Mutation Research, 207 (1988) 135-139 135 Elsevier MTR 04575 Effect of copper coordination complexes on sister-chromatid exchanges in plant cells M.J. Hazen, A. Juarranz, J.C. Stockert, A. Gonzalez and D. Beltrfin-Porter Departamento de Biologla, Facultad de Ciencias, Universidad A utbnoma de Madrid, Madrid, and Departamento de Qulmica Inorgtinica, Facultad de Quimica, Universidad de Valencia, Valencia (Spain) (Received 15 July 1987) (Revision received 22 September 1987) (Accepted 14 October 1987) Keywords: Copper coordination complexes; Plant cells, SCE; Sister-chromatid exchanges, plants. Summaff The effectiveness of several copper coordination complexes in the induction of sister-chromatid exchanges (SCE) in meristematic cells of Allium cepa roots was studied. A significant increase in the frequencies of SCE was observed when cells were exposed to different concentrations of copper complexes for 3 h. This effect, which is concentration dependent, seems to be related to the possibility of intercalative binding modes between the planar copper complexes and DNA. The phenomenon of sister-chromatid exchanges (SCE) has constituted the subject of many reports during the last years (for review see Kato, 1977; Wolff, 1977; Latt, 1979; Latt et al., 1981). Al- though SCE are commonly used as a short-term mutagen-carcinogen test, their biological rele- vance and mechanism of formation are still not well understood (see Painter, 1980). Various chem- ical and physical agents have been found to cause damage to chromosomal DNA, which can be cyto- logically detected by an increase in the frequency of SCE (Latt et al., 1979, 1981). Likewise, com- pounds which bind to DNA by intercalation are potent SCE inducers (Latt and Loveday, 1978; Raj and Heddle, 1980; Cortes and Hazen, 1984; Armas-Portela et al., 1985; Villanueva et al., 1986). A complex between the chelating agent 1,10- Correspondence: Prof. Dr. Juan C. Stockert, Departamento de Biologla, Facultad de Ciencias, C-XV, Universidad Aut6noma de Madrid, Cantoblanco, Madrid-28049 (Spain). phenanthroline (OP) and copper(II) is able to induce in vitro the breakage of DNA strands in the presence of a reducing agent and 02 or H202 (Que et al., 1980; Graham et al., 1980; Marshall et al., 1981; Pope et al., 1982). This process is in- hibited by intercalating dyes and catalase and it does not occur when highly stabilized Cu(I) or Cu(II) complexes are used (Que et al., 1980; Marshall et al., 1981). Although the mechanism of DNA breakage has not yet been fully determined, it is assumed that the Cu(I)-OP complex inter- calates into DNA (Marshall et al., 1981; Uesugi et al., 1982), and that subsequent oxidation by H202 originates the scission of DNA due to the forma- tion of a highly reactive hydroxyl radical at the binding site (Goldstein and Czapski, 1986). Cu-OP is capable of recognizing and cleaving DNA from nucleosomes and chromatin (Elgin et al., 1983), showing interesting applications as a quasi-en- zymatic agent (Drew and Travers, 1984; Chen and Sigman, 1986). 0165-7992/88/$03.50 © 1988 Elsevier Science Publishers B.V. (Biomedical Division)