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EFFECTS OF THE ANDROGENIC GROWTH PROMOTER 17-β TRENBOLONE ON FECUNDITY AND REPRODUCTIVE ENDROCRINOLOGY OF THE FATHEAD MINNOW
Citation:
Ankley, G T., K M. Jensen, E A. Makynen, M D. Kahl, J J. Korte, M. W. Hornung, T. M. Henry, J. S. Denny, R. L. Leino, V S. Wilson, M C. Cardon, P C. Hartig, AND L. E. Gray Jr. EFFECTS OF THE ANDROGENIC GROWTH PROMOTER 17-β TRENBOLONE ON FECUNDITY AND REPRODUCTIVE ENDROCRINOLOGY OF THE FATHEAD MINNOW. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. SETAC Press, Pensacola, FL, 22(6):1350-1360, (2003).
Description:
Trenbolone acetate is a synthetic steroid which is extensively used in the U.S. as a growth promoter in beef cattle. The acetate is administered to livestock via slow release implants; some is converted by the animal to 17-β trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-B trenbolone is comparatively stable in animal 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 17-B trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas). Male and female fish were exposed for 21 d to nominal (target) concentrations of the test chemical ranging from 0.005 to 50 ug/L. Fecundity of the fish was significantly reduced by exposure to 17-B trenbolone at measured test concentrations of _> 0.027 ug/L. The 17-B trenbolone was clearly androgenic in the fish at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steriod and vitellogenin concentrations in the females were significantly reduced by exposure to the androgen; based on trends in concentration response relationships, there was some indication that these parameters may have been affected at the lowest 17-B trenbolone concentration tested, approximately 0.0015 ug/L (measured). The androgen also altered reproductive physiology of male fathead minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 41 ug 17-B trenbolone/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and elevated concentrations of estradiol and vitellogenin. Competitive binding assays suggested that one possible explanation for elevated vitellogenin in the males could be due to activation of the fathead minnow estrogen receptor at relatively high concentrations of the 17-B trenbolone.