Ws. Baldwin et al., METABOLIC ANDROGENIZATION OF FEMALE DAPHNIA-MAGNA BY THE XENOESTROGEN4-NONYLPHENOL, Environmental toxicology and chemistry, 16(9), 1997, pp. 1905-1911
Vertebrates and invertebrates metabolize testosterone to a variety of
less-polar derivatives that elicit varying degrees of androgenicity as
well as polar elimination products. We have developed a model, using
the cladoceran Daphnia magna, with which the ability of xenobiotics to
alter steroid hormone metabolism can be assessed and possible physiol
ogic consequences evaluated during a 3-week assay. This model was used
to assess the effects of the xenoestrogen 4-nonylphenol on steroid-me
tabolic processes. Exposure of daphnids to 100 mu g/L 4-nonylphenol fo
r 48 h caused a significant increase in the accumulation of radioactiv
ity derived from [C-14]testosterone provided to the exposure media. Mo
re definitive analyses demonstrated that both 25 and 100 mu g/L 4-nony
lphenol disrupted components of the testosterone metabolic pathway tha
t would lead to a decrease in the metabolic elimination of testosteron
e and an increase in the accumulation of androgenic derivatives. Expos
ure of daphnids to 100 mu g/L 4-nonylphenol significantly decreased fe
cundity of the organisms while having no effect on survival of the par
ental organisms. Comparison of metabolic and reproductive effects of L
C-nonylphenol revealed that 71 mu g/L, the reproductive chronic value,
would reduce the metabolic elimination of testosterone by approximate
ly 50%. This relationship is consistent with that which we have report
ed for other toxicants and identifies a mechanism, in addition to estr
ogenicity, that may contribute to the reproductive toxicity of this co
mpound.