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Abstract
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The present study tried to measure the formation of melanomacrophage centers (MMCs) in various organs of
male and female goldfish exposed to nonylphenol (NP) and aimed to assess its relationship with the main sexual
hormones, estrogen receptor expression, and the pigment content of the MMCs. Immature goldfish were exposed
to 10 6 and 10 7 M NP for 25 days. After obtaining blood for measuring testosterone and estrogen (E2) levels,
tissue samples were collected from various organs for histological studies, quantifying pigments using ImageJ
software and chemical analysis, and measuring ERα gene expression. Results showed that the order of forming
MMCs in various organs exposed to NP was liver > spleen > kidney, and the order of ERα gene expression was
liver > testes > spleen > kidney in the male, and liver > spleen > kidney > ovaries in the female. Among the
three pigments present in MMCs after exposure to the two doses of NP, melanin was more obvious (especially in
the liver) and increased mostly in a dose-dependent manner in both sexes (especially in the male). Chemical
analyses confirmed these results. Measurement of testosterone and E2 level in male and female goldfish showed
that NP had more effect on the concentration of these hormones in male fish, indicating more endocrinedisrupting
potential of NP against the male fish. Generally, the increase of melanin content of melanomacrophage
centers coincided with the increase of ERα gene expression and decrease of testosterone level in goldfish
after exposure to NP.
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