Anchoring ethinylestradiol induced gene expression changes with testicular morphology and reproductive function in the medaka

This study assessed the implications of a 14 day sub-chronic exposure of ethinylestradiol (EE2; 1.0 or 10.0 µg/L EE2) on male medaka fertility, testicular histology and testicular gene expression. The findings demonstrate that a 14 day exposure to EE2 induced impaired male reproductive capacity and time- and dose-dependent alterations in testicular morphology and gene expression. The average fertilization rate/day following the exposure for control, 1.0 and 10.0 µg/L EE2 was 91.3% (±4.4), 62.8% (±8.3) and 28.8% (±5.8), respectively. The testicular morphologic alterations observed include increased germ cell apoptosis, decreased germinal epithelium and thickening of the interstitium. The morphologic changes observed were highly associated with gene expression changes observed using a medaka-specific microarray. A pathway analysis of the differentially expressed genes emphasized genes and pathways associated with apoptosis, cell cycle and proliferation, collagen production/extracellular matrix organization, hormone signaling, male reproduction and protein ubiquitination among others. Six month old male medaka were exposed to ethinyl estradiol (EE2) for a 14 day time period. Treatment exposures were completed in triplicate including DMSO (vehicle control), 1.0 µg/L EE2, and 10.0 µg/L EE2. Fish were sampled for gene expression on days 1, 7 and 14 of exposure. Five male fish were placed in 2-liter beaker replicates for each treatment and sampling time point.