follicles that are not required for providing mature follicles become atretic as soon as they reach a diameter of 700 micron. When the majority of mature follicles is lost during ovulation (by rupture or atresia), this inhibition regulated by mature follicles is abolished, and all of the growing follicles again are capable to develop into mature follicles. The relative amount of capillaries in the theca interna of growing and mature follicles remains constant with increasing follicle size. This means that the capillary network grows parallel to the increasing size of follicles. No differences are found between intact and atretic follicles; advanced atretic follicles were excluded from this study. The labeling index (LI) of granulosa cells in the stratum granulosum and of endothelial cells in the theca interna, as a function of follicle size and of time after HCG stimulation, are closely correlated. A change in the LI of granulosa cells is usually followed with a certain delay by a similar alteration of the LI of endothelial cells in the theca interna. This suggests that granulosa cells have a certain regulatory function on capillary growth.

Ovarian Structures During Sexual Receptivity at Mating and Post Coïtum Stage in Algerian Rabbits: A Comparative Study

“…The diameter of antral follicles equal to 640 μm is close to that obtained by Zitny et al (2004;682 μm) but less than that obtained by Kranzfelder et al (1984;800 μm). It appears that females of group R-+ AM + GnRH have antral follicles with a diameter greater than that of the other two groups.…”

“…Receptivity, measured by a test in the presence of a male or by observation of the color and turgescence of the vulva, reflects the state of oestrus or dioestrus of does (Moret, 1980).It has been indicated, that follicles > 1,8 mm were present only in receptive females (Lefevre & Caillol, 1978). In addition, works on themorphometric follicular studiesare often ancient (Kranzfelder et al, 1984), and on genetic types generally far removed from rabbit population sencountered in the Maghreb countries.…”

Morphological and Morphometric Analysis on the Rabbit Conjunctival Goblet Cells in Different Hormonal Conditions

“…In particular, the domestic female rabbit has a sexual cycle (Kranzfelder et al, 1984) based on the rhythmic growth of ovarian follicles, whose mean life is 7-10 days (Hill and White, 1933), which concomitantly inhibits other follicles to develop. After the ovulation, the inhibitory effect ends, so that other follicles are induced to begin maturation.…”

Buck effect on rabbit oestrous: vulva colour, vaginal lumen cells and ovarian follicle populations

“…In the absence of mating or hormonal stimulation, successive preantral follicles would become atretic and be reabsorbed into the ovarian cortex (Kranzfelder et al, 1984;Boiti, 2004;AriasAlvarez et al, 2010). Interestingly, spontaneous ovulation and pseudo-pregnancy in rabbits not mated or hormonally induced have been a puzzle for many years (Walton and Hammond, 1928;Templeton, 1940;Sawyer, 1959;Staples, 1967;Theau-Clément et al, 2000;Rebollar et al, 2008).…”