Detection of endocrine disrupting compounds in abiotic and biotic matrices from the Phongola floodplain using tissue culture based bio-assays

Abstract

Increasing rates of urbanization, industrialisation, population growth and agricultural demand in South Africa have considerably decreased water quality leading to different forms of water pollution, which might be the case for the Phongolo floodplain. Some compounds commonly produced synthetically or naturally pose a risk to biological and ecosystem health. Biological responses due to these compounds could be mutagenic, carcinogenic and in some cases endocrine disruptive. These endocrine disrupting compounds (EDCs) are described as an exogenous compound, or mixture of compounds/chemicals that interfere with endocrine systems in organisms. The present study screened/assessed agonistic/anti-agonistic interaction of chemicals/compounds with the ability to bind to the oestrogen receptor (ER) and the aryl hydrocarbon receptor (AhR) in the aquatic environment of the Phongolo floodplain. Three matrices, sediment, water and fish bile, were collected from sites in the protected environment of the Ndumo game reserve in KwaZulu-Natal, South Africa; the Nyamiti Pan, the Phongola River, and the Ushutu River. One site was selected from outside the borders of Ndumo, the Nomaneni Pan, in order to determine the direct influences of communities on water sources. The water samples were extracted using solid phase extraction and applicable clean-up methods. Sediment samples were extracted using accelerated solvent extraction in a dichloromethane:acetone solution. Clean-up steps involved solid phase extraction and size exclusion chromatography. Bile was liquid-liquid extracted after enzymatic hydrolysis followed by a solid phase extraction as clean-up step. These extracts were screened with the MVLN reporter gene bio-assay for both activation and inhibition of the oestrogen receptor. The sediment samples were additionally analysed using the H4IIE-luc reporter gene bio-assay to determine if these target compounds bind to the AhR. The results obtained, indicated an activation of the oestrogen receptor for sediment, water and fish bile for different seasons and at different levels. Inhibition of the ER also occurred at different sites and at different events. Some samples from the Phongolo River elicited both activation and inhibition of the same receptor. Samples from the second sampling event (wet season) caused the highest percentage of activation of the ER. There was less evidence of ligands capable of binding to the AhR and very little response by the extracts containing the more persistent AhR-ligands The aquatic habitat most affected by contamination of these compounds was the Phongolo River. Results obtained from the Nomaneni Pan were irregular probably due to being directly impaired on by surrounding rural communities. Although, this study was successful in determining the presence of EDCs, and specifically those capable of binding to the ER, in the aquatic environment of the Phongolo floodplain the identity of the compounds remain unknown. Instrumental analysis would be beneficial in determining the specific compounds responsible for disrupting the endocrine system and their concentration levels in the environment