Equine chorionic gonadotropin alters luteal cell morphologic features related to progesterone synthesis

Abstract

Exogenous eCG for stimulation of a single dominant follicle or for superovulation are common strategies to improve reproductive efficiency by increasing pregnancy rates and embryo production, respectively. Morphofunctional changes in the CL of eCG-treated cattle include increases in CL volume and plasma progesterone concentrations. Therefore, we tested the hypothesis that eCG alters the content of luteal cells and mitochondria related to hormone production. Twelve crossbred beef cows were synchronized and then allocated into three groups (four cows per group) and received no further treatment (control) or were given eCG either before or after follicular deviation (superovulation and stimulation of the dominant follicle, respectively). Six days after ovulation, cows were slaughtered and CL collected for morphohistologic and ultrastructural analysis. Mitochondrial volume per CL was highest in superovulated followed by stimulated and then control cows (18,500 ± 2630, 12,300 ± 2640, and 7670 ± 3400 μm(3); P < 0.001), and the density of spherical mitochondria and the total number of large luteal cells were increased (P < 0.05) in stimulated cows compared with the other two groups (110.32 ± 14.22, 72.26 ± 8.77, and 70.46 ± 9.58 mitochondria per μm(3) and 678 ± 147, 245 ± 199, and 346 ± 38 × 10(6) cells, respectively. However, the largest diameters of the large luteal cells were increased in superovulated and control cows versus stimulated ones (32.32 ± 0.06, 31.59 ± 0.81, and 29.44 ± 0.77 μm; P < 0.0001). In contrast, the total number of small luteal cells was increased in superovulated cows (1456 ± 268, 492 ± 181, and 822 ± 461 × 10(6), P < 0.05). In conclusion, there were indications of cellular changes related to increased hormonal production (stimulatory treatment) and increased CL volume (superovulatory treatment).

Aromatase inhibitor treatment with an intravaginal device and its effect on pre-ovulatory ovarian follicles in a bovine model

“…Treatment with letrozole may have resulted in an increase in luteal cell numbers or an alteration in the proportion of small and large luteal cells within the CL and an increase in progesterone-producing capability per CL volume. In this regard, treatment of cows with equine chorionic gonadotropin resulted in increased density and number of large luteal cells which increased the capacity of the CL to produce progesterone [37]. Although we were unable to document the effect of letrozole treatment on gonadotropin secretion in the present study, previous studies have shown an increase in gonadotropin secretion after single or 3-day letrozole regimen [15,38,39].…”

Consequences of eight consecutive applications of equine chorionic gonadotropin on ovarian follicle development and ovulation in bos indicus cows

“…Some authors have shown that it can increase preovulatory follicle size and that would end up in a larger Cl (tORtERElla et al, 2013). the size of the Cl is important for progesterone secretion and pregnancy maintenance (RIGOGlIO et al, 2013;MaRtINEZ et al, 2014). however, in previous studies eCG did not influence pre-ovulatory follicle size however it rather enhanced Cl size (BaRUSEllI et al, 2004;pUllEY et al, 2013;MaRQUEZINI et al, 2014).…”

“…an increase in progesterone concentration has also been described as a positive effect of the eCG (SaNtOS et al, 2001;BaRUSEllI et al, 2004;MaRQUEZINI et al, 2014). the eCG acts increasing the number of lutheal cells and mitochondrias that in turn increases pregnenolone synthesis (RIGOGlIO et al, 2013).…”

Effects of Equine Chorionic Gonadotropin on Follicular, Luteal and Conceptus Development of Non-LactatingBos IndicusBeef Cows Subjected to a Progesterone Plus Estradiol-Based Timed Artificial Insemination Protocol

“…The greater weight of CL can be due to the increase in the LF at TAI (Sá Filho et al, 2010b), an increase in the number of large luteal cell or an increase in the proportion between large and small luteal cells (Rigoglio et al, 2012). However, although eCG-treated cows presented larger and heavier CLs, these cows did not present a higher concentration of P4 in the dioestrus.…”