The present study tested the hypothesis that cytochrome P-450 (CYP) metabolites of arachidonic acid (AA) are involved in mediating hypertension and renal vasoconstriction during chronic reductions in uterine perfusion pressure (RUPP) in pregnant rats. 1-aminobenzotriazole (ABT), a CYP enzyme inhibitor (25 mg/kg per day), or vehicle (saline 0.9%) was administered for 7 days to normal pregnant (NP) rats and to pregnant rats with chronic RUPP. RUPP rats infused with vehicle showed significantly (P<0.01) higher mean arterial pressure (MAP) (130+/-2 versus 106+/-1 mm Hg), renal vascular resistance (RVR) (22.6+/-1.8 versus 16.3+/-1.1 mm Hg/mL per minute) and lower (P<0.05) glomerular filtration rate (GFR) (1.6+/-0.1 versus 2.3+/-0.1 mL/min) than NP rats. ABT decreased (P<0.01) MAP in RUPP rats (111+/-1 mm Hg), whereas it had no effect in NP rats (108+/-2 mm Hg). CYP inhibition also attenuated the differences in renal hemodynamics observed between NP and RUPP rats. After treatment with ABT, RVR and GFR were similar in RUPP rats (19.3+/-1.5 mm Hg/mL per minute and 2.0+/-0.2 mL/min, respectively) and NP rats (16.3+/-2.4 mm Hg/mL per minute and 2.4+/-0.2 mL/min). The effects of CYP enzymes inhibitor in RUPP rats were associated with a reduction (P<0.05) of 20-HETE formation (32%) and a decreased (P<0.05) expression (33%) of CYP4A protein in renal cortex. In contrast, renal epoxygenase activity did not change in these animals. These results suggest that 20-HETE contributes to hypertension and renal vasoconstriction induced by chronic RUPP in pregnant rats.