PH01 Endocrine Disruption
Exhibit Hall
8:00 AM - Thursday, 13 November 2003
(PH013) Endocrine Endpoints Evaluated During An OECD One Generation Avian Reproduction Study.
Stafford, J.1, Brewer, L.1, Hunt, K.2, 1 Springborn Smithers Laboratories, Snow Camp, NC, USA2 Univeristy of Washingoton, Seattle, WA, USA
ABSTRACT- Four Endocrine endpoints were added to a single generation avian reproduction study conducted according to OECD draft guideline (dated April 2000) for a one-generation reproduction study, which calls for exposing Japanese quail (Coturnix coturnix japonica)to the test substance via feed for 6 weeks after two weeks of egg production on clean feed. The objective of the study was to evaluate the chosen endocrine endpoints for their potential for identifying endocrine effects during a one-generation study. The endpoints added to the study were 1) measurement of excreted steroid hormones, 2) measurement of egg yolk estrogen levels, 3) oviduct growth and development in 14-day hatchlings exposed to the test substance post-hatch and 4) circulating estrogen and testosterone levels. The test substance, methoxycholor (MXC), was mixed into feed at 0, 5, 20, 80 and 320 ppm. Treated feed was fed ad libitum for 6 weeks following the first two weeks of egg production. MXC suppressed estrogen levels in fecal/urate/urine samples collected at three-day intervals from breeding pairs. However, excreted testosterone levels seemed unaffected by the MXC. Egg yolk estrogen was highly variable over time in all groups and was not significantly different among groups over time. Chick oviduct weight increased modestly, but did not show a clear dose-response relationship. Body weight of MXC-exposed chicks increased at all exposure levels except 300 ppm at which, chick body weights were reduced. Mean blood estradiol and testosterone levels were not significantly different at three time points: ng acclimation, lights up and test termination. Monitoring excreted hormone levels and 14-day oviduct and body weights in combination appear to be the most sensitive endpoints in this study. However, the data indicate that MXC is either a very week estrogen or not estrogenic at all. These endpoints should be tested with a compound that produces stronger estrogenic effects before conclusions are made about their value as detectors of endocrine effects.
Key words: Methoxychlor, Endocrine, oviduct, fecal/urates