Androgen Inhibition of Vitellogenin Gene Expression in Tilapia (Oreochromis niloticus)
| Autor: | N. B. Ramsey, S. Langley, Catherine B. Lazier, Jonathan M. Wright |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Male
medicine.medical_specialty food.ingredient medicine.drug_class Gene Expression Estrogen receptor Binding Competitive Vitellogenins Vitellogenin Endocrinology food Methyltestosterone Internal medicine medicine Animals RNA Messenger Estradiol biology Estrogen Antagonists Tilapia Radioimmunoassay Blood Proteins Blotting Northern biology.organism_classification Androgen Antiestrogen Androgen receptor Tamoxifen Oreochromis Liver Receptors Estrogen biology.protein Electrophoresis Polyacrylamide Gel Female Animal Science and Zoology |
| Zdroj: | General and Comparative Endocrinology. 104:321-329 |
| ISSN: | 0016-6480 |
| Popis: | Treatment of mature female tilapia (Oreochromis niloticus) with high levels of androgen (17 alpha-methyltestosterone, 17 alpha MT) results in a pronounced decline in plasma vitellogenin levels as determined by gel electrophoresis. Total RNA extracted from livers of treated fish and vehicle-injected controls was analyzed by Northern and slot blot hybridization using an oligonucleotide complementary to a sequence in the 3' end of tilapia vitellogenin mRNA. The probe revealed an mRNA of 6.5 kb in liver from the control mature female fish which was decreased by 85% by androgen treatment. As expected, estradiol (E2) treatment induced the 6.5-kb mRNA in mature male tilapia. The antiestrogen, tamoxifen, strongly decreased vitellogenin mRNA levels in mature females. Radioimmunoassay of serum from control and 17 alpha MT-treated female tilapia showed a marked reduction in serum E2 levels, from 11.4 +/- 2.6 ng/ml in controls to 2.2 +/- 0.13 ng/ml in treated fish. Tamoxifen, however, resulted in increased serum E2 levels, probably by blocking E2 negative feedback. The serum E2-lowering effect of 17 alpha MT suggests an inhibitory site of action on gonadotropin production at the hypothalamic-pituitary axis, possibly through an androgen receptor or through an estrogen receptor after local aromatization of 17 alpha MT. |
| Databáze: | OpenAIRE |
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