Effects of salt, prostaglandin, and captopril on vascular responsiveness in essential hypertension

To examine the influence of dietary sodium, prostaglandin, and captopril on vascular reactivity, 12 patients with essential hypertension (EH) and seven normotensive subjects (NT) were given a high sodium diet and thereafter a low sodium diet, each for ten days. Indomethacin (IND) (150 mg/d) was administered during the last three days of each dietary period. Blood pressure and cardiac output (CO) (by impedance cardiography) were measured during the angiotensin II (Ang II) infusion before and after the IND treatment of each dietary period. In eight patients with EH, captopril 100 mg was given before Ang II infusion. EH patients were classified as either salt sensitive (SS) or nonsalt sensitive (NSS). The mean blood pressure (MBP) response to Ang II was significantly higher on high sodium intake than on low sodium intake in NSS and NT, but not in SS. IND significantly increased the MBP response to Ang II on low sodium intake in NSS and NT, but not in SS. IND significantly increased the TPR response to Ang II on low sodium intake, remarkably in NSS and NT compared with SS. Salt sensitivity (% decrease in MBP from high to low sodium intake) highly correlated with the increase in the TPR response to Ang II by IND on low sodium intake (r = -0.90). After captopril administration, IND still increased the MBP and TPR response to Ang II on low sodium intake. These results suggest that the modulation of the vascular responsiveness to Ang II by prostaglandins is altered by sodium balance and salt sensitivity in EH.