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METALATHIONEIN AND GLUTATHIONE IN AN ACUTE RESPONSE TO COPPER IN MERCENARIA MERCENARIA BROWN CELLS IN VIVO
Citation:
Zaroogian, G, E Jackim, AND C Norwood. METALATHIONEIN AND GLUTATHIONE IN AN ACUTE RESPONSE TO COPPER IN MERCENARIA MERCENARIA BROWN CELLS IN VIVO. Presented at Society of Environmental Toxicology and Chemistry, Baltimore, MD, November 11-15, 2001.
Description:
Brown cells are found in the red glands of Mercenaria mercenaria (Bivalvia) and have been shown to accumulate, detoxify and excrete metals. Brown cell involvement in metal detoxification is due in part to endogenous glutathione (GSH) and metallothionein (MT). GSH and MT have been shown to play an important role in metal detoxification in bivalve molluscs. The intent of this study is to show that brown cell GSH functions in acute protection against CU 2+ toxicity, that GSH provides the initial defense against Cu2+ toxicity prior to MT induction and MT variants (MT-I and MT-II) are unequal in response to Cu2+. During treatment of Mercenaria with 0.01 and 0.05 ppm Cu2+, brown cells were analyzed for MT by capillary electrophoresis and GSH colorimetrically at 0, 0.25, 1, 2, 3 and 4 days. A significant (R2=0.99, P< 0.05) linear increase in GSH with the 0.01 ppm Cu2+ treatment was observed to day 1, after which a decrease in concentration occurs with no apparent change in concentration to day 4. The maximum concentration of GSH in the 0.05 ppm Cu2+ treatment also appears at day 1. However, a significant (R2= 0.91, P< 0.05) linear decrease was observed from day 1 to day 4. A significant (R2= 0.94, P< 0.01) linear increase occurs in MT from day 0 to day 4 in the 0.01 ppm Cu2+ treatment, with a maximum concentration occurring at day 4. With the 0.05 ppm Cu2+ treatment, a maximum MT concentration occurs at day 2 with a significant (R2= 0.99, P< 0.01) linear decrease from day 2 to day 4, which is probably due to toxicity. The change in ratio of MT-I/MT-II during the 4 days of treatment to Cu2+ is due to a greater relative change in MT -I than in MT-II. The variants of brown cell MT appear to respond differentially to Cu2+ depending upon intracellular Cu2+ concentration. It appears that brown cell GSH protects against acute Cu 2+ toxicity and provides an initial defense against Cu2+.