Transcriptional and Physiological Responses Induced by Binary Mixtures of Drospirenone and Progesterone in Zebrafish (Danio rerio)

Drospirenone (DRS) is a synthetic progestin increasingly used in oral contraceptives with similar effects to progesterone (P4). Wild fish are exposed to DRS and P4 through wastewater. However, the effects of DRS on fish, both as an individual compound and in mixtures, have not been extensively studied. Therefore, in this study, global gene expression profiles of ovary and brain of female zebrafish (Danio rerio) were characterized after exposure to 55, 553, and 5442 ng/L DRS for 14 days. The effects were then compared to the observed responses after exposure to mixtures of DRS and P4 (DRS+P4: 27 + 0.8, 277 + 8 and 3118 + 123 ng/L). Transcriptomics findings were related to the changes in vitellogenin protein concentrations in the blood, morphology, and histology of gonads. Multivariate analysis indicated tissue-, dose-, and treatment-dependent expression profiles. Genes involved in steroid hormone receptor activity and circadian rhythm were enriched in DRS and mixture groups, among other pathways. In mixtures, the magnitude of response was dose- and transcript-dependent, both at the molecular and physiological levels. Effects of DRS and P4 were additive for most of the investigated parameters and occurred at environmentally relevant concentrations. They may translate to adverse reproductive effects in fish.