DDT inhibition of Ca-ATPase of the peripheral nerves of the American lobster |
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Authors: | SM Ghiasuddin Fumio Matsumura |
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Institution: | Department of Entomology, University of Wisconsin, Madison, Wisconsin 53706 USA |
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Abstract: | A Ca-ATPase highly sensitive to DDT has been found in peripheral nerves of lobster, Homarus americanus. The observed I50 for this Ca-ATPase toward DDT is on the order of 10?9M and has a low temperature quotien. The ATPase seems to work over a wide range of ATP concentrations. It is stimulated by Ca2+ (optimum 0.1 mM) and shows sensitivity to Na+ (optimum 20 mM) and K+ (optimum 20 mM) ions. The fact that it is highly sensitive to ruthenium red (I50 = 10 μM) suggests that the enzyme is a Ca-ATPase and not a Mg-ATPase. Furthermore the enzyme is not a CaMg-ATPase, since the presence of Mg2+ along with Ca2+ ion is not required for its activity. DDT is found to inhibit the process of Ca2+ binding in the axonic membrane only in the presence of ATP. The evidence suggests the important role of the Ca-ATPase in regulating Ca2+ concentrations in the membrane. The possible significance of DDT inhibition of the ATPase is discussed. |
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