Effects of Vasoactive Intestinal Polypeptide upon Ovarian Steroids, Ovum Transport and Fertility in the Rabbit 1

Abstract

The purpose of this study was to determine the effects of infused vasoactive intestinal polypeptide (VIP) upon reproductive function in the female rabbit. Intravenous infusions of VIP (37.5, 75, and 150 pmol/kg per min) induced acute dose-dependent increases in plasma progesterone (P) but not estradiol (E2) or testosterone (T) in estrous rabbits. This P effect was not associated with an increase in plasma prolactin (Prl) and was not altered by pretreatment with a Prl-inhibiting regimen of bromocriptine. In rabbits stimulated to ovulate with 75 IU human chorionic gonadotropin (hCG) and coitus, plasma P and E2 increased, reaching a peak at 180 min following stimulation. VIP (75 pmol/kg per min) infused from 120 to 180 min following the ovulatory stimuli increased this P peak but did not effect E2 levels. This VIP infusion had no effect upon fertility or upon the number of corpora lutea, uterine implants, or viable conceptuses. Infusions of VIP for 60 min at the P peak, and for 240 min at the time of ovulation, had no significant effect upon ovum pickup or the rate of ovum transport. These observations suggest that 1) VIP infusions in rabbits can increase plasma P from both the basal levels of estrus and from the peak levels preceding ovluation. 2) Infusions of VIP at the time of the preovulatory steroid surge or during ovulation have little effect upon fertility or gamete transport in the rabbit. 3) Endogenous VIP may play a role in the regulation of P secretion in the rabbit.

Immunocytochemical Localization of Vasoactive Intestinal Peptide and Neuropeptide Y in the Bovine Ovary

“…This is supported by the demonstrated constrictive effect of NPY and the relaxant effect of VIP on the rabbit ovarian artery [13]. The localization in the ovarian stroma between preantral follicles may point to an effect on steroidogenic cells in the ovary [30][31][32] or on smooth muscle cells in the follicular wall [33,34], or to a role in the initiation of follicular development [8]. In this latter study, in the monkey ovary, the authors observed VIP fibers in close association with follicles; some primordial follicles were even found to be selectively innervated by VIP-ergic fibers that almost completely encircled each follicle.…”

Identification of Subpopulations of Rat Granulosa Cells: Sedimentation Properties and Hormonal Responsiveness*

“…However, several findings indicate that VIP may be important in mammalian ovarian functions: 1) VIPergic nerve terminals have been shown by immunofluorescence and immunohistochemical methods to be present in ovarian stroma (31)(32)(33); 2) iv infusion of VIP into rabbits produces a rapid rise in plasma progesterone (34); and 3) VIP, independent of FSH, induces steroidogenic responses in rat granulosa cells (7). The latter study demonstrated that these responses were specific for VIP, were dose related, and the rank order potency for VIP and its congeners was in agreement with that found for other tissues.…”

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

“…Previous studies have found that norepinephrine (NE) acts on b 2 -adrenergic receptors present in theca and granulosa cells and stimulates progesterone (P 4 ) and androgens but not estradiol secretion . In contrast to NE, vasoactive intestinal peptide (VIP), another neuropeptide found in ovarian nerves, stimulates estradiol and P 4 release from cultured granulosa cells and whole ovaries in vitro (Davoren & Hsueh 1985), P 4 release in vivo (Fredericks et al 1983), and androgen release from ovarian fragments in vitro ). These effects may be related to the ability of VIP to enhance the synthesis of the cholesterol side-chain cleavage enzyme complex (Trzeciak et al 1986), the rate-limiting step in P 4 biosynthesis and the activity of the aromatase enzyme complex (George & Ojeda 1987).…”