Meeting Abstract
P2.129 Tuesday, Jan. 5 Inhibition of 11β-HSD reduces 11-Ketotestosterone levels in Lythrypnus dalli PRADHAN, Devaleena S.*; GROBER, Matthew S.; Georgia State University; Georgia State University dpradhan1@student.gsu.edu
In many fish species, 11-Ketotestosterone (KT) is the primary androgen responsible for activating male breeding morphology and behavior. KT synthesis occurs via the sequential action of 11&beta-hydroxylase (converts T to 11-hydroxyT) and 11&beta-hydroxysteroid dehydrogenase (11&beta-HSD, converts 11-hydroxyT to KT). Carbenoxolone (CBX), a specific 11&beta-HSD inhibitor has been widely used to study glucocorticoid synthesis in the stress axis. Here, we asked whether systemic administration of CBX affects KT levels and sex typical morphology in Lythrypnus dalli, a bi-directionally sex changing fish in which 1) both sexes have similar levels of systemic, brain, and gonadal KT, 2) brain KT levels are several fold higher than the gonads, and 3) both systemic and brain KT increase transiently during protogynous sex change. Adult L. dalli were collected off the coast of California. After assessing body condition, opposite sex pairs were implanted IP with either 3:1 beeswax:CBX or beeswax only. Water-borne steroids were collected in isolated fish 1hr, 1d, and 4d after treatment. KT levels were similar in all groups 1 hr after treatment, and there was no effect of CBX in females. After 1d, there was a 48% decrease in KT in CBX implanted males. These levels were 30% lower than controls, but returned to baseline at 4d. There were no significant changes in body length, genitalia or gross gonad morphology 7d after CBX treatment. These results indicate sex differences in the effect of IP CBX implants. As CBX does not cross the blood brain barrier, the decrease we observed in males is likely due to gonad specific inhibition, suggesting low rates of ovarian KT synthesis and high rates of brain KT synthesis. The recovery at 4d suggests that KT inhibition in testis may be compensated by KT synthesis from the brain.
