Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9478283 | Aquatic Toxicology | 2005 | 11 Pages |
Abstract
This study examined the possibility that DDT and DDE, at sub-lethal exposure levels, exert direct effects on the biotransformation of gonadal steroids by rainbow trout (Oncorhynchus mykiss) ovarian follicles and embryos. Ovarian follicles were co-incubated with DDT or DDE at 0.01 or 1 mg lâ1 to examine effects of the pesticides on basal or cAMP-activated steroidogenesis. Ovarian preparations were incubated with radiolabelled [3H]pregnenolone ([3H]P5), and the tritiated metabolites of [3H]P5 metabolism were separated using high-performance liquid chromatography (HPLC). Testosterone (T) and 17β-estradiol (E2) production were also measured using radioimmunoassay (RIA). Embryos were either exposed to the pesticides in ovo, or co-incubated in vitro with the pesticides. The effect of the pesticides on embryo steroid biotransformation was examined using a range of radioactively labelled substrates, including [3H]P5, [3H]progesterone ([3H]P4), [3H]T and [3H]E2. At the concentrations used, the pesticides had no significant effect on the relative amounts of unconjugated radiolabelled steroids formed by the biotransformation of [3H]P5 under conditions of basal or cAMP-stimulated ovarian steroidogenesis. However, DDT and DDE appeared to reduce the basal accumulation of androgen as a product of P5 biotransformation by ovarian follicles. Basal or cAMP-stimulated total estrogen production was not affected. In addition, DDT at 1 mg lâ1 and DDE at 0.01 mg lâ1 significantly increased and decreased cAMP-stimulated T accumulation, respectively. Also DDT at 0.01 mg lâ1 and DDE at 1 mg lâ1 significantly increased and decreased basal E2 accumulation, respectively. The steroid metabolites synthesized from the different substrates by embryos were essentially similar in both controls and pesticide-exposed groups, and the survival of embryos to hatch was not significantly affected by pesticide exposure, in ovo, with an approximately 90% hatchability in all treatment groups. This study suggests that although DDT and DDE may affect ovarian androgen synthesis under some conditions, under the conditions of the present study, they do not impact on overall rates of gonadal estrogen synthesis. Similarly, the pesticides do not appear to directly affect steroid biotransformation by embryos.
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Life Sciences
Agricultural and Biological Sciences
Aquatic Science
Authors
Rakpong Petkam, Rick Renaud, Lucy Lin, Herman Boermans, John Leatherland,