Does Roundup affect zinc functions in a bivalve mollusk in ex vivo exposure?
Abstract Roundup (Rn), a glyphosate-based formulation, is one of the most frequently used herbicides in the world. It was found to affect non-targeted organisms in several ways including adhesive activity towards metal ions. Zinc (Zn) plays a crucial role in a number of biochemical processes. The aim of this study was to elucidate the direct impact of Rn on the Zn accumulation and Zn- dependent activities in the ex vivo system. Samples of the digestive gland of a bivalve mollusk Unio tumidus were exposed to 3 µM of Rn, Zn, Zn chelator N,N,N′,N′-Tetrakis(2- pyridylmethyl)ethylenediamine) (TPEN, Tp) and their combinations ZnTp and ZnRn for 17 h. The levels of Zn in the tissue (Zn t) and metallothioneins (Zn-MT), metallothioneins (MTSH) and glutathione (GSH & GSSG), total antioxidant capacity (TAC), lysosomal membrane integrity and caspase-3 activity were determined. Here we demonstrate that the Rn and Tp have different effects on the Zn accumulation and functionality. Rn did not affect the accumulation of Zn (Zn t, Zn-MT) in the Zn- and ZnRn-groups. In contrary, Tp produced effects antagonistic to Zn on caspase-3 activity, lysosomal stability and MTSH concentration. Rn caused particular pro-oxidative effect decreasing GSH level (Rn- and ZnRn-groups) and lysosomal stability (Rn- group). The shared affected index was the GSH/GSSG ratio, which decreased by 2-8 times in each exposure. This is the first experience with the Tp application to indicate Zn activity in mollusks. To summarize, the ex vivo approach can be useful in the study of numeral aquatic pollutants.