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TWENTY WEEK EXPOSURES TO THE DRINKING WATER DISINFECTION BY-PRODUCT DIBROMOACETIC ACID: REPRODUCTIVE CYCLICITY AND STEROID CONCENTRATIONS IN THE FEMALE SPRAGUE-DAWLEY RAT
Murr, A S. AND J M. Goldman. TWENTY WEEK EXPOSURES TO THE DRINKING WATER DISINFECTION BY-PRODUCT DIBROMOACETIC ACID: REPRODUCTIVE CYCLICITY AND STEROID CONCENTRATIONS IN THE FEMALE SPRAGUE-DAWLEY RAT. Elsevier Inc. (ed.), REPRODUCTIVE TOXICOLOGY. Elsevier Science Ltd, New York, NY, 20(1):73-80, (2005).
Elevated gavage exposures to the drinking water disinfection by-product dibromoacetic acid (DBA) have been found to disrupt estrous cyclicity in the rat and induce increases in estradiol concentrations in both cycling (day of estrus) and ovariectomized/estradiol-implanted females. The present study was designed to investigate both effects in Sprague-Dawley rats following an extended 20 week treatment with lower dosages of DBA administered in the drinking water (calculated mean intake concentrations of 5, 16 and 33 mg/kg/d). No treatment-related effects on cyclicity were present, although elevations in serum estradiol on the day of vaginal estrus were noted in regularly cycling rats when assessed at the 3rd and 8th weeks of exposure. By the 19th week, this effect was no longer present cycling animals, but its absence was attributable to a marked increase in control estradiol concentrations, which may be associated with endocrine alterations that precede a disruption in estrous cyclicity in middle-aged females. On diestrus at the 20th week, estrone levels were increased at all dosages, although no effects were present in serum androstenedione or progesterone. Uterine and pituitary weights were unchanged at this time, although the small number of rats in persistent estrus (PE) did show a dose-related increase in pituitary weight, possibly reflecting an added layering of treatment on the PE-associated rise in estradiol normally seen in these females. The results indicate that the increases in circulating estradiol from drinking water exposures to DBA were not able to cause a premature disruption of estrous cyclicity in this moderately estrogen-sensitive rat strain.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB
REPRODUCTIVE TOXICOLOGY DIVISION