Salt-sensitive hypertension after exposure to angiotensin is associated with inability to upregulate renal epoxygenases.

The current study was designed to determine whether angiotensin II infusion could lead to persistent salt-sensitive hypertension and to examine involvement of renal microvascular epoxygenases in this process. Six groups were studied: rats maintained on a normal salt diet for 4 weeks (NS); rats maintained on a high salt diet for 4 weeks (HS); and all other animals receiving angiotensin II (ANG) infusion and being fed a normal or high salt diet for 2 weeks; then the angiotensin II infusion was stopped and diets were either maintained or switched (ANG/NS-NS, ANG/NS-HS, ANG/HS-HS, ANG/HS-NS). Angiotensin II infusion resulted in a rise in blood pressure and an increase in urinary albumin excretion over the 2-week period. After angiotensin II withdrawal, blood pressure returned to normal in animals receiving a normal salt diet from weeks 2 to 4 (ANG/NS-NS and ANG/HS-NS groups). In contrast, blood pressure remained elevated in the group maintained on a high salt diet throughout the entire 4-week period (ANG/HS-HS group). Renal microvascular CYP2C11 and CYP2C23 protein levels were decreased by 50% to 60% in the ANG/HS-HS group compared with the NS group. Likewise, renal microvascular CYP2J protein was significantly decreased in the ANG/HS-HS group versus the NS group. Renal microvascular CYP2C11 and CYP2C23 mRNA levels were reduced in the ANG/HS-HS group compared with both the NS and HS groups. These results support the hypothesis that angiotensin II infusion induces persistent salt-sensitive hypertension after withdrawal of angiotensin II that may be due to downregulation of CYP2C and CYP2J epoxygenases in renal microvessels.