In Joon Hwang

Effects of nonylphenol and 3,3′,4,4′,5-pentachlorobiphenyl on in vitro oocyte steroidogenesis in redlip mullet, Chelon haematocheilus

We investigated the in vitro effects of nonylphenol (NP) and 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) on steroidogenesis in redlip mullet, Chelon haematocheilus, oocytes. In experiment 1, we investigated the effects of NP and PCB126 on steroid production from exogenous steroid precursors. Vitellogenic oocytes (0.75 mm in diameter) were incubated with 10 and 100 ng/ml NP or PCB126 with [3H]17α-hydroxyprogesterone as a precursor. The major metabolites produced were androstenedione, testosterone (T), estrone, and estradiol-17β (E2). Both NP and PCB126 increased T production and decreased E2 production, except for 100 ng/ml PCB126. In experiment 2, oocytes (0.65–0.75 mm in diameter) were exposed to NP and PCB126 at different concentrations (0.01, 0.1, 1, 10, and 100 ng/mL). After the incubation, T and E2 production was measured by radioimmunoassay. NP inhibited E2 production at concentrations of 0.01 and 0.1 ng/ml in 0.75-mm-diameter oocytes. NP at 1 and 100 ng/mL stimulated T production, but had no observable effect on E2 production. PCB126 treatment did not affect E2 production at any of the concentrations tested. NP alone at 0.1 ng/mL resulted in a significant decrease in E2 production in 0.65-mm-diameter oocytes. PCB126 did not show any significant effects on either T or E2 production at all concentrations tested. These results suggest that NP acts like an antiestrogen at lower concentrations (0.01–0.1 ng/ml) in vitellogenic oocytes of redlip mullet.

Changes in Plasma Sex Steroid and Cortisol Levels during Annual Reproductive Cycle of Ribbed Gunnel, Dictyosoma burgeri

We investigated the changes in plasma sex steroid hormones, testosterone (T), estradiol-17β (E2), 17,20β -dihydroxy-4-pregnen-3-one (17α20βP), 11-ketotestosterone (11KT) and cortisol levels from ribbed gunnel, Dictyosoma burgeri in associated with annual reproductive cycle. The gonadosomatic index (GSI) of females increased from November, peaked in February and decreased rapidly from March. The GSI of males also increased from November, peaked in January and then decreased gradually. In females, E2 levels increased and remained high from December to February. The levels of T showed a similar tendency and correlated (rs=0.898, p<0.01) with E2 levels. The levels of 17α20βP increased rapidly in February (4.78±1.01 ng/ml) and peaked in July (5.08±0.65 ng/ml). Cortisol level was peaked in March and correlated with 17α20βP levels (rs=0.696, p<0.01). In males, the levels of T was peaked in January and then decreased rapidly. The levels of 11KT were remained high from October to January. On the other hand, the levels of 17α20βP fluctuated during reproductive cycle. These results suggest that plasma sex steroids in ribbed gunnels have annual periodicity, and that cortisol may involve in maturation of females.

Estrogenicity of 4-nonylphenol and diethylstilbestrol on in vitro oocyte maturation of the dusky tripletooth goby, Tridentiger obscurus

Abstract This study investigated the estrogenicity of 4-nonylphenol (NP) and diethylstilbestrol (DES) in vitro during oocyte maturation in the marine fish, Tridentiger obscurus, using steroid hormone assays and GVBD assay. Vitellogenic (0.53 mm diameter) and fully vitellogenic (0.75 mm diameter) oocytes were in vitro exposed to NP (0.045–453.82 nM) and DES (0.037–372.62 nM). In vitellogenic oocytes, 45.38 and 453.82 nM NP and 3.73–372.62 nM DES increased the estradiol-17β (E2)/testosterone (T) ratio. In fully vitellogenic oocytes, 0.45, 45.38 and 453.82 nM NP and 3.73 nM DES increased E2/T. In the GVBD assay, 0.45 and 4.54 nM NP and 0.037, 3.73 and 37.26 nM DES inhibited GVBD. These results suggest that NP and DES have estrogen-agonistic effects in oocyte maturation in T. obscurus. In addition, NP and DES have different sensitivity according to the oocyte developmental stage, and the estrogen-agonistic effects of DES were greater than were those of NP.