Sex Hormone-Binding Globulin Expression During Oogenesis. Its Regulation by Xenosteroids in Pejerrey Fish

GONZÁLEZ, ANELISA; FERNANDINO, JUAN I.; CHALDE, TOMÁS; ELISIO, MARIANO; MIRANDA, LEANDRO A.; SOMOZA, GUSTAVO M.

Buenos Aires

Congreso; 11th SETAC Latin American Biennial Meeting; 2015

Sex hormone-binding globulins (SHBGs) are carrier serum proteins involved in the transport of sex steroids in blood. SHBGs are related to reproduction because they regulate the plasma metabolic clearance rate of sex steroids by controlling its bioavailability. It is known that the main expression site of SHBG in teleost fish is the liver, but there is little knowledge about its regulation. In female fish, one of the most important reproductive processes, that take place in the liver, is vitellogenesis, and this process is mainly regulated by the sex steroid 17β-estradiol (E2) synthetized in the ovary. However, the involvement of sex steroids in the regulation of SHBG expression is still under debate in teleosts. Additionally, it is well known that xenoestrogens can mimic the actions of endogenous estrogens. In this context, the main objective of this study was to analyze if natural and/or synthetic sex steroids can regulate shbg gene expression. First, shbg-mRNA abundance was assessed in liver during oogenesis in wild fish throughout one sex cycle. Then we assessed the in vitro exposure of vitellogenic female liver slices to the following estrogens: E2 and 17α-ethinylestradiol (EE2), and the androgens: testosterone (T) and 5α-dihydrotestosterone (DHT). All steroids were tested at the following concentrations: 0.05, 0.5, 5 and 50 ng/ml. The results showed that shbg-mRNA abundance varied throughout pejerrey oogenesis, with the highest levels at pre-vitellogenesis and lowest at advanced vitellogenesis stages. The expression of shbg showed negative correlations with plasmatic sex steroids levels (R=0.8 for E2 and R=0.58 for T), indicating that these steroid could be involved in a negative feedback mechanism. On the other hand, in vitro culture of vitellogenic female liver slices, showed that E2, EE2 and DHT but not T, increased shbg-mRNA abundance, being E2 the most potent steroid (increasing 10 times with respect to basal levels at all concentrations tested). Taken together, these results suggest that shbg gene expression can be regulated by sex steroid and xenosteroids. Thus, the presence of these compounds in the environment could modulate the steroids bioavailability through the regulation of SHBG expression.