OBJECTIVE: This investigation examined the physiological and biochemical changes in pregnant rats following treatment with the nitric oxide synthase inhibitor, L nitroarginine methyl ester (L-NAME). METHODS: Pregnant and non-pregnant animals were administered L-NAME, and blood pressure and proteinuria were monitored. On day 21 of pregnancy, the animals were euthanized, and fetal and placental weight and number were recorded. Placental tissues were homogenized and assayed for lipid peroxides, protein carbonyls, superoxide dismutase, glutathione peroxidase, and thioredoxin reductase. RESULTS: Significant increases in blood pressure, urinary protein concentrations, and reduced pup weights were observed in pregnant rats treated with L-NAME. There was no significant increase in lipid or protein oxidation after treatment with L-NAME, and no difference was found in the activities of superoxide dismutase, glutathione peroxidase, and thioredoxin reductase. DISCUSSION: The L-nitroarginine methyl ester model of experimental preeclampsia induces a number of the physiological characteristics typical of the human disease however fails to initiate biochemical changes in the placenta that occur during human preeclampsia.