Involvement of calcium and iron in Quin 2 toxicity to isolated hepatocytes.
When treated with the cytosolic Ca++ indicator Quin 2-acetoxymethyl ester (Quin 2-AM), isolated hepatocytes exhibited signs of toxicity, such as extensive lipid peroxidation and vitamin E loss and release of lactate dehydrogenase. Lipid peroxidation induced by this agent was blocked completely by cotreatment of the cells with ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, EDTA, ruthenium red, carbonyl cyanide m-chlorophenylhydrazone, desferal and trifluoperazine, and was partially inhibited by quinacrine and indomethacin. With the exception of carbonyl cyanide m-chlorophenylhydrazone and quinacrine, these agents also inhibited lactate dehydrogenase leakage. Although the results with ruthenium red suggested that Quin 2-AM may cause toxicity by altering handling of Ca++ by mitochondria, mitochondrial membrane potential was not altered in cells treated with Quin 2-AM until after toxicity occurred. Evidence of a direct, potentiative effect of Quin 2 on iron-induced lipid peroxidation was gained from experiments with liposomes. Treatment of cells with Quin 2-AM did not enhance nitro blue tetrazolium reduction, suggesting that Quin 2 did not stimulate O2- production by the cells. Direct chelation of Ca++ did not appear to be involved in the mechanism of Quin 2 toxicity, for an analog of Quin 2 that is virtually nonhydrolyzable, which greatly limits the binding of Ca++, also caused lipid peroxidation and cell death. These results suggest that Quin 2 causes toxicity by chelating iron or by activating some cellular process(es) that is dependent on the presence of iron or Ca++.
Carpenter-Deyo
L
L
Environmental Health Sciences Center, Oregon State University, Corvallis.
Reed
D J
DJ
D000634:Aminoquinolines / Q000633:toxicity*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002614:Chelating Agents / Q000633:toxicity*; D005456:Fluorescent Dyes / Q000633:toxicity*; D066298:In Vitro Techniques; D007501:Iron / Q000502:physiology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000634:Aminoquinolines; D002614:Chelating Agents; D005456:Fluorescent Dyes; C035738:Quin2-acetoxymethyl ester; D007501:Iron; D007770:L-Lactate Dehydrogenase; D002118:Calcium