Long-term exposure investigating the estrogenic potency of estriol in Japanese medaka (Oryzias latipes)

Abstract

The growth, development, and ERα and Vtg-I gene expressions of Japanese ricefish (Oryzias latipes; medaka) exposed to different concentrations of estriol (E3), including one environmentally relevant concentration, during embryo-adult life stages were evaluated. At the early life stage, fertilized eggs were exposed to 5, 50, 500, 5000 ng/L E3 for 15 days, and the hatched fry were exposed continuously to the same concentrations for an additional 15 days. Exposure to 500 and 5000 ng/L E3 resulted in adverse effects on hatchability and time to hatching. At 5000 ng/L, the gross abnormality rate was increased and the number of females that hatched was twice that of males. When the fish were exposed to 5-5000 ng/L E3 for further 60 days, the male hepatosomatic index (HSI) was increased at 5000 ng/L. The female gonadosomatic index (GSI) was decreased at 500 and 5000 ng/L E3, while the male GSI at 5000 ng/L E3 was increased and sex reversal was also found at this concentration. Quantitative RT-PCR showed that the hepatic vitellogenin-I (Vtg-I) genes were up-regulated in females at 500 and 5000 ng/L E3 and in males at all E3 concentrations, whereas E3 did not affect estrogen receptor α (ERα) mRNA transcription. These results showed that E3 at environmental concentration of 5 ng/L has no adverse effects on growth and development of the Japanese medaka. However, in this study, if we only focused on Vtg gene change in males, E3 had strong estrogenic effects on male medaka under the conditions of these experiments.

Transient exposure to environmental estrogen affects embryonic development of brown trout (Salmo trutta fario)

“…Similarly to the present results, a continuous exposure of freshly fertilized eggs of medaka (Oryzias latipes) to 200 g/L bisphenol A (BPA; ca 18 ng/L EEQ) led to early hatch (Ramakrishnan and Wayne, 2008). Contrary, a continuous estriol (E3) exposure to 500 and 5000 ng/L (ca 0.2 and 1.7 g/L EEQ) delayed time to hatch and reduced hatchability of medaka (Lei et al, 2014). In salmonids, offspring of phytosterol-exposed maturing lake trout (Salmo trutta lacustris) hatched earlier through parental transfer (Lehtinen et al, 1999).…”

Windows of Susceptibility and Consequences of Early Life Exposures to 17β–estradiol on Medaka (Oryzias latipes) Reproductive Success

“…There are growing accounts of the deleterious effects of estrogen contaminant exposure on fish populations. ,− Previous studies of estrogen (e.g., E2β, 17α-ethynylestradiol (EE2), estriol) and wastewater treatment plant effluent exposure during specific temporal or developmental stages ,,,, or through complete life cycles ,, have established that exposure can lead to impaired reproductive success. However, from regulatory or management perspectives, it is difficult to prioritize decisions or mitigation efforts without a clear understanding of the most critical stages of susceptibility.…”

“…Similarly, Hirai et al document differential disruption of fecundity and fertility in Japanese medaka ( Oryzias latipes ) following E2β exposure at two periods, fertilization to 31 days post fertilization and fertilization to 81 days post fertilization . While numerous studies have documented impaired fertility and fecundity in fish following chronic exposures to estrogens and estrogen mimics within both the organizational and activational phases, ,,,, there remains a paucity of information regarding differential reproductive effects of exposure within defined developmental stages. This study examined reproductive dysfunction following exposure during four critical stages of development (susceptibility) in medaka: gonad development, gonad differentiation, development of SSC, and gonad maturation.…”

Multi-parameter risk assessment of forty-one selected substances with endocrine disruptive properties in surface waters worldwide

“…This is important for determining the lowest effective dose on organisms as the doses in acute toxicity studies are much higher. On the example of estriol, the selected (chronic toxicity) study observed effects for 90 days with an effective dose of 46.5 ng/L (Lei et al, 2014), while another (acute toxicity) study performed with the same substance that only lasted one day, used a dose higher than 100 mg/L (Li, 2013).…”