Relationship between Sex Steroid and Vitellogenin Concentrations in Flounder ( Platichthys flesus ) Sampled from an Estuary Contaminated with Estrogenic Endocrine-Disrupting Compounds

Abstract

High concentrations of vitellogenin (VTG; egg yolk protein) have previously been found in male flounder (Platichthys flesus) from several UK estuaries; these levels have been ascribed to the presence of estrogenic endocrine-disrupting compounds (EDCs). Gonadal abnormalities, including intersex, have also been recorded in these estuaries. However, there is no firm evidence to date that these two findings are causally linked or that the presence of estrogenic EDCs has any adverse population effects. In the present study, we examined the relationship between concentrations of VTG and sex steroids (11-oxotestosterone in males and 17β-estradiol in females) in specimens of flounder captured from the estuary of the River Mersey. We first questioned whether the high concentrations of VTG in male and immature female flounder were indeed caused by a direct effect of exogenous EDCs and not indirectly via the endogenous secretion of 17β-estradiol. The data favored the direct involvement of estrogenic EDCs. We then questioned whether the presence of estrogenic EDCs not only stimulated inappropriate VTG synthesis but whether it might also have had a negative effect on endogenous steroid secretion. It should be noted that the predicted consequences of a drop in steroid secretion include smaller gonads, smaller oocytes, fewer numbers of sperm, and depressed spawning behavior. This question was more difficult to answer because of the strong effect of the seasonal reproductive cycle and stage of maturation on steroid concentrations. However, matched by month of capture and stage of maturation, both 17β-estradiol in females and 11-keto-testosterone in males were in most cases significantly lower in those years when VTG concentrations were higher.

Enzyme-linked immunosorbent assay (ELISA) measurement of vitellogenin in plasma and liver histopathology in barfin plaice Liopsetta pinnifasciata from Amursky Bay, Sea of Japan

“…Comparable or higher levels of Vg were found in males inhabiting the polluted areas. The Vg concentration in P. flesus males from the Mersey estuary was 0.32 ± 0.3 lg/ml in September and 20.262 ± 9.133 mg/ml in December (Scott et al 2006). In P. putnami males from the Saint Lawrence Estuary, the average Vg concentration in plasma was 0.16 ± 0.13 lg/ml (Roy et al 2004).…”

“…These data confirm the results of an earlier study in which the plasma Vg concentration of Platichthys flesus collected from Mersey estuary was 0.9 ± 0.4 mg/ml at the initial stage of oogenesis and 5.797 ± 1.009 mg/ml at the active vitellogenesis stage, in which vitellogenic oocytes were present in the ovary. Concentrations up to 18.319 ± 3.139 mg/ml were found in vitellogenic females in different years (Scott et al 2006). In P. putnami females captured in the Saint Lawrence Estuary, on the west Atlantic coast, plasma Vg was low (16.41 ± 11.95 lg/ml) if fish were captured after spawning and were only starting vitellogenesis (May) (Roy et al 2004).…”

“…Male fish can also synthesise measurable amounts of this protein in response to oestrogenic stimulation. Due to this ability, Vg has been proposed as a biomarker of exposure to oestrogenic chemicals in the environment Heppell et al 1995;Tyler et al 1996;Solé et al 2001;Scott et al 2006;Leonardi et al 2009). These substances can imitate the effects of natural oestrogenic hormones, such as 17b-estradiol, and adversely affect normal physiological and endocrine regulation in living organisms (Golden et al 1998).…”

Evidence for estrogenic endocrine disruption in an offshore flatfish, the dab (Limanda limanda L.)

“…This was omitted from the statistical comparison between VTG and E 2 concentrations. As in male cod (Scott et al, 2006b) and male flounders (Scott, Katsiadaki, Kirby, & Thain, 2006a), there was no evidence that elevated VTG concentrations in male dabs were related to their stage of reproductive maturity or to plasma E 2 concentrations.…”

Survey of contamination of estrogenic chemicals in Japanese and Korean coastal waters using the wild grey mullet (Mugil cephalus)

“…Similar changes in VTG levels was observed in the UK. VTG levels of the male flounder of the Mersey Estuary in the UK decreased for six years (Scott et al, 2006b). It is difficult to prove this phenomenon through evidence.…”