Nacl Loading Impairs Endothelium-Dependent Vasodilation in Renal Artery, But not in Brachial Artery, in Salt-Sensitive Patients with Essential Hypertension
The purpose of this study is to determine whether there was a difference in endothelial function response to NaCl loading between vascular beds in essential hypertensive patients. We evaluated the effects of the intravenous administration of L- and D-arginine (500 mg/kg over 30 min.) on renal hemodynamics in 22 patients with essential hypertension (13 salt-resistant (SR) and 9 salt-sensitive (SS)) and the effects of intraarterial infusion of acetylcholine and isosorbide dinitrate (ISDN) on forearm hemodynamics in 18 patients (10 SR and 8 SS) on each salt diet period (low-salt; NaCl 50 mmol/day, high-salt; NaCl 340 mmol/day, for 1 week, respectively). L-arginine-induced renovascular relaxation was less in SS than in SR during a high salt diet (renal blood flow: 5.6±1.9 vs. 12.4±2.8%; renal vascular resistance: -7.0±2.1 vs. -13.4±2.5%, p<0.05, respectively), but not during a low salt diet. The increase in urine nitraite/nitrate (NOx) excretion evoked by L-arginine was also less in SS than SR during a high salt diet (86±18 % vs. 126±23 %, p<0.05). D-arginine infusion did not change the urine NOx excretion. The forearm blood flow responses to acetylcholine and ISDN were similar in SS and SR during the both salt diets. These findings suggest that renal, but not forearm, endothelial function may be modified by salt loading in SS and this modification may participate in the salt-sensitivity in patients with essential hypertension.