Inhibition of renal arachidonic acid ω-hydroxylase activity with ABT reduces blood pressure in the SHR

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Abstract
The mechanism-based cytochrome P-450 (CYP) inhibitor 1-aminobenzotriazole (ABT) was characterized as an inhibitor of renal arachidonic acid metabolism and administered to spontaneously hypertensive rats (SHRs) to determine the effect of reduced eicosanoid production on mean arterial pressure (MAP). A single intraperitoneal dose of ABT to Sprague-Dawley rats caused a dose-dependent loss of renal CYP content, arachidonic acid metabolism, and CYP4A protein. In the cortex and outer medulla, ABT showed a high degree of selectivity for the CYP4A enzymes, reflected by the potent inhibition of 19- and 20-hydroxyeicosatetraenoic acid (19- and 20-HETE) formation. A 50 mg/kg dose of ABT reduced cortical 20-HETE formation to 16.1 ± 0.82% of control and outer medullary 20-HETE formation to 23.8 ± 0.45% of control. In contrast, there was no inhibition of renal epoxygenase activity at this dose. Renal CYP content, arachidonic acid ω- and (ω-1)-hydroxylase activity, and CYP4A protein levels gradually return to control levels by 72 h after a single dose of ABT. Cortical 20-HETE formation recovered from 17.9 ± 3.15% of control at 6 h to 84.8 ± 4.67% of control at 72 h after ABT administration. A single injection of ABT to 7-wk-old SHRs caused an acute reduction in MAP, which remained suppressed for at least 12 h. The effect was maximal within 4 h and averaged 17–23 mmHg during the 4- to 12-h period after administration. 20-HETE formation was inhibited 85% in the cortex and 70–80% in the outer medulla during the period when MAP was reduced. A structurally related ABT analog 1-hydroxybenzotriazole had no effect on blood pressure or renal arachidonic acid metabolism. These results identify ABT as a selective inhibitor of renal CYP4A activity and provide further support for a role for 20-HETE in the regulation of blood pressure.