RESUMEN
The objective of this study was to determine how the short-term exposure to a supraphysiological concentration of waterborne 17ß-estradiol (E2) influences on melatonin (Mel) and thyroxine (T4) concentrations in plasma and E2 and 11-ketotestosterone (11-KT) concentrations in plasma and gonads in both sexes of round goby (Neogobius melanostomus) during the pre-spawning, spawning, late spawning and non-spawning phases. The experimental protocol was based on short-term, repeated exposures of fish to a supraphysiological dose of waterborne E2. Mel level was unchanged on exposure to E2 during the investigated phases, and its role in determining a time frame for spawning in both sexes of round goby seems to be stable in those conditions. T4 and sex steroids (E2 and 11-KT) were sensitive to the exposure of E2, and those changes influence gonads by accelerating oocyte development, ovulation and regression and inhibiting spermatogenesis in this species. The results demonstrate that the physiological responses of fish in all investigated phases were altered over a short window of exposure, indicating that short-term exposure to a supraphysiological dose of E2 may impact fish in the wild. Furthermore, round goby can be recommended as a very suitable model for studying endocrine disruptors, which is sensitive to even short exposure to E2.
Asunto(s)
Estradiol , Perciformes , Animales , Estrógenos , Femenino , Peces , Gónadas , MasculinoRESUMEN
The aim of this study was to determine changes in concentrations of melatonin (Mel) and thyroxine (T4) in plasma, and 17ß-estradiol (E2) and 11-ketotestosterone (11-KT) in plasma and gonads of female and male round gobies (Neogobius melanostomus) from the Southern Baltic Sea in four phases of the reproductive cycle classified as pre-spawning, spawning, late spawning and non-spawning periods. The concentrations of Mel, T4 and E2 were determined by radioimmunoassay (RIA) whereas 11-KT was quantified using an enzyme immunoassay (EIA). The maturity stage of gonads was determined using histological analyses. The pattern of changes in Mel concentrations of females and males was similar with the greatest concentrations in the spawning and non-spawning phases. In both sexes, there was a similar tendency of change in concentrations of T4 and E2 with the increase being in the pre-spawning and non-spawning phases. The greatest concentrations of 11-KT were observed in the plasma and gonads of males during the spawning phase. In females, there were no changes in 11-KT concentrations either in plasma or gonads during all phases where quantifications occurred. This is the first study for determination of the pattern of changes in Mel and T4 concentrations as well as gonadal steroids E2 and 11-KT, supported by histological analysis of gonads, in batch spawning fish during the reproductive cycle.
Asunto(s)
Estradiol/sangre , Melatonina/sangre , Testosterona/análogos & derivados , Tiroxina/sangre , Animales , Estradiol/química , Estradiol/metabolismo , Femenino , Peces , Gónadas/química , Gónadas/metabolismo , Masculino , Melatonina/química , Melatonina/metabolismo , Reproducción/fisiología , Factores Sexuales , Testosterona/sangre , Testosterona/química , Testosterona/metabolismo , Tiroxina/química , Tiroxina/metabolismo , Factores de TiempoRESUMEN
In this in vitro gradient perfusion study, we determined whether there is a functional relationship between oestradiol and the arginine vasotocin/isotocin (AVT/IT) system in the female round goby (Neogobius melanostomus). Brain explants were perfused in medium supplemented with 17ß-oestradiol (E2) at doses mimicking the plasma levels of this hormone in nature during the spawning-capable phase and regressing phase. We aimed to establish which pathway, genomic or non-genomic, is involved in this mechanism in different reproductive phases. For this purpose, brain explants were perfused in medium supplemented with Fulvestrant (ICI 182.780) or Actinomycin D (Act D) separately or in combination with E2 The contents of AVT and IT in the perfusion media were determined using high-performance liquid chromatography (HPLC) with fluorescence and UV detection. During the spawning-capable phase, the effect of E2 on AVT release is mediated through oestrogen receptors (ERs) via both genomic and non-genomic pathways, while IT release is mediated through ERs via a genomic pathway only. In the regressing phase, release of both nonapeptides is mediated through ERs via a genomic pathway. This is the first study to present a feasible mechanism of oestradiol action on the AVT/IT system in female fish during different phases of the reproductive cycle.