Selected biomarkers of the effects of veterinary growth stimulants on Clarias gariepinus

• Main Author: Alexandre, Marco Paulo
• Published: 2011
• Subjects: Clarias gariepinus; Hormones - Physiological effects; Somatotropin - Physiological effects
• Online Access: http://hdl.handle.net/10210/3727

M.Sc. === There has been an increasing concern worldwide regarding the possible adverse effects of pharmaceutical supplements present in our aquatic ecosystems and whether or not they modify or alter physiological functioning in humans and wildlife. Trenbolone acetate (TBA) for example, is a commonly used androgenic anabolic steroid used in the production of cattle. TBA is metabolized into trenbolone-β and excreted as both trenbolone-α and -β. In liquid manure trenbolone-β has a half-life of over 270 days. Therefore if released into the surrounding environment there could be severe ecological impacts. The aim of this study was to determine the physiological effects of hormones used as growth stimulants in cattle production on the Sharptooth Catfish - Clarias gariepinus. The growth stimulants assessed in this study included; Trenbolone acetate, Methyltestosterone, Diethylstilbestrol and Zeranol. The aim was pursued with the use of three biomarker assays - Glutathione-S-transferase (GST), Uridine-Diphosphate Glucuronosyltransferase (UDPGT) and Cellular Energy Allocation (CEA). Fish were exposed under controlled conditions for a period of 5, ten and 15 days respectively using a flow-through system. Testes were removed and standard histological techniques were employed. Selected target organs were removed and immediately frozen in liquid nitrogen and stored at -80°C until needed for biomarker analysis.The results obtained from the gonado-somatic Index (GSI) showed that there were no significant differences (p<0.05). The hepato-somatic index (HSI) increased throughout all the different exposure groups. The histological assessment showed no significant alterations in the cell structure of the testes. With regards to the biomarkers used, CEA reflected changes in both the energy available and the energy consumed by the test organisms during the exposures. A common trend was observed throughout the different exposures. A change would occur after the ten day exposure period however a recovery would be made after 15 days of exposure. Both GST and UDPGT reflected increased activity in the liver with GST reflecting a significant difference (p<0.05) between the control and the exposure groups, however GST activity in the kidneys were not affected. To conclude, further studies will be needed to determine whether or not these growth stimulants will have a significant effect at higher concentrations and over longer exposure periods.