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1.
Environ Toxicol Chem ; 26(5): 927-34, 2007 May.
Article in English | MEDLINE | ID: mdl-17521139

ABSTRACT

Two studies investigated the accumulation and reproductive effects of p,p'-dichlorodiphenyldichloroethane (DDE) and dieldrin over 30 or 120 d of oral exposure in captive Florida, USA, largemouth bass (Micropterus salmoides floridanus). The 30-d exposures were conducted during the peak reproductive season, and the 120-d study was conducted to simulate exposure throughout the ovarian cycle. Whole body chemical residue concentrations were similar, regardless of exposure duration, for the medium and high feed concentrations of either chemical; however, the low-dose residue concentrations were much lower, yet similar to natural exposures. No clear dose-response relationships were identified between chemical dose and morphological (length, weight, hepatosomatic index) or reproductive endpoints (sex steroid concentration, gonadosomatic index, percentage of fry hatching). Reproductive parameters were variable within treatment groups, indicating that circulating sex steroids and percent hatch endpoints have high natural variability among fish of the same age and reproductive stage. However, in general there was a decrease in plasma estradiol and 11-ketotestosterone for female and male fish, respectively, that were exposed to dieldrin. Overall, results suggest that exposure throughout ovarian (follicular) development to either DDE or dieldrin alone does not result in the depressed endocrine status and poor reproductive success reported in highly organochlorine pesticide-contaminated environments in Central Florida, USA.


Subject(s)
Bass/physiology , Dichlorodiphenyldichloroethane/toxicity , Dieldrin/toxicity , Pesticides/toxicity , Reproduction/drug effects , Water Pollutants, Chemical/toxicity , Animals , Biomarkers/analysis , Body Size , Body Weight , Dose-Response Relationship, Drug , Female , Florida , Gonads/metabolism , Liver/metabolism , Male , Reproduction/physiology , Seasons , Steroids/blood , Time Factors
2.
Aquat Toxicol ; 78(4): 358-69, 2006 Jul 20.
Article in English | MEDLINE | ID: mdl-16765462

ABSTRACT

Dieldrin and p,p'-DDE are ubiquitous contaminants known to act as endocrine disruptors, causing impaired development and reproduction in fish and wildlife. In order to elucidate the mechanisms by which dieldrin and p,p'-DDE cause endocrine disruption in largemouth bass (Micropterus salmoides), fish were exposed subchronically through the diet to both contaminants. Following 120 days of exposure, p,p'-DDE decreased estradiol in females, but increased 11-ketotestosterone in both sexes. Dieldrin on the other hand, decreased estradiol and 11-ketotestosterone in both sexes. Both pesticides also altered steady state mRNA expression levels of a set of genes chosen to represent three possible mechanisms of endocrine disruption: (1) direct interaction with soluble sex steroid receptors, (2) biosynthesis of endogenous sex hormones, and (3) metabolism of endogenous hormones. p,p'-DDE acted as a weak estrogen, increasing the expression of vitellogenin and estrogen receptor alpha in the liver. p,p'-DDE also altered the expression of genes involved in the synthesis of endogenous hormones as well as their metabolism. Dieldrin, on the other hand, only altered expression of vitellogenin and not estrogen receptor alpha. Dieldrin also altered the expression of genes involved in hormone synthesis and metabolism, and it dramatically lowered plasma hormone levels. Both pesticides targeted expression of genes involved in all three modes of action, suggesting that they each have multiple modes of action.


Subject(s)
Bass/physiology , Dichlorodiphenyl Dichloroethylene/toxicity , Dieldrin/toxicity , Endocrine Disruptors/toxicity , Pesticides/toxicity , Animals , Bass/genetics , Bass/metabolism , Cytochrome P-450 Enzyme System/biosynthesis , Cytochrome P-450 Enzyme System/genetics , Dichlorodiphenyl Dichloroethylene/pharmacokinetics , Dieldrin/pharmacokinetics , Down-Regulation/drug effects , Endocrine Disruptors/pharmacokinetics , Estradiol/blood , Female , Gene Expression/drug effects , Male , Pesticides/pharmacokinetics , Phosphoproteins/biosynthesis , Phosphoproteins/genetics , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Receptors, Estrogen/biosynthesis , Receptors, Estrogen/genetics , Receptors, Estrogen/metabolism , Reproduction/drug effects , Reproduction/genetics , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Testosterone/analogs & derivatives , Testosterone/blood , Vitellogenins/genetics , Vitellogenins/metabolism
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