Altered glutathione S-transferase catalytic activities in female brown bullheads from a contaminated central Florida lake

Brown bullheads (Ameriurus nebulosus) are a demersal freshwater species tha t can be found in a number of polluted ecosystems. The purpose of the prese nt study was to determine the overall capacity for in vitro glutathione S-t ransferase (GST) detoxification by brown bullheads, and to see if bullhead GST catalysis was altered in bullheads from a polluted site. Brown bullhead liver cytosolic GSTs catalyzed the conjugation of 1-chloro-2,4-dinitrobenz ene (CDNB) over a large range of substrate concentrations, with apparent K- m and V-max for CDNB at fixed nucleophile (glutathione, GSH) concentrations of 1.8-1.9 mM and 12.1-14.6 mu mol CDNB conjugated/min/mg, respectively. B ullhead GSTs were also highly active toward other substrates such as ethacr ynic acid (ECA), Delta5-androstene-3,17-dione (ADI), and nitrobutyl chlorid e (NBC). Initial rate GST catalytic activities toward CDNB, NBC, EGA, and A DI were significantly lower in female bullheads from a contaminated lake (L ake Apopka Marsh) as compared to female bullheads inhabiting a nearby contr ol site (Lake Woodruff). No site differences were observed with respect to male bullhead GST activities. These studies suggest that brown bullheads ef ficiently carry out GST conjugation of diverse electrophilic substrates. Ho wever, bullhead GST catalysis may be compromised in bullheads inhabiting po lluted ecosystems. (C) 2000 Elsevier Science Ltd. All rights reserved.