Mixture effects of levonorgestrel and ethinylestradiol : Estrogenic biomarkers and hormone receptor mRNA expression during sexual programming

• Synthetic progesterone (progestins) and estrogens are widely used pharmaceuticals. Given that their simultaneous unintentional exposure occurs in wildlife and also in human infants, data on mixture effects of combined exposures to these hormones during development is needed. Using the Xenopus (Silurana) tropicalis test system we investigated mixture effects of levonorgestrel (LNG) and ethinylestradiol (EE2) on hormone sensitive endpoints. After larval exposure to LNG (0.1 nM), or EE2 (0.1 nM) singly, or in combination with LNG (0.01, 0.1, 1.0 nM), the gonadal sex ratio was determined histologically and hepatic mRNA levels of genes encoding vitellogenin (vtg beta1) and the estrogen (esr1, esr2), progesterone (ipgr) and androgen (or) receptors were quantified using quantitative PCR. All EE2-exposed groups showed female-biased sex ratios and increased vtgbeta1 mRNA levels compared with the controls. Compared with the EE2-alone group (positive control) there were no significant alterations in vtg betal levels or in sex ratios in the co-exposure groups. Exposure to LNG-alone caused an increase in ar mRNA levels in females, but not in males, compared to the controls and the co-exposed groups, indicating that co-exposure to EE2 counteracted the LNG-induced or levels. No treatment related impacts on the mRNA expression of esr1, esr2, and ipgr in female tadpoles were found, suggesting that these endpoints are insensitive to long-term exposure to estrogen or progestin. Due to the EE2-induced female-biased sex ratios, the mRNA expression data for the low number of males in the EE2-exposed groups were not statistically analyzed. In conclusion, our results suggest that induced vtg expression is a robust biomarker for estrogenic activity in exposure scenarios involving both estrogens and progestins. Developmental exposure to LNG caused an induction of hepatic or mRNA expression that was antagonized by combined exposure to EE2 and LNG. To our knowledge this is the first study to report effects of combined exposures to EE2 and LNG during the period of sexual programming. (C) 2015 Elsevier B.V. All rights reserved.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Farmakologi och toxikologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Pharmacology and Toxicology (hsv//eng)

Nyckelord

Endocrine disruption

Androgen receptor

Sex differentiation

Pharmaceuticals

Amphibians

Vitellogenin

Publikations- och innehållstyp

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