REID, Inefta*; CARROLL, Margaret A.; FLORES, Liz; CATAPANE, Edward J.; Medgar Evers College; Medgar Evers College; Kingsborough Community College; Medgar Evers College: A Comparative Study of the In Vivo and In Vitro Effects of Copper on Glutathione S-Transferase Activity in Gill Tissue of the American Oyster,

Copper is a common aquatic pollutant. While bivalve mollusks are used for monitoring and bioaccumulation kinetics studies, little is known about their biochemical responses to metal accumulation. Metal accumulation can increase oxidative stress by various means including depletion of cellular antioxidants like glutathione (GSH). Glutathione S-Transferase (GTS) is a ubiquitous group of Phase II detoxification enzymes that catalyze the conjugation of electrophilic substrates to GSH. This study showed Cu⁺² had an in vitro and in vivo inhibitory effect on Crassostrea virginica gill GST activity which could be offset by additional GSH. Gill was removed and processed to obtain the post-mitochondrial supernatant. GST activity was measured spectrophotometrically using CDNB and GSH as substrates. The presence of 65, 130, 270, or 400 µM Cu⁺² in the assay resulted in a 15, 30, 85, or 95% loss of GST activity, respectively and the presence of additional GSH significantly prevented this inhibitory effect. In other experiments, gills were removed and divided into 5 pieces. Each piece was preincubated 5 hours in ASW under various concentrations of Cu⁺² then GST activity determined. Preincubation with 200, 400, 600, or 800 µM Cu⁺² resulted in a 20, 33, 40, or 60% loss of GST activity, respectively. This inhibition could be reversed by the adding GSH to the preincubation media. This study will help gain further insight into the role of toxic metal exposures on oxidative stress and the cellular mechanisms defending against it. This work was supported by grants 1R25GM62003 of NIGMS, 0516041071 of NYSDOE, 66288-0035 of PSC-CUNY, and LSAMP-CUNY. We thank Frank M. Flower & Sons, Inc., Oyster Bay, NY for supplying oysters.