Salt-sensitive hypertension in conscious rats induced by chronic nitric oxide blockade

This study examined the effects of alterations in salt-intake on blood pressure (BP) in rats chronically treated intravenously with or without the nitric oxide synthase (NOS) inhibitor N G-nitro- l-arginine methyl ester (L-NAME) (8.6 mg/kg/day). The changes in mean arterial pressure (MAP), the renal cortical and medullary blood flow (CBF and MBF), and the sodium balance were determined by implanted optical fibers and laser-Doppler flow measurement techniques in the conscious rats. The results showed that high salt intake (7.4 mEq/day) elevates CBF (139% ± 15%), but has no significant effect on MAP or MBF in control rats; in L-NAME-treated rats, high salt intake elevates MAP, produces no change in CBF, and decreases MBF (51% ± 14%), as well as increasing the sodium balance (0.26 ± 0.23 mEq/day to 1.29 ± 0.47 mEq/day). The present experiments indicated that NO appears to maintain the MBF during high salt intake and to prevent the changes in MAP, and, in the absence of NO, salt-sensitive hypertension develops. Nitric oxide plays an important role in the development of salt-sensitive hypertension with the change of MBF.