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Effect of naphthalene on the hemolymph ion concentrations of Chironomus attenuatus and the possible mode of action
Author(s) -
Harmon H. James,
Sanborn Mark R.,
Darville Roy G.,
Wilhm Jerry L.
Publication year - 1983
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620020407
Subject(s) - chemistry , phenanthrene , naphthalene , atpase , membrane , hemolymph , biochemistry , biophysics , mode of action , toxicity , ouabain , environmental chemistry , enzyme , sodium , biology , organic chemistry
Naphthalene, a polycyclic aromatic hydrocarbon (PAH), was examined for its effect on the ionic regulation of the freshwater dipteran Chironomus attenuatus. Exposure of the fourth instar larvae to 1 mg/L naphthalene for 1 h resulted in elevated hemolymph Na+, K+ and Cl − concentrations. After documenting the loss of ionic regulation in Chironomus exposed to naphthalene, we designed several experiments to elucidate the mode of action of naphthalene and other PAH (naphthol, phenanthrene, chrysene) on ionic regulation. Lipid vesicles were used to simulate biological membranes to test if PAH cause a loss of structural membrane integrity. Cellular membrane transport is mediated by the Na+, K+‐ATPase enzyme system. Inhibition of this system was tested using cultured mammalian cells (HEp‐2), which have a ouabain‐sensitive Na+, K+‐ATPase. Ion leakage experiments using Na+, K+ and cytochrome c ‐loaded liposomes resulted in little ionic leakage, suggesting that PAH do not cause a loss of membrane integrity. Exposure of plasma membranes of cultured cells to PAH (10 mg/L) for 30 min caused inhibition of ouabain‐sensitive Na+, K+‐ATPase. Data indicated that as the molecular size of the PAH increased, the inhibition decreased. Thus, our data support the hypothesis that loss of ionic regulation in aquatic organisms is due to inhibition of specific enzyme systems and not to a general alteration of membrane integrity.