GONZÁLEZ A, FERNANDINO JI, CHALDE T, ELISIO M, MIRANDA LA, SOMOZA GM. Sex hormone-binding globulin expression during oogenesis. Its regulation by xenosteroids in pejerrey fish.

GONZALEZ A; FERNANDINO JI; CHALDE T; ELISIO M; MIRANDA LA; SOMOZA GM

Buenos Aires

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

SETAC

Sex hormone-binding globulins (SHBGs) are carrier serumproteins involved in the transport of sex steroids in blood. SHBGs are related toreproduction because they regulate the plasma metabolic clearance rate of sexsteroids by controlling its bioavailability. It is known that the mainexpression site of SHBG in teleost fish is the liver, but there is littleknowledge about its regulation. In female fish, one of the most important reproductiveprocesses, that take place in the liver, is vitellogenesis, and this process ismainly regulated by the sex steroid 17β-estradiol (E2) synthetizedin the ovary. However, the involvement of sex steroids in the regulation ofSHBG expression is still under debate in teleosts. Additionally, it is wellknown that xenoestrogens can mimic the actions of endogenous estrogens. In thiscontext, the main objective of this study was to analyze if natural and/or syntheticsex steroids can regulate shbg geneexpression. First, shbg-mRNA abundancewas assessed in liver during oogenesis in wild fish throughout one sex cycle. Thenwe assessed the in vitro exposure of vitellogenicfemale liver slices to the following estrogens: E2 and17α-ethinylestradiol (EE2), and the androgens: testosterone (T) and5α-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 highestlevels at pre-vitellogenesis and lowest at advanced vitellogenesis stages. Theexpression of shbg showed negativecorrelations with plasmatic sex steroids levels (R=0.8 for E2 andR=0.58 for T), indicating that these steroid could be involved in a negativefeedback mechanism. On the other hand, invitro culture of vitellogenic female liver slices, showed that E2,EE2 and DHT but not T, increased shbg-mRNAabundance, being E2 the most potent steroid (increasing 10 times withrespect to basal levels at all concentrations tested). Taken together, theseresults suggest that shbg geneexpression can be regulated by sex steroid and xenosteroids. Thus, the presenceof these compounds in the environment could modulate the steroidsbioavailability through the regulation of SHBG expression.