Vasoactive intestinal peptide stimulates oocyte maturation, steroidogenesis, and cyclic adenosine 3',5'-monophosphate production in isolated preovulatory rat follicles.
Vasoactive intestinal peptide (VIP) is present in the rat ovary and has been shown to stimulate cyclic adenosine 3',5'-monophosphate (cAMP) and progesterone production in cultured rat granulosa cells. In the present study, VIP-stimulated cAMP production has been studied in relation to steroid accumulation and oocyte maturation in isolated preovulatory rat follicles. VIP stimulated resumption of meiosis (oocyte maturation) in up to 60% of the follicle-enclosed oocytes after 6 h at 1 microM (control, 1.8%; luteinizing hormone 99%). The effect was time- and dose-dependent up to 6 h and was seen with both natural and synthetic VIP. VIP also stimulated the accumulation of steroids (estrogen, 2.3-fold; testosterone, 2.0-fold; and progesterone, 1.6-fold increase after 6 h of incubation) and lactate (2.6-fold) by the follicles. VIP-increased tissue levels of cAMP in the follicle were dose- and time-dependent. This effect was potentiated by a phosphodiesterase inhibitor. When isolated oocyte-cumulus complexes were studied, VIP caused a transient inhibition of spontaneous oocyte maturation, and demonstrated no effect on denuded oocytes. These results extend earlier preliminary observations on the ability of VIP to induce meiotic maturation of follicle-enclosed oocytes. Our results also show that VIP can stimulate steroid and lactate accumulation in the isolated follicles. The pattern of steroids produced suggests an effect both on the theca- and granulosa cells. We also show that VIP can delay spontaneous oocyte maturation. These effects appeared, at least partially, to be mediated by cAMP.
Törnell
J
J
Department of Physiology, University of Göteborg, Sweden.
Carlsson
B
B
Hillensjö
T
T
D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D005260:Female; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D007773:Lactates / Q000378:metabolism; D009865:Oocytes / Q000254:growth & development / Q000502:physiology*; D006080:Ovarian Follicle / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D014660:Vasoactive Intestinal Peptide / Q000502:physiology*
D012739:Gonadal Steroid Hormones; D007773:Lactates; D014660:Vasoactive Intestinal Peptide; D000242:Cyclic AMP