Decreased apoptosis in the forebrain of adult male medaka ( Oryzias latipes) after aqueous exposure to ethinylestradiol

Endocrine disrupting compounds (EDCs), especially those that are estrogenic, are an issue of growing concern because they may ultimately adversely affect wildlife survival. 17-β-Estradiol and its synthetic counterpart, 17-α-ethinylestradiol, two common EDCs, are associated with intersex conditions and impaired male reproductive behavior in fish. Male and female Japanese medaka ( Oryzias latipes) were exposed to 10 ng/l ethinylestradiol for 6 months. Using terminal dideoxynucleotidyl-mediated dUTP nick end-labeling (TUNEL) to quantitate cell death, we found that ethinylestradiol-exposed males had significantly fewer apoptotic cells in the forebrain compared to untreated males and exposed females. Our results show that the effects of ethinylestradiol exposure are highly variable among individuals of the same species and even within tissues of the same individual. Thus, when examining the effects of EDCs on natural populations, data from a variety of tissues should be examined and the interpretation of any effects should include consideration of tissue-specific processes.