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Hormonal effects of prohomones in bovines

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Hormonal effects of prohomones in bovines

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Samenvatting

Since 1988, it has been prohibited in the European Union to use hormonally active compounds in cattle fattening. Reasons for the ban on the use of these compounds are the food quality and the health risks for consumers. During livestock inspections however, the use of so called prohormones turns up more and more. Prohormones are compounds without hormonal action by themselves, but are either metabolized in vivo into hormonal active compounds, or are able to indirectly influence natural hormone levels. Screening on these compounds is difficult due to the lack of detection methods and the metabolites of these compounds are unknown. A prohormone which is suspected to be used as a growth promoter is dehydroepiandrosterone (DHEA). DHEA is a steroid which is endogenously produced in the adrenal gland, and can be converted in peripheral target tissues. Another prohormone is ipriflavone (IF). Ipriflavone is a synthetic isoflavone which has a chemical structure comparable to hormonal active isoflavones and is used in humans to increase bone mass.

In this study we will focus on the feasibility of using microarrays as a new method to screen on prohormone abuse in bovines. Secondly, we will look at the effects of prohormones on gene expression profiles. Thirdly, we will validate a previously conducted and present microarray experiment by means of realBtime RTBPCR. Finally, we made a start with testing the in vitro effects of prohormones on human liver carcinoma cell lines. Animal experiments were conducted by exposure of Frisian bovines to DHEA and IF. Seven bovines from differently conducted experiments were selected as control animals and did not receive any administration. Six animal were exposed to oral or intramuscular administrated DHEA in three separately conducted experiments. Eight animals were treated with different concententration of orally administrated IF. RNA was extracted from the treated and untreated animals, labeled with fluorescent dyes and hybridized onto bovine arrays. Data analysis was done with PCA, gene selection and pathway analysis. Real time RTBPCR was performed to validate a previously conducted microarray experiment and the present microarray experiment studying gene expression profiles in bovine blood tissue. AntiBproliferative effects of DHEA on the human liver carcinoma cell line HepG2, were measured using the dimethylthiazolBdiphenylB tetrazoliumbromide (MTT) test.

Results obtained from the first experiment concluded that no great differences are observed between DHEA treated and untreated animals in blood tissue. This experiment provided insight into the feasibility of microarrays as a screening method on prohormone. The second experiment indicated that the exposure to IF induces large differences between treated and untreated animals. The gene expression profile further exhibits prohormonal action by regulating many steroid metabolism and biosynthesis related genes. RTBPCR validated a previously conducted research to the gene expression profile in liver induced by DHEA but failed to validate the microarray study of DHEA induced gene expression in blood tissue. Finally, a setup was made for future research on in vitro effects of prohormones.

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OrganisatieHogeschool Utrecht
OpleidingBiologie en Medisch Laboratorium Onderzoek
AfdelingLife Sciences en Chemistry
PartnerRIKILT, Institute of Food Safety, Wageningen University and Research Centre
Jaar2007
TypeBachelor
TaalEngels

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