Participation of vasoactive intestinal polypeptide in ovarian steroids production during the rat estrous cycle and in the development of estradiol valerate-induced polycystic ovary

Abstract

Vasoactive intestinal polypeptide (VIP) stimulates estradiol and progesterone release from ovarian granulosa cells in vitro. Very little information is available as to the role VIP plays in the control of steroid secretion during reproductive cyclicity and in ovarian pathologies involving altered steroid secretion. In this study, we determined the involvement of VIP in regulating ovarian androgen and estradiol release during estrous cyclicity and estradiol valerate (EV)-induced polycystic ovarian development in rats. Our findings show that androgen and estradiol release from ovaries obtained during different stages of rat estrous cycle mimic cyclic changes in steroid release observed in vivo with maximal release occurring during late proestrus. VIP increased androgen release from ovaries of all cycle stages except late proestrus and estradiol release from all cycle stages. Increases in VIP-induced androgen and estradiol release were maximal at early proestrus. Inclusion of saturating concentrations of androstenedione increased magnitude of VIP-induced estradiol release at diestrus and estrus but not proestrus. Magnitude of VIP-induced androgen and estradiol release tended to be greater in the ovaries from EV-treated rats with polycystic ovary compared with estrous controls. At the tissue level, ovarian VIP concentration was cycle stage dependent with highest level seen in diestrus. Maximum concentration of VIP was found in EV-treated rats. Changes in VIP were inversely related to changes in ovarian nerve growth factor, a neuropeptide involved in ovarian androgen secretion. These results strongly suggest that intraovarian VIP participates in the control of estradiol secretion during the rat estrous cycle and possibly in the maintenance of increased ovarian estradiol secretory activity of EV-treated rats.

Effect of Korean red ginseng extract in a steroid-induced polycystic ovary murine model

“…Cycling female rats by a single intramuscular injection with estradiol valerate (EV) demonstrate a feature common to most forms of PCO (Brawer et al, 1986), with the lack of dominant preovulatory follicles and multiple medium-sized antral follicles containing an enlarged, androgen-producing thecal layer (Lara et al, 2000). EV-administered rats share several attributes with human PCOS such as endocrinologic and morphological characteristics (Parra et al, 2007). Activity in the ovarian sympathetic nerves of PCOinduced rats is higher than in the nerves of normal cycling rats, as evident by a higher release and content of norepinephrine (NE) in the ovaries with a lower expression of adrenoceptors in the ovarian compartment (Barria et al, 1993;Lara et al, 1993;Lara et al, 2000).…”

Vasoactive Intestinal Peptide Improves the Survival and Development of Caprine Preantral Follicles after in vitro Tissue Culture

“…VIP has been shown to stimulate in vitro androgen and estradiol release [Davoren and Hsueh, 1985;Parra et al, 2007]. In addition, VIP stimulation induced aromatase and follicle-stimulating hormone (FSH) receptor expression at both the transcript and protein level in the rat neonatal ovary several days before the ovary became responsive to gonadotropins [Mayerhofer et al, 1997].…”

Changes in the Cholinergic Innervation Pattern of Porcine Ovaries with Cysts Induced by Dexamethasone Administration

“…Furthermore, we have observed an increase in the density of SOM-IR fibre population within the medullar part of the ground plexus, while simultaneously the number of VAChT-IR nerve fibres decreased in the latter structure. The increased population of VIP-IR nerve fibres within the medullar part of cystic ovaries was earlier observed following injection of DXM from the follicular phase of the estrous cycle (Kozłowska et al 2008), and it has also been shown that the concentration of VIP rose markedly in the estradiol valerate (EV)-induced polycystic ovaries (Parra et al 2007). However, in the DXM-treated gilts from the follicular phase, in contrast to the current report, the density of VIP-IR nerve fibres near cysts and within the cortical part of the ground plexus as well as VAChT-IR in the area of the medullar part of the ground plexus was similar to those revealed in the CON group (Kozłowska et al 2008).…”