APPLEBAUM, Scott; NUNEZ, Scott; University of Texas at Austin; University of Texas at Austin: Mechanisms of stress-induced changes in ovarian steroidogenesis in the Atlantic croaker.
Stress can rapidly alter plasma sex steroid concentrations in a variety of vertebrates including teleosts. The mechanisms precipitating these changes are unclear; however, a disruption of steroidogenesis is likely involved. Plasma concentrations of epinephrine, ACTH, and glucocorticoids also increase rapidly after stress, and could potentially mediate the observed changes in sex steroid titers. Aromatase converts testosterone to estradiol and is therefore an important regulator of ovarian development and oogenesis. Stress induced changes in aromatase expression and/or activity could precipitate reductions in reproductive success. With this possibility in mind we have initiated a study examining the regulation of aromatase by stress hormones. We have isolated and begun the characterization of a cDNA encoding an ovarian form of Atlantic croaker (Micropogonias undulatus) aromatase. Further, we used in vitro ovarian tissue incubations to identify the effects of several primary mediators of the vertebrate stress response (epinephrine, ACTH, cortisol) on aromatase activity, aromatase mRNA expression and estradiol production. The deduced amino acid sequence of Atlantic croaker aromatase is 28-83% identical to other aromatase proteins. The mRNA encoding this form of aromatase is detected in the ovary, but not in brain, gill, head kidney, heart, liver, or olfactory epithelia. There is a negative correlation between ovarian aromatase expression and gonadosomatic index. ACTH (5 U/ml) increased both basal and hCG-stimulated estradiol synthesis in isolated ovarian follicles. Cortisol (10 uM) decreased estradiol synthesis in ovarian tissue incubations and inhibited the stimulatory effect of hCG. While stress hormones appear to have no effect on basal aromatase expression, preliminary results indicate ACTH and cortisol can alter hCG-regulated aromatase expression.
