['Substrates of Fenton reaction (Fe(2+)+H(2)O(2)-->Fe(3+)+*OH+OH-) may be used to experimentally induce oxidative damage to macromolecules. The study aimed at evaluating effects of Fe(2+) and/or H(2)O(2) on lipid peroxidation in porcine ovary homogenates.', 'Ovary homogenates were incubated in the presence of either H2O2 (100, 50, 25, 10, 5.0, 2.5, 1.0, 0.5, 0.25, 0.01, 0.001 mM) or FeSO(4) (Fe2+) (300, 150, 75, 30, 15, 7.5, 3.0, 1.5, 0.75 microM), or of those two factors used together: Fe(2+) (30 microM) plus H(2)O(2) (concentrations as above), or H(2)O(2) (0.5 mM) plus Fe(2+) (concentrations as above). The concentration of malondialdehyde+4-hydroxyalkenals constituted the lipid peroxidation index.', 'H(2)O(2) alone did not affect lipid peroxidation in porcine ovary homogenates at all, whereas Fe(2+) (300, 150, 75, 30, and 15 microM) alone increased lipid peroxidation in a concentration dependent manner. When Fe(2+) and H(2)O(2) were applied together, lipid peroxidation increased significantly without any concentration related effect of H(2)O(2), but with a clear concentration dependent effect of Fe(2+); the damaging effect of Fe(2+), used together with H(2)O(2), was the same as the one, obtained after Fe(2+) was applied alone.'] Is external hydrogen peroxide indispensable for experimental induction of lipid peroxidation via Fenton reaction in porcine ovary homogenates?