ICI 182,780 has agonistic effects and synergizes with estradiol-17 beta in fish liver, but not in testis

BACKGROUND: ICI 182,780 (ICI) belongs to a new class of antiestrogens developed to be pure estrogen antagonists and, in addition to its therapeutic use, it has been used to knock-out estrogen and estrogen receptor (ER) actions in several mammalian species. In the present study, the effects and mechanism of action of ICI were investigated in the teleost fish, sea bream (Sparus auratus). METHODS: Three independent in vivo experiments were performed in which mature male tilapia (Oreochromis mossambicus) or sea bream received intra-peritoneal implants containing estradiol-17 beta (E2), ICI or a combination of both compounds. The effects of E2 and ICI on plasma calcium levels were measured and hepatic and testicular gene expression of the three ER subtypes, ER alpha, ER beta a and ER beta b, and the estrogen-responsive genes, vitellogenin II and choriogenin L, were analyzed by semi-quantitative RT-PCR in sea bream. RESULTS: E2 treatment caused an increase in calcium levels in tilapia, while ICI alone had no noticeable effect, as expected. However, pretreatment with ICI synergistically potentiated the effect of E2 on plasma calcium in both species. ICI mimicked some E2 actions in gene expression in sea bream liver upregulating ER alpha, vitellogenin II and choriogenin L, although, unlike E2, it did not downregulate ER beta a and ER beta b. In contrast, no effects of E2 or ICI alone were detected in the expression of ERs in testis, while vitellogenin II and choriogenin L were upregulated by E2 but not ICI. Finally, pretreatment with ICI had a synergistic effect on the hepatic E2 down-regulation of ER beta b, but apparently blocked the ER alpha up-regulation by E2. CONCLUSION: These results demonstrate that ICI has agonistic effects on several typical estrogenic responses in fish, but its actions are tissue-specific. The mechanisms for the ICI agonistic activity are still unknown; although the ICI induced up-regulation of ER alpha mRNA could be one of the factors contributing to the cellular response

Hormonal control of sexual differentiation and reversal in sea bream sparus aurata (L.)

Tese de Doutoramento, Biologia Marinha, Unidade de Ciências e Tecnologias dos Recursos Aquáticos, Universidade do Algarve, 2001A dourada, Sparus aurata, é um peixe hermafrodita protândrico, i.e, atinge a primeira maturação sexual como macho podendo inverter o seu sexo para fêmea nas épocas de reprodução subsequentes. O fenómeno, designado como inversão sexual, sendo bastante comum nos teleósteos em geral, é ainda mal conhecido, sobretudo do ponto de vista genético e fisiológico (desconhecem-se, nomeadamente, quais e como se relacionam as moléculas indutoras e mediadoras do processo)

The effect of estrogen on the gnads and on in vitro conversion of androstenedione to testosterone, 11-ketotestosterone, and estradiol-17ß in Sparus aurata (Teleostei, Sparidae)

The effects of estrogen on gonad morphology and steroidogenesis of sea bream, Sparus aurata, a protandrous hermaphrodite teleost, were investigated. Fish were treated in winter/spring for different periods with 17aethynylestradiol (ethE2; experiment 1) and in summer with two doses of estradiol-17b (E2; experiment 2). Estrogen was more effective in summer. Its main effect on the gonad was inhibition of testicular growth and of male germ cell development beyond the spermatogonia stage, including mitosis. The effect of estrogen on ovarian development was slight and only apparent at the end of experiment 2 in the higher dose group. Gonadal fragments were incubated at different times during treatment with androstenedione and the output of testosterone (T), estradiol (E2), and 11-ketotestosterone (11KT) was measured by radioimmunoassay. T and E2 production was inversely correlated with the proportion of testicular tissue (and positively with ovarian tissue) in the gonad in experiment 2. However, the production of 11KT was not correlated with any type of tissue, possibly because of further metabolism. Inhibition of testicular development by estrogen was also associated with higher output of steroid conjugates

Gonadal steroidogenesis in response to estradiol-17ß administration in the sea bream (Sparus aurata L.)

The sea bream (Sparus aurata) is a protandrous hermaphrodite teleost fish in which estrogen administration induces testicular regression without influencing ovarian development. To analyze the changes in steroidogenesis of fish treated with two levels of estrogen (2 and 10 mg z kg21) and untreated control fish, fragments of gonads were incubated with tritiated 17-hydroxyprogesterone and the metabolites identified. The ability to extract radioactivity decreased with incubation time and was lower in gonads containing a larger proportion of ovarian tissue. The difference in steroidogenic capacity between control and estrogen-treated groups was generally quantitative rather than qualitative and paralleled the observed histological changes. The same metabolites were identified in all three groups, but estrogen treatment caused a marked inhibition of 5b-reduction, 3a-reduction, side-chain cleavage, and 11b-hydroxylation. The main androgens identified were 11b-hydroxy-4-androstene-3,17-dione and 3a-hydroxy-5b-androstane-3,17-dione, and the synthesis of both steroids was inhibited by estrogen treatment. Of the more polar pregnanes, 5bpregnane-3a,17,20a-triol and 5b-pregnane-3a,17,20btriol were detected in significant amounts, but only the latter appeared to be associated with development of the testis (in the untreated fish). A feature of sea bream gonadal steroidogenesis less common in other teleosts was the presence of 6a- and 6b-hydroxylation

The effect of stocking density on growth in the gilthead sea-bream, Sparus aurata (L.)

The effect of stocking density on growth and size variability in gilthean sea-bream, Sprus aurata (L.) was tested by growing juveniles at densities of 0,35 kg m3, 1,3 kg m3 and 3,2 kg m3