Joint toxicity of sediment-associated permethrin and cadmium to Chironomus dilutus: The role of bioavailability and enzymatic activities

Does cadmium affect the toxicokinetics of permethrin in Chironomus dilutus at sublethal level? Evidence of enzymatic activity and gene expression

“…Surprisingly, all kinetic parameters (k u , k e , t 1/2 and BCF) for permethrin in C. dilutus showed no significant difference between the two exposure scenarios ( Table 2), suggesting that the presence of cadmium had no obvious effect on the toxicokinetics of permethrin in the midges. Our previous study detected enhanced activity of metabolic enzymes in C. dilutus when adding cadmium to exposure media compared with permethrin-only at exposure concentrations which would cause lethality (Chen et al, 2015). Thus, it is reasonable to suppose that the toxicokinetics of permethrin would be influenced by cadmium.…”

“…Previous study suggested that changes in bioavailability of sediment-bound permethrin played minimal role in antagonistic interaction between cadmium and permethrin to the lethality of the midges, but rather, increased enzymatic activities in the organisms were the likely reason for the antagonism (Chen et al, 2015). Therefore, water-only exposure was conducted in the current study instead of sediment exposure to avoid the confounding influence of changing bioavailability on the toxicokinetics of permethrin in organism.…”

“…Joint toxicity between chemicals may depend on their exposure levels (Banks et al, 2003). When C. dilutus was exposed to permethrin at concentrations which caused lethality, the activities of metabolic enzymes were significantly enhanced by adding cadmium (Chen et al, 2015). In most cases in the field, however, aquatic organisms were exposed to multiple contaminants at concentrations which would not cause lethality.…”

“…Activities of two metabolic enzymes, GST and carboxylesterase (CarE), and levels of two oxidative stress indicators, CAT and lipid peroxidation (LPO), in the midges were determined following previously developed methods (Chen et al, 2015;Qi et al, 2015). In brief, protein contents were quantified by a Bradford method using bovine serum albumin as a standard (Bradford, 1976).…”

“…On the contrary, alteration of toxicokinetics may also cause antagonism. Antagonistic interaction between permethrin and cadmium as well as cypermethrin and lead in C. dilutus was attributed to enhanced biotransformation of pyrethroids with the addition of metals (Chen et al, 2015;Mehler et al, 2011). Joint toxicity between chemicals may depend on their exposure levels (Banks et al, 2003).…”