AI Article Synopsis
- Norethindrone (NET), a synthetic progestin, poses risks to aquatic life, prompting a study on its effects on marine medaka larvae over 190 days at two concentrations: 7.6 ng/L and 80.1 ng/L.
- Exposure to 80.1 ng/L NET resulted in an all-male population and reduced male growth, while 7.6 ng/L NET increased the male-to-female ratio, hindered male growth, and delayed female ovary maturation but accelerated sperm maturation in males.
- The study found significant changes in gene expression related to the hypothalamic-pituitary-gonadal (HPG) axis, with NET exposure
Article Abstract
Norethindrone (NET) is a widely used synthetic progestin, which appears in water environments and threatens aquatic organisms. In this study, marine medaka (Oryzias melastigma) larvae were exposed to 7.6 and 80.1 ng/L NET for 190 days. The effects of NET on growth, sex differentiation, gonad histology and transcriptional expression profiles of hypothalamic-pituitary-gonadal (HPG) axis-related genes were determined. The results showed that exposure to 80.1 ng/L NET caused an all-male marine medaka population and significantly decreased the growth of males. Exposure to 7.6 ng/L NET increased the ratio of males/females in the marine medaka population, decreased the growth of males and delayed the ovary maturation in females. However, the sperm maturation was accelerated by 7.6 or 80.1 ng/L NET. In females, the transcription levels of cytochrome P450 aromatase (cyp19a1a) and progesterone receptor (pgr) in ovaries, glucocorticoid receptor (gr) and vitellogenin (vtg) in livers were suppressed after exposure to 7.6 ng/L NET, which may cause delayed ovary maturation. In males, NET significantly decreased the transcription levels of follicle stimulating hormone β (fshβ) and Luteinizing hormone β (lhβ)in the brain, Estrogen receptor β (erβ)，gr and pgr in the liver, and vitellogenin receptor (vtgr) in the testes, while NET of 80.1 ng/L led to a significant up-regulation of steroidogenic acute regulatory protein (star) in the testes of males. These results showed that NET could influence growth, sex differentiation and gonadal maturation and significantly alter the transcriptional expression levels of HPG axis-related genes.
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| http://dx.doi.org/10.1002/tox.23477 | DOI Listing |
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