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Regular Article |
a Department of Urology (M/C 955), College of Medicine, University of Illinois, Chicago, Illinois 60612-7310
b Department of Environmental & Molecular Toxicology, North Carolina State University, Raleigh, North Carolina 27695-7633
c Endocrinology Branch, Reproductive Toxicology Division, National Health and Environment Effects Research Laboratory MD72, United States Environmental Protection Agency, Durham, North Carolina 27713
ABSTRACT
Environmental contaminants with estrogenic properties have been cause for heightened concern about their possible role in inducing adverse health effects. Brief exposure of rodents to high doses of natural estrogens early in life results in permanent alterations of the male reproductive tissues, but the question of whether environmentally relevant doses can cause the same effects remains controversial. The current project was designed to determine the dose-response relationship between neonatal estradiol exposure and the development of the male reproductive tract in the rat. Neonatal male Sprague-Dawley (SD) and Fisher 344 (F344) rats were exposed to ß-estradiol-3-benzoate (EB) at concentrations ranging from 0.015 µg/kg body weight (BW) to 15.0 mg/kg BW and 0.15 µg/kg BW to 1.5 mg/kg BW, respectively. Results showed an inverted U-shaped dose-response profile for testis and epididymis weights in 35-day-old SD rats, with increased organ sizes at the low-dose end of the treatment. This effect was transient and was not sustained into adulthood. Increased hepatic testosterone hydroxylase activities in low-dose animals suggest an advancement of puberty as the cause for increased reproductive organ weights. On postnatal day (PND) 90, a stimulatory low-dose response to EB was present in SD rat testicular and epididymal weights, however at one order of magnitude lower dose than that seen on PND 35, suggesting a separate effect. All SD male reproductive tract organs and serum hormones showed a permanent inhibitory response to high doses of neonatal EB. F344 rats exhibited greater estrogen sensitivity on PND 90. Despite this heightened responsiveness, F344 rats did not exhibit a low-dose effect for any endpoint. These low-dose responses to estradiol are organ and strain specific.
1 Supported by EPA STAR grant R826299 to G.S.P.
2 Correspondence: Gail S. Prins, Department of Urology (M/C 955), University of Illinois, 820 South Wood Street, Chicago, IL 60612-7310. FAX: 312 996 1291; gprins{at}uic.edu
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