Residues of human pharmaceuticals, such as β-blockers are increasingly found in effluent wastewater of treatment plants (WWTP) and represent a potential environmental threat. Beta-blockers antagonize β-adrenergic receptors and thereby control hypertension and cardiac arrhythmias. The amino acid sequence of the target, the β1-adrenergic receptor, is evolutionarily highly conserved among vertebrates. Thus, organisms may physiologically respond to β-blockers. For environmental risk assessment one has to know the extent to which aquatic organisms are exposed to β-blockers and metabolites with the same mode of action (MOA).
The mode of action-based β-blocker assay in living cells measures total β-blocker activities in complex mixtures such as WWTP effluents as equivalents of the lead substance metoprolol (MetEQ). The assay is suitable as a standard method in large-scale monitoring of WWTP effluents and the aquatic environment they are discharged into. The CLARIOstar® microplate reader provides highly stable and reliable results as well as the required robustness for continuous use.