Characterization of the Ovarian Corticotropin-Releasing Factor System and its anti-steroidogenic effects in Zebrafish

Abstract

The primary objective of this thesis was to characterize the ovarian corticotropin-releasing factor (CRF) system in the zebrafish (Danio rerio) and determine its effects on local steroidogenesis. All components of the CRF systems in zebrafish are expressed in the ovary. The mRNA levels of CRFb, the CRF receptor subtype CRF-R1, and the CRF binding protein were found to vary with respect to daily cycles of ovulation. CRF was also shown to inhibit human chorionic gonadotropin stimulated production of 17 estradiol and testosterone by mid-vitellogenic and full grown follicles, respectively. These actions were mediated by the CRF-R1 receptor and reduced expression of the steroidogenic enzymes StAR and aromatase. Results also suggest that the anti-steroidogenic effects of CRF may be mediated via downstream actions of local ACTH on the melanocortin 2 receptor. Overall, these results provide original evidence of a functional CRF system in the zebrafish ovary with anti-steroidogenic effects.