Decreased glutathione S-transferase expression and activity and altered sex steroids in Lake Apopka brown bullheads (Ameriurus nebulosus)

A number of freshwater lakes and reclaimed agricultural sites in Central Fl orida have been the receiving waters for agrochemical and municipal runoff. One of these sites, Lake Apopka, is also a eutrophic system that has been the focus of several case studies reporting altered reproductive activity l inked to bioaccumulation of persistent organochlorine chemicals in aquatic species, The present study was initiated to determine if brown bullheads (A meriurus nebulosus) from the north marsh of Lake Apopka (Lake Apopka Marsh) exhibit an altered capacity to detoxify environmental chemicals through he patic glutathione S-transferase (GST)-mediated conjugation as compared with bullheads from a nearby reference site (Lake Woodruff). We also compared p lasma sex hormone concentrations (testosterone, 17-beta estradiol, and 11 k eto-testosterone) in bullheads from the two sites. Female bullheads from La ke Apopka had 40% lower initial rate GST conjugative activity toward 1-chlo ro-2,4-dinitrobenzene (CDNB), 50% lower activity towards p-nitrobutyl chlor ide (NBC), 33% lower activity toward ethacrynic acid (ECA), and 43% lower a ctivity toward Delta5-androstene-3,17-dione (Delta (5)-ADI), as compared wi th female bullheads from Lake Woodruff. Enzyme kinetic analyses demonstrate d that female bullheads from Lake Apopka had lower GST-catalyzed CDNB clear ance than did female Lake Woodruff bullheads. Western blotting studies of b ullhead liver cytosolic proteins demonstrated that the reduced GST catalyti c activities in female Lake Apopka bullheads were accompanied by lower expr ession of hepatic GST protein. No site differences were observed with respe ct to GST activities or GST protein expression in male bullheads. Female La ke Apopka bullheads also had elevated concentrations of plasma androgens (t estosterone and 11-ketotestosterone) as compared with females from Lake Woo druff. In contrast.. male Lake Apopka bullheads had elevated levels of plas ma estrogen but similar levels of androgens as compared with male bullheads from Lake Woodruff. Collectively, our studies indicate the presence of red uced GST protein expression, reduced GST conjugative capacity and altered s ex steroid homeostasis in female bullheads from a contaminated field site i n Central Florida. The implications of these physiological alterations in t erms of pollutant biotransformation and reproduction are discussed. (C) 200 1 Elsevier Science B.V. All rights reserved.