Ecotoxicological responses of isolated mitochondrial systems to complex effluents. Are they worthwhile?

In vitro assays with isolated rat liver mitochondria and sub-mitochondrial particles (SMP) of beef heart were compared with acute Daphnia magna test and Microtox®, in order to establish different sensitivities when exposed to complex effluents. Median effective concentration (EC50) were calculated using the probit analysis, considering several endpoints: immobilisation for D. magna assays, luminescence decrease of the marine bacterium Photobacterium phosphoreum, inhibition of succinate generated potential or the depolarisation caused by ADP addition for rat liver mitochondria by the mithocondrial transmembrane electric potential (TEP) and reduction in the amount of NADH oxidised by the electron transport system to form NAD+ in the case of the forward electron transport (FET) or the NADH amount that is reduced to NAD+ for SMP, in the case of the reverse electron transfer (RET). The TEP tests showed to be more sensitive than the others one are. The results obtained indicate the convenience of utilising in vitro systems such as the TEP or even SMP to test whole effluent ecotoxicity.