Effects of parathion on acetylcholinesterase, butyrylcholinesterase, and carboxylesterase in three-spined stickleback (Gasterosteus aculeatus) following short-term exposure

The sensitivity of butyrylcholinesterase (BChE) toward the inhibition by th e organophosphorus insecticide (OP) parathion-ethyl was compared with that of other esterases in the fish three-spined stickleback. Earlier field and in vitro results had suggested the higher sensitivity to OPs of stickleback BChE when compared with acetylcholinesterase (AChE). In the present study, stickleback were exposed in vivo under environmentally realistic condition s using a short duration of exposure (1 h) and parathion concentrations of 0.01, 0.1, and 1.0 mug/L. Seventy and 80% of nominal concentrations, respec tively, were measured in the 0.01 and 0.1 mug/L treatments. Following expos ure, stickleback were maintained in clean water for 48 h (recovery), allowi ng the metabolic activation of parathion. After recovery, the activities of BChE (axial muscle, gills, liver), AChE (brain, axial muscle, gills), and carboxyleaterase (CaE, liver) were determined. Following exposure to 1 mug/ L parathion, the BChE activity was significantly decreased in liver (simila r to 60%) and axial muscle (similar to 30%), while its decrease in gills (s imilar to 30%) was not significant. No effects on BChE activity were observ ed with 0.1 and 0.01 mug/L parathion. The AChE and CaE activities remained unaffected with all parathion concentrations used. The results are discusse d with respect to the potential application of stickleback BChE as a biomar ker of OP exposure.