steroids 71 ( 2 0 0 6 ) 435–444 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/steroids Sexual dimorphism in esterified steroid levels in the gastropod Marisa cornuarietis: The effect of xenoandrogenic compounds Gemma Janer a , Angeliki Lyssimachou a , Jean Bachmann b ,J¨ org Oehlmann b , Ulrike Schulte-Oehlmann b , Cinta Porte a,∗ a Environmental Chemistry Department, IIQAB-CSIC, Jordi Girona 18, 08034 Barcelona, Spain b Johann Wolfgang Goethe-University Frankfurt am Main, Department of Ecology and Evolution-Ecotoxicology, Siesmayerstr. 70, D-60054 Frankfurt, Germany article info Article history: Received 16 June 2005 Received in revised form 4 January 2006 Accepted 11 January 2006 Published on line 17 April 2006 Keywords: Esterification Testosterone Estradiol Gastropod Imposex Acyl-CoA acyltransferase abstract Molluscs can conjugate a variety of steroids to form fatty acid esters. In this work, the freshwater ramshorn snail Marisa cornuarietis was used to investigate sex differences in endogenous levels of esterified steroids. Testosterone and estradiol were mainly found in the esterified form in the digestive gland/gonad complex of M. cornuarietis, and males had higher levels of esterified steroids than females (4–10-fold). Additionally, the ability of sev- eral xenobiotics, namely tributyltin (TBT), methyltestosterone (MT) and fenarimol (FEN) to interfere with the esterification of testosterone and estradiol was investigated. All three compounds induced imposex – appearance of male sexual characteristics in females. Expo- sure to TBT led to a decrease in both esterified testosterone (60–85%) and estradiol (16–53%) in females after 100 days exposure, but had no effect on males. Exposure to FEN and MT did not alter levels of esterified steroids in males or in females, although exposed females devel- oped imposex after 150 days exposure. The decrease in esterified steroids by TBT could not be directly linked with a decrease in microsomal acyl-CoA:testosterone acyltransferase (ATAT) activity, which catalyzes the esterification of steroids. In fact, ATAT activity was marginally induced in organisms exposed to TBT for 50 days (1.3-fold), and significantly induced in males and females exposed to MT for 50 days (1.8- and 1.5-fold, respectively), whereas no effect on ATAT activity was observed after 150 days exposure. © 2006 Elsevier Inc. All rights reserved. 1. Introduction Sex steroids, such as progesterone, testosterone and estra- diol, are present in molluscs [1], and several studies have demonstrated the ability of these organisms to synthesize sex steroids from precursors, such as cholesterol or pregnenolone [2–5]. Proteins with a high binding affinity for sex steroids have been found in Octopus vulgaris [6], and an estrogen receptor ∗ Corresponding author. Tel.: +34 93 4006175; fax: +34 93 2045904. E-mail address: cpvqam@cid.csic.es (C. Porte). ortholog gene has been sequenced in the mollusc Aplysia cal- ifornica [7], suggesting that steroids might also function via interaction with steroid receptors in molluscs. In addition, rapid non-genomic effects of estradiol have been demon- strated in mussel neural tissue (increase in nitric oxide release [8]) and in mussel hemocytes (increase in calcium concen- trations and changes in the phosphorylation of signal trans- ducers and transcription activators [9]). Although there are 0039-128X/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.steroids.2006.01.012