Effects of the isoflavones genistein and equol on the gonadal development of Japanese medaka Oryzias latipes.

Abstract

The estrogenic isoflavone compound genistein recently has been found in the effluents of sewage treatment plants and pulp mills, and the related compound equol has been detected in the runoff from agricultural fields treated with hog manure. Waterborne exposures of Japanese medaka (Oryzias latipes) to equol from soon after hatch to approximately 100 days posthatch induced gonadal intersex (i.e., testis-ova) in males at incidences of 10 and 87% in equol treatments of 0.4 and 0.8 µg/L, respectively. Exposure to the highest test concentration of genistein, 1,000 µg/L, also caused a low incidence (i.e., 12%) of gonadal intersex in male medaka. The ovaries of female medaka from both equol and genistein treatments showed delayed oocyte maturation, atretic oocytes, an enlarged ovarian lumen, proliferation of somatic stromal tissue, and primordial germ cells; responses were concentration dependent. Alterations to externally visible secondary sex characteristics occurred in medaka exposed to both equol and genistein. In treatments with 1,000 µg/L genistein, 72% of male medaka (as identified by the gonadal phenotype) showed feminized secondary sex characteristics. Gonadal intersex and alterations to secondary sex characteristics have been noted in several fish populations around the world. This laboratory study indicates that isoflavone compounds should be considered candidate estrogenic compounds that may be involved in the alteration of sexual development in feral fish populations.

Occurrence of Natural Contaminants of Emerging Concern in the Douro River Estuary, Portugal

“…Concentration of all quantified phytoestrogens were lower than hazardous levels described in the in vivo experiments of Kiparissis et al (2003). In this study, only concentrations of GEN above 1000 lg L -1 produced gonadal intersex in the Japanese medaka (Oryzias latipes).…”

Determination of seventeen endocrine disruptor compounds and their spatial and seasonal distribution in Ria Formosa Lagoon (Portugal)

“…, it is possible that estrogenic endocrine disruption may be induced locally by this phytoestrogen, as reported by others (Kiparissis et al 2003). Endocrine disruption can also be induced by the phytosterol SITO, which is structurally similar to cholesterol.…”

Influence of ovarian stage on transcript profiles in fathead minnow (Pimephales promelas) ovary tissue

“…For example, in female fathead minnows exposed to the aromatase inhibitor fadrozole for 21 d there was a significant reduction in histologically determined ovarian stage, and reduced vitellogenin uptake into developing oocytes (Ankley et al, 2002). Jensen et al (2004) reported increased numbers of early stage follicles and atretic follicles in female fathead minnows exposed to the anti-androgen flutamide for 21 d. Weisbrod et al (2007) reported increased numbers of previtellogenic oocytes and decreased proportions of early and late vitellogenic oocytes in female fathead minnows exposed to >1.2 mg benzophenone-2/L or to 50 ng 17␣-ethynylestradiol for 15 d. Similar types of effects have been observed in zebrafish and medaka (Kiparissis et al, 2003;van der Ven et al, 2003). Such shifts in the relative proportions of differently staged follicles may reflect effects of the chemicals on the fish reproductive axis, and at the same time obscure aspects of the transcript profile that could yield mechanistic insights.…”