Abstract-High-salt (HS) diet is often associated with increased vascular resistance and arterial pressure; however, the effects of HS intake on the vascular control mechanisms of arterial pressure during pregnancy are unclear. We investigated whether a HS diet during pregnancy is associated with increases in vascular reactivity. Active stress was measured in aortic strips of virgin and normal pregnant Sprague-Dawley rats and a hypertensive pregnant rat model produced by reduction in uterine perfusion pressure (RUPP), fed either normal-sodium (NS, 1%) or HS diet (8%) for 7 days. In endothelium-intact strips, phenylephrine (Phe) caused a concentration-dependent contraction that was greater in RUPP rats than in normal pregnant or virgin rats and was significantly enhanced in pregnant/HS and RUPP/HS rats compared with pregnant/NS and RUPP/NS rats, respectively. Removal of the endothelium enhanced the Phe-induced stress slightly in virgin rats and significantly in pregnant/NS but not in pregnant/HS, RUPP/NS, or RUPP/HS. In endothelium-intact strips, acetylcholine (ACh) caused a concentration-dependent relaxation that was reduced in RUPP/NS (max, 31%) compared with pregnant/NS rats (max, 75%). ACh relaxation was further reduced in pregnant/HS rats compared with pregnant/NS rats and in RUPP/HS rats compared with RUPP/NS rats. Pretreatment of endothelium-intact strips with N G -nitro-L-arginine methyl ester (L-NAME, 10 Ϫ4 mol/L), to inhibit NO synthase, or withϪ6 mol/L), to inhibit cGMP production in smooth muscle, inhibited ACh-induced relaxation and enhanced Phe-induced contraction in pregnant/NS rats but not in pregnant/HS, RUPP/NS, or RUPP/HS rats. Basal and ACh-induced nitrite/nitrate production from aortic strips showed significant reduction in pregnant/HS rats compared with pregnant/NS rats but not in RUPP/HS rats compared with RUPP/NS rats. Sodium nitroprusside, an exogenous NO donor, caused relaxation of Phe contraction that was similar in virgin or pregnant rats on an NS or HS diet but was significantly reduced in RUPP/HS rats (ED 50 6ϫ10Ϫ8 mol/L) compared with RUPP/NS rats (ED 50 6ϫ10 Ϫ9 mol/L). Thus, a HS diet in normal pregnant and RUPP rats is associated with increases in vascular reactivity. The enhanced vascular reactivity with the HS diet is possibly related to abnormalities in NO synthesis/release from the endothelium in normal pregnant rats and an additional decrease in the sensitivity of the smooth muscle to relaxation by NO in pregnant rats with reduced uterine perfusion pressure. Key Words: arterial pressure Ⅲ endothelium Ⅲ nitric oxide Ⅲ muscle, smooth, vascular Ⅲ contraction H igh-salt (HS) diet has been implicated in the pathogenesis of hypertension, particularly in salt-sensitive individuals, and salt moderation is often recommended to protect against excessive increases in vascular resistance and arterial pressure. 1,2 However, the interrelationship between sodium intake, vascular resistance, and blood pressure regulation during pregnancy is less clear. During normal pregnancy, reductions in s...

Abstract-Hypertension is more common in men and postmenopausal women than in premenopausal women, and gender differences in sensitivity to high dietary Na ϩ salt have been suggested; however, the vascular mechanisms involved are unclear. We investigated whether increases in the extracellular concentration of Na