Different mechanisms of acute versus long-term antihypertensive effects ofsoluble epoxide hydrolase inhibition: Studies in Cyp1a1-Ren-2 transgenicrats

Recent studies have shown that the long-term antihyper-tensive action of soluble epoxide hydrolase inhibition (sEH)in angiotensin-II (AngII)-dependent hypertension might bemediated by the suppression of intrarenal AngII levels. Totest this hypothesis, we examined the effects of acute(2 days) and chronic (14 days) sEH inhibition on bloodpressure (BP) in transgenic rats with inducible AngII-dependent hypertension. AngII-dependent malignant hyper-tension was induced by 10 days’ dietary administration ofindole-3-carbinol (I3C), a natural xenobiotic that activatesthe mouse renin gene in Cyp1a1-Ren-2 transgenic rats. BPwas monitored by radiotelemetry. Acute and chronic sEHinhibition was achieved using cis-4-(4-(3-adamantan-1-yl-ure-ido)cyclohexyloxy) benzoic acid, given at doses of 0.3, 3, 13,26, 60 and 130 mg/L in drinking water. At the end ofexperiments, renal concentrations of epoxyeicosatrienoicacids, their inactive metabolites dihydroxyeicosatrienoicacids and AngII were measured. Acute BP-lowering effectsof sEH inhibition in I3C-induced rats was associated with amarked increase in renal epoxyeicosatrienoic acids to di-hydroxyeicosatrienoic acids ratio and acute natriuresis.Chronic treatment with cis -4-(4-(3-adamantan-1-yl-ureido)cy-clohexyloxy) benzoic acid in I3C-induced rats eliciteddose-dependent persistent BP lowering associated with asignificant reduction of plasma and kidney AngIIlevels. Our findings show that the acute BP-lowering effectof sEH inhibition in I3C-induced Cyp1a1-Ren-2 transgenicrats is mediated by a substantial increase in intrarenal ep-oxyeicosatrienoic acids and their natriuretic action withoutaltering intrarenal renin–angiotensin system activity. Long-term antihypertensive action of cis-4-(4-(3-adamantan-1-yl-ureido)cyclohexyloxy) benzoic acid in I3C-induced Cyp1a1-Ren-2 transgenic rats is mediated mostly by suppression ofintrarenal AngII concentration.