Feminisation of young males of the common carp, Cyprinus carpio, exposed to 4-tert-pentylphenol during sexual differentiation
article
In recent years, a hierarchy of techniques has become available for detecting chemicals which may cause endocrine
disruption in the aquatic environment. The molecular structure of a chemical provides a first indication about
estrogenic activity, i.e. their likelihood of interfering with the female hormone receptor. In vitro competitive binding
assays for this receptor and specific cell cultures are also used to demonstrate an estrogenic response, but this does
not adequately indicate whether the substance will cause adverse reproductive effects in an entire organism. An
elevated level of vitellogenin, a typical female lipoprotein in the plasma of male fish is an in vivo estrogen-mediated
response. However, its direct relationship to reproductive developmental effects is as yet unclear. The present study
aims at investigating this relationship for assessing endocrine disruption in fish exposed to an estrogenic substance
during relevant life stages. A monosex population of male carp, Cyprinus carpio, was exposed to 4-tert-pentylphenol
(TPP) and to 17b-estradiol as a positive control during the period of sexual differentiation, starting at 50 days post
hatch. The fish were sampled every 10 days for the histological examination of the development of the testes, i.e. the
formation of the reproductive tract, the multiplication and subsequent meiosis of the primordial germ cells, and
gametogenesis in the early gonad. At the end of the experiment, blood was extracted for the quantification of
vitellogenin by radioimmunoassays in the plasma. The average number of primordial germ cells (PGCs) per gonadal
section was significantly reduced (PB0.001) at all sampling periods in the testes of carp exposed to 17b-estradiol
(positive control). The PGCs had commenced oogenesis after 50 days exposure and developed into oocytes as in a
‘normal’ ovary. The number of PGCs in the testes of the carp exposed to TPP was reduced in a dose dependent
manner. Spermatogenesis was severely inhibited in the testes of the TPP-exposed carp, where, few oocytes were ever
observed. 20 days exposure to 17b-estradiol were sufficient to induce the formation of an oviduct instead of a male
vas deferens, whereas this occurred after 30 days in TPP-exposed carp. A dose effect relationship with TPP was
disruption in the aquatic environment. The molecular structure of a chemical provides a first indication about
estrogenic activity, i.e. their likelihood of interfering with the female hormone receptor. In vitro competitive binding
assays for this receptor and specific cell cultures are also used to demonstrate an estrogenic response, but this does
not adequately indicate whether the substance will cause adverse reproductive effects in an entire organism. An
elevated level of vitellogenin, a typical female lipoprotein in the plasma of male fish is an in vivo estrogen-mediated
response. However, its direct relationship to reproductive developmental effects is as yet unclear. The present study
aims at investigating this relationship for assessing endocrine disruption in fish exposed to an estrogenic substance
during relevant life stages. A monosex population of male carp, Cyprinus carpio, was exposed to 4-tert-pentylphenol
(TPP) and to 17b-estradiol as a positive control during the period of sexual differentiation, starting at 50 days post
hatch. The fish were sampled every 10 days for the histological examination of the development of the testes, i.e. the
formation of the reproductive tract, the multiplication and subsequent meiosis of the primordial germ cells, and
gametogenesis in the early gonad. At the end of the experiment, blood was extracted for the quantification of
vitellogenin by radioimmunoassays in the plasma. The average number of primordial germ cells (PGCs) per gonadal
section was significantly reduced (PB0.001) at all sampling periods in the testes of carp exposed to 17b-estradiol
(positive control). The PGCs had commenced oogenesis after 50 days exposure and developed into oocytes as in a
‘normal’ ovary. The number of PGCs in the testes of the carp exposed to TPP was reduced in a dose dependent
manner. Spermatogenesis was severely inhibited in the testes of the TPP-exposed carp, where, few oocytes were ever
observed. 20 days exposure to 17b-estradiol were sufficient to induce the formation of an oviduct instead of a male
vas deferens, whereas this occurred after 30 days in TPP-exposed carp. A dose effect relationship with TPP was
Topics
Endocrine disruptionEstrogenicityAlkylphenol17b-estradiolSexual differentiationVitellogenin17β-estradiolAlkylphenolEndocrine disruptionEstrogenicitySexual differentiationVitellogenin4 tert pentylphenolEstradiolEstrogenPhenol derivativeUnclassified drugVitellogeninChemical pollutantFeminizationFishPollution effectAnimal experimentAnimal tissueCarpControlled studyFeminizationHistologyMaleNonhumanPriority journalRadioimmunoassaySexual developmentSpermatogenesisCyprinus carpio
TNO Identifier
40864
Source
Aquatic Toxicology, 43, pp. 77-92.
Pages
77-92
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