PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P538) Reproductive Toxicity of Androgenic Growth Promoters in the Fathead Minnow.

Jensen, Kathleen^*,1, Kahl, Michael¹, Makynen, Elizabeth¹, Hornung, Michael¹, Ankley, Gerald¹, ¹ U.S. Environmental Protection Agency, Duluth, MN, USA

ABSTRACT- Trenbolone acetate is a synthetic steroid which is extensively used in the US as a growth promoter in beef production. The acetate is administered to livestock via slow release implants; it is converted by the animal to -trenbolone, a relatively potent androgen receptor agonist. Both -trenbolone and it's stereoisomer, -trenbolone, are significant excretory products from beef cattle. Recent studies indicate they are comparatively stable in waste, suggesting the potential for exposure to aquatic animals via direct discharge and/or run-off. Little is known, however, concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of - and -trenbolone on reproductive endocrinology in the fathead minnow. Male and female fish were exposed for 21-d to graded concentrations of the test chemicals ranging from 0.005 to 50 ug/l (-trenbolone) or 175 to 7000 ug/l (-trenbolone). Both compounds were highly androgenic in the fish, as evidenced by the de novo production in females of dorsal tubercles, structures normally present only in mature males. Fecundity also was significantly affected by the two androgens, with a measured no-observable effect concentration for -trenbolone on the order of 0.0012 ug/l. The potential effects of these chemicals on animals exposed to feedlot wastes currently are unknown, but warrant further investigation. This abstract does not affect EPA policy.

Key words: endocrine disruptors, trenbolone, fathead minnow, reproduction