['To assess whether the extent of LDL oxidation influences its cytotoxic effects, thus contributing to its atherogenic potential.', 'The effects of native and modified LDL on cultured human coronary artery smooth muscle cells (SMC) and endothelial cells (ECs) were investigated.', "Four indices of cytotoxicity were studied: (i) chromium-51 release; (ii) 5-bromo-2'-deoxyuridine (BrDUrd) uptake; (iii) morphological appearance; and (iv) EC migration.", '(i) Minimally modified (mm) LDL (400 micrograms/ml) causes significant 51Cr release; the cytotoxic effect was significantly greater for copper oxidised (ox) LDL (400 micrograms/ml). Native LDL had no effect. (ii) BrDUrd uptake studies showed significant inhibition of cell proliferation by 100 micrograms/ml of oxLDL and to a lesser extent by mmLDL; native LDL had no effect. (iii) Morphological appearance was not altered by native LDL. Changes in cell morphology were induced by mmLDL (400 micrograms/ml), and were more pronounced with oxLDL in concentrations of > or = 200 micrograms/ml. (iv) EC migration was significantly inhibited by oxLDL (100 micrograms/ml), but not by native or mmLDL.'] Does extent of oxidative modification of low density lipoprotein determine the degree of cytotoxicity to human coronary artery cells?