Developmental expression and estrogen responses of endocrine genes in juvenile yellow perch (Perca flavescens).

The present study examines the expression of growth-regulating genes (gh, prl, smtl and igf1b), the estrogen receptors (esr1 and esr2a) and aromatase (cyp19a1a) in developing yellow perch. To gain an initial understanding into the endocrine control of growth preceding and involved with sexual size dimorphism (SSD), where females have been reported to grow faster and larger than males, young of the year fish were sampled for length, weight and tissues at several time points (102-421 days post-hatch (dph)). Positive growth was seen in both sexes over the sampling interval, but SSD was not manifested. Using real-time quantitative PCR, we found that pituitary growth hormone (gh) and liver insulin-like growth factor-1b (igf1b) mRNA levels were significantly affected by dph and levels were found to be correlated with growth in both sexes. Liver cyp19a1a, esr1 and esr2a mRNA levels were significantly influenced by dph, whereas there was a significant dph*sex interaction on liver esr2a mRNA levels with males having higher levels than females at 379 and 421 dph. Ovarian cyp19a1a decreased with dph, but there were no changes in esr1 or esr2a mRNA levels. Dietary treatment of juvenile (∼300 dph) females with 20 mg/kg diet 17ß-estradiol resulted in significantly higher liver esr1 mRNA levels and a sustained hepatosomatic index (I(H)). Across all data sets liver esr2a mRNA levels showed the most significant positive correlation with liver igf1b mRNA levels. These findings show that growth is accompanied by increases in pituitary gh, liver igf1b and liver esr1 and esr2a mRNAs in juvenile yellow perch.

Effects of xenobiotics and steroids on renal and hepatic estrogen metabolism in lake trout.

Experiments were conducted to (1) elucidate the biochemical pathways of E2 metabolism in the lake trout (Salvelinus namaycush) kidney and liver, and (2) test the hypothesis that specific xenobiotics and endogenous steroids inhibit E2 metabolism by these tissues. Kidney and liver tissue fragments from immature lake trout were incubated in vitro in the presence of radiolabelled E2 plus various xenobiotics or steroids. E2 metabolites were identified by liquid chromatography/mass spectroscopy, and quantified by liquid scintillation spectroscopy. A major metabolite produced by both tissues was an unidentified hydroxylated estrogen metabolite (E2-OH) with a molecular mass of 288 that was not estriol (16-OH-E2), but possibly 7alpha-OH-E2 or 2-OH-E2 (catecholestrogen). Both tissues also produced estradiol-17-glucuronide (E2-17-G), estradiol-17-sulfate (E2-17-S), and estradiol-3-glucuronide (E2-3-G). Compared to the kidney, the liver produced half the amount of conjugated metabolites, but twofold more E2-OH. The following xenobiotics (at a concentration of 100 microM) inhibited the production of water-soluble (i.e., conjugated) E2 metabolites by both the kidney and liver: 4,4'-(OH)2-3,3',5,5'- tetrachlorobiphenyl (4,4'-OH-TCB), bisphenol A (BPA), tetrabromobisphenol A (TB-BPA), tetrachlorobisphenol A (TC-BPA), tribromophenol (TBP), trichlorophenol (TCP), and pentachlorophenol (PCP). The alkylphenols, 4-n-nonylphenol (NP), and 4-octylphenol (OP), and 2,2',4,4'-tetrabromodiphenyl ether (TBDE) had no significant effect on E2 metabolism by either tissue. Testosterone and 17alpha,20beta-dihydroxy-4-pregnen-3-one inhibited the production of conjugated E2 metabolites by both the kidney and liver. Cortisol and 11-ketotestosterone inhibited E2 metabolism by the liver only. The median inhibitory concentrations (IC50) for 4,4'-OH-TCB ranged from 7-32 microM in the kidney and 0.6-1.6 microM in the liver. For BPA, IC50's ranged from 40-108 microM in the kidney and 11-18 microM in the liver. Low doses (0.1 microM) of 4,4'-OH-TCB and BPA significantly increased estrogen metabolism in the kidney. The results suggest that certain estrogenic xenobiotics and endogenous steroids may inhibit the phase II conjugation of E2 by the kidney and liver of lake trout, and some of the known biological effects of these compounds are likely mediated, at least partially, by this mechanism of action.

Influence of dietary genistein levels on tissue genistein deposition and on the physical, chemical, and sensory quality of rainbow trout, Oncorhynchus mykiss.

Genistein, the primary isoflavone in soybean, is one of the chemical components responsible for some of the off-flavors associated with soy-based foods. The potential effects of genistein on the sensory and chemical quality of fish muscle may affect the full utilization of soybean meal as an alternative protein in aquaculture diets. Fingerling trout fed commercial diets containing 0, 500, 1000, or 3000 ppm pure genistein were analyzed after 6 and 12 months of feeding. Genistein was extracted by enzymatic digestions in Tris buffer and quantified by high-performance liquid chromatography. Moisture, fat, protein, ash, and tristimulus color of the fillets were determined. The extent of lipid oxidation occurring in fillets harvested after 12 months of feeding was studied by measurements of thiobarbituric acid reactive substances (TBARS) after 4 and 8 days of refrigerated storage at 4 degrees C. Triangle tests were performed to determine if there were any detectable sensory differences. A dietary genistein content of 3000 ppm led to the deposition of approximately 5.4 pmol of genistein/mg of fillet. Triangle test panelists were unable to detect any significant (p < or = 0.05) differences between the fillets from trout fed the 0 and 3000 ppm genistein concentrations. Moisture, ash, and protein content were influenced by time of harvest, while color was unaffected. TBARS levels on days 4 and 8 were significantly (p < 0.05) higher in the fillets from the 0 ppm genistein level than in fillets from fish fed dietary genistein.