An avian bioassay for environmental estrogens: the growth response of zebra finch (Taeniopygia guttata) chick oviduct to oral estrogens.
The rat uterotrophic assay is a recommended tier 1 screening assay for environmental estrogens, but no comparable assay exists for altricial birds. We orally dosed zebra finch chicks daily during their linear growth phase (days 5-11) with estradiol benzoate (EB), genistein, methoxychlor, or octylphenol, all dissolved or suspended in canola oil, or canola oil alone, as a vehicle control. On day 12, oviducts were removed, weighed and examined histologically. All doses of EB (0.1-1,000 nmol/g body wt), genistein at 100 nmol/g. and methoxychlor and octylphenol at 1,000 nmol/g, markedly increased oviduct weight, with the highest dose of EB inducing a 60-fold increase over controls. Oviducts were differentiated in a dose-depedent manner to the point of having tubular glands and a pseudostratified, ciliated epithelium at the higher doses of EB. Our earlier results show that EB at 100 and 1,000 nmol/g impairs reproductive performance of zebra finches. Thus, the zebra finch oviduct bioassay measures estrogenicity over a wide dose range and, for EB exposure, can predict impairment in adult reproductive performance. The responsiveness of chick oviducts to estrogen stimulation may serve as a useful marker of estrogen exposure in wild populations of songbirds.
Millam
James R
JR
Department of Animal Science, School of Veterinary Medicine, University of California, Davis, California 95616-8532, USA. jrmillam@ucdavis.edu
Craig-Veit
Christina B
CB
Batchelder
Marianne E
ME
Viant
Mark R
MR
Herbeck
Tina M
TM
Woods
Leslie W
LW
D000284:Administration, Oral; D000818:Animals; D001681:Biological Assay / Q000379:methods; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D010057:Oviducts / Q000196:embryology*; D011960:Receptors, Estrogen / Q000187:drug effects*; D012098:Reproduction; D020308:Songbirds
D004967:Estrogens; D011960:Receptors, Estrogen