In Vitro Effects of Agriculture Pollutants on Microcrustacean and Fish Acid Phosphatases

Chemical inputs from agricultural activities represent a threat to aquatic biota and its biochemical systems. Among these systems, acid phosphatases are involved in autophagic digestive processes, decomposing organic phosphates, signaling pathways, and other metabolic routes. In vitro tests are helpful to generate hypotheses about pollutant mechanisms of action through comparison of the toxicity effects of these compounds. In this work, we investigated the inhibitory effects of four organic pesticides and three metals on the acid phosphatases extracted from the freshwater microcrustacean Daphnia similis and the fish Metynnis argenteus. Our results demonstrated that only the metals have considerable inhibitory effects (50% or higher) on the enzyme activities. The calculated median effect concentrations (IC50) for the enzyme inhibition were 0.139 mM Hg2+ (fish enzyme), 0.652 mM Cu2+ (fish enzyme), and 1.974 mM Al3+ (Daphnia enzyme). Due to the relatively low value of the inhibition parameter for Hg2+, its inhibitory property could be used as a tool for Hg2+ detection in environmental samples. The enzyme activities obtained in the presence of the inhibitors are potential data as in vivo biomarkers for metals in both aquatic species.