Serotonin inhibition of steroid-induced meiotic maturation in the teleost Fundulus heteroclitus: Role of cyclic AMP and protein kinases

• Published in: Molecular reproduction and development 1998-03, Vol.49 (3), p.333-341
• Main Authors: Cerdà, Joan, Reich, Gerhard, Wallace, Robin A., Selman, Kelly
• Format: Article
• Language: English
• Subjects: 5-HT; Animals; Biological and medical sciences; Cyclic AMP - metabolism; Cyclic GMP-Dependent Protein Kinases - metabolism; Female; Freshwater; Fundamental and applied biological sciences. Psychology; Fundulus heteroclitus; Hydroxyprogesterones - pharmacology; Killifishes; Marine; maturation-inducing steroid; Meiosis - drug effects; Non mammalian vertebrate reproduction; oocyte maturation; Oocytes - cytology; Oocytes - drug effects; Oocytes - metabolism; Oocytes - physiology; protein kinase A; protein kinase C; Protein Kinase C - metabolism; Protein Kinases - metabolism; Serotonin - pharmacology; Vertebrates: reproduction
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/(SICI)1098-2795(199803)49:3<333::AID-MRD14>3.0.CO;2-X

The transduction of the serotonin (5‐HT) signal in Fundulus heteroclitusovarian follicles leading to the inhibition of oocyte meiosis reinitiation (oocyte maturation) in vitro induced by the naturally occurring maturation‐inducing steroid 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP) was investigated. Steroid‐induced oocyte maturation was inhibited by 5‐HT in a dose‐dependent manner; maximum inhibition (90%) was observed with 10−4 M 5‐HT. Groups of follicle‐enclosed oocytes were cultured in the presence of the phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX) and treated with increasing doses of 5‐HT. Serotonin was found to slightly increase the levels of follicular 3′,5′‐cyclic adenosine monophosphate (cAMP) in a dose‐dependent manner; 10−4 M 5‐HT induced approximately a 3‐fold increase in cAMP with respect to the controls. The changes in cAMP were then evaluated in follicles treated with 17,20βP in IBMX‐free culture media in the presence or absence of 10−4 M 5‐HT. The exposure of follicles to 17,20βP alone produced a small and transient reduction in cAMP (40%) within 1–3 hr of steroid stimulation, and these early changes in cAMP appeared associated with a high incidence of germinal vesicle breakdown (80% GVBD) by 24 hr of incubation. Under these conditions, treatment of follicles with 5‐HT also increased significantly the production of cAMP, and when 5‐HT was combined with 17,20βP, the steroid‐mediated reduction in cAMP was prevented and the levels of GVBD inhibited by 95%. Meiosis also was reinitiated with either the protein kinase A (PKA) inhibitor H8 or the protein kinase C (PKC) activator PMA, and the 5‐HT inhibitory action on GVBD was found to be 100‐fold reduced or completely ineffective, respectively. Preincubation of follicles with the PKC inhibitor GF109203x abolished PMA‐induced GVBD in a dose‐dependent manner, whereas this inhibitor had no effect on 17,20βP‐triggered meiotic maturation, indicating that activation of PKC is apparently sufficient but not necessary to reinitiate meiosis. Taken together, these findings suggest that 5‐HT may inhibit 17,20βP‐induced meiotic reinitiation through the activation of a cAMP‐PKA transduction pathway and that PKC possibly induces oocyte maturation by a different pathway than the steroid and thus is not affected by 5‐HT. Mol. Reprod. Dev. 49:333–341, 1998. © 1998 Wiley‐Liss, Inc.