Effects of binary mixtures of six xenobiotics on hormone concentrations and morphometric endpoints of northern bobwhite quail (Colinus virginianus)

This study investigated the effects of six endocrine disrupters in five dif ferent doses (0.1, 0.3, 1, 3, 10 mg/kg or mug/kg) in ethanol administered b y oral gavage to bobwhite quail eggs. Six eggs each were in each dose group of coumestrol, ethynyl estradiol, indole-3-carbinol, o,p ' -DDE, p,p ' -DD E, or TCDD. Eggs were also dosed in two sets. One set was ethynyl estradiol (0, 0.03, 0.1, 0.3, 1.0, 3.0, 10.0 mug/kg) and TCDD (0, 0.003, 0.01, 0.03, 0.1, 0.3 mug/kg). This set was dosed below the air cell with corn oil as v ehicle. Also, northern bobwhite quail eggs were injected in ovo with nine b inary mixtures of six xenobiotics prior to incubation (coumestrol (0.3 mg/k g), ethynyl estradiol (3.0 mug/kg), indole-3-carbinol (3.0 mg/kg), o,p ' -D DE (1.0 mg/kg), p,p ' -DDE (1.0 mg/kg), TCDD (0.1 mug/kg)). The mixtures in jected were p,p ' -DDE+indole-3-carbinol, coumestrol+indole-3-carbinol, TCD D+indole-3-carbinol, p,p ' -DDE+o,p'-DDE, p,p ' -DDE+ethynyl estradiol, cou mestrol+ethynyl estradiol, coumestrol+TCDD, o,p ' -DDE+ethynyl estradiol, T CDD+ethynyl estradiol. Eggs were dosed once prior to initiating incubation. Quail were allowed to hatch and were sacrificed at 21 days of age. Blood, measurements, and tissues were collected. Survival was significantly affect ed by increasing concentrations of TCDD in ethanol as revealed by trend ana lysis. Survival was also affected significantly by o,p ' -DDE in ethanol bu t not by trend. Survival results of mixtures indicate significant differenc es among mixture, mixture components, and controls for coumestrol+TCDD, eth ynyl estradiol+TCDD, and indole-3-carbinol+TCDD. Some trends from doses of single com pounds that are supported by results in the literature were obse rved for hatchling weight of ethynyl estradiol dosed females, weight gain o f indole-3-carbinol dosed males, weight gain and liver somatic index of o,p ' -DDE dosed males, spleen somatic index of TCDD dosed males, and weight g ain, gonad somatic index and egg gland somatic index of TCDD dosed females. In conclusion, the dose-response treatments appeared to have effects beyon d effects on survival of in ovo dosed quail. For mixtures,plasma estradiol concentrations were significantly different among coumestrol+ethynyl estrad iol, ethynyl estradiol, coumestrol, and vehicle treatments. Liver somatic i ndex among the same treatments was also significantly different. Kidney som atic index among ethynyl estradiol+p,p ' -DDE, ethynyl estradiol, p,p ' -DD E, and vehicle treatments was significantly different. Plasma estradiol and plasma testosterone ratios were very different among o,p ' -DDE+p,p ' -DDE , o,p ' -DDE, p,p ' -DDE, and vehicle treatments. Coumestrol and ethynyl es tradiol appear antagonistic for plasma estradiol concentrations and liver s omatic index when both chemicals are present together. Ethynyl estradiol an d p,p ' -DDE appear to act additively on kidney somatic index when combined together. Mixtures of compounds used in this study indicate effects very d ifferent from either or both mixture components, indicating the lack of pre dictability of chemicals when combined in mixtures. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.