Aquatic Toxicology 99 (2010) 256–262 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Reproductive responses in fathead minnow and Japanese medaka following exposure to a synthetic progestin, Norethindrone Peter Paulos a , Tamsin J. Runnalls b , Gopi Nallani a , Tom La Point a , Alexander P. Scott c , John P. Sumpter b , Duane B. Huggett a,∗ a Department of Biology, University of North Texas, Denton, TX, USA b Institute for the Environment, Brunel University, Uxbridge, Middlesex UB8 3PH, UK c CEFAS – Centre for Environment Fisheries and Aquaculture Science, Barrack Road, Weymouth, Dorset DT4 8UB, UK article info Article history: Received 17 June 2009 Received in revised form 22 April 2010 Accepted 4 May 2010 Keywords: Progestins Fish reproduction Pharmaceuticals abstract Synthetic progestins, such as Norethindrone (NET), are common ingredients in oral contraceptives and in treatment for post-menopausal problems. Given the widespread use of oral contraceptives and post- menopausal treatments, several reports have targeted and identified progestins in aquatic environments. In fish, progestins play an important role in the stimulation of oocyte final maturation and ovulation in females, stimulation of spermiation and sperm motility in males, and the initiation of meiosis in both sexes. They also have a role as pheromones in some species. Given the pivotal role that progestins play in reproduction, their appreciable daily dose (i.e. g to mg range in contraceptives and hormone replacement therapies) and continuous use pattern, it is important to understand the potential risk these compounds pose once discharged into the aquatic environment. Since little published data are available on this class of compounds, our research focused on the reproductive effects of NET on the fathead minnow and Japanese medaka. A 28 day static-renewal reproduction study with Japanese medaka indicated that NET produces a significant decrease in fecundity at aqueous concentrations ≥25 ng/L. A 21 day flow- though fathead minnow reproduction study also demonstrated that NET causes a significant decrease in fecundity in the low ng/L range. Fathead minnow morphological changes (i.e. female fin spots) suggest that NET exposure may have a potent androgenic effect on fish; however, plasma 11-Ketotestosterone (11-KT) concentrations were reduced in males at the highest exposure concentration. Collectively, these data indicate that further investigation of reproductive responses associated with synthetic progestins is warranted. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Pharmaceutical products and metabolites in the environment have been an increasingly researched area, as well as being a topic of regulatory interest. Much of the attention has focused on endocrine disruption associated with the oral contraceptive ingredient 17- ethinyl estradiol. While attention has been given to the potential impacts associated with synthetic estrogens in oral contraceptives (Caldwell et al., 2008), little research has focused on other hor- mones used in contraception. Many oral contraceptives contain synthetic progestins, which to some extent mimic endogenous pro- gesterone. Progestins are also frequently used by post-menopausal women in hormone replacement therapy. Erkkola and Landgren (2005) hypothesized that in combined oral estrogen/progestin con- ∗ Corresponding author at: Institute of Applied Science, Department of Biology, Denton, TX 76203, USA. Tel.: +1 940 891 6956. E-mail address: dbhuggett@unt.edu (D.B. Huggett). traceptives, it is actually progestin that provides the contraceptive effect. Some of the first synthetic progestins were introduced for clinical use over 40 years ago and had undesirable side effects (e.g., androgenic activity). The newer generation of progestins have far fewer side effects as they are more specific for the progesterone receptor (Erkkola and Landgren, 2005). Synthetic progestins have been measured in the environment at low ng/L levels, but few eco- toxicological data are available (Viglino et al., 2008; Vulliet et al., 2007; Pu et al., 2008; Fernandez et al., 2007; Andersson et al., 2006; Kuch and Ballschmitter, 2001). In humans, progesterone and its derivatives are key hormonal components in the regulation of normal female reproductive func- tion. The primary site for progesterone synthesis is the ovary, with intracellular progesterone receptor isoforms (PR-A and PR- B) responsible for mediating its activity (Conneely et al., 2002). Progesterone is involved in the regulation of uterine function during the menstrual cycle, development of the endometrium, and implantation (Spencer and Bazer, 2002). Progesterone is also known to have a significant function in spermatogenesis, being an 0166-445X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2010.05.001