MATERNAL SALT INTAKE AND MICROVASCULAR ENDOTHELIAL FUNCTION DURING THE THIRD TRIMESTER OF HEALTHY PREGNANCY

Abstract

Objective: Even in healthy individuals, high-salt (HS) loading leads to endothelial dysfunction, a hallmark of cardiometabolic diseases, independently of the changes in blood pressure (BP). Still, the effect of the amount of daily salt intake during healthy pregnancy on maternal endothelium-dependent vascular reactivity has not yet been investigated. Thus, this study aimed to assess the effect of the amount of daily salt intake during third trimester of pregnancy on maternal microvascular reactivity to stimuli in healthy pregnant women. Design and method: The present study was designed as a cross-sectional study in which all the data for each pregnant woman were obtained at one-time point between 37 and 40 weeks of gestation. Daily salt intake was estimated based on 24-h urinary sodium excretion using appropriate formula [1-g salt (NaCl) = 393.4 mg Na = 17.1 mmol Na]. Microvascular endothelium-dependent vasodilation in response to vascular occlusion (PORH), iontophoresis of acetylcholine (AChID) and local heating (HEAT), as well as endothelium-independent vasodilation in response to iontophoresis of sodium nitroprusside (SNP) was assessed by Laser Doppler flowmetry (LDF). Results: Preliminary results of the present study involve data obtained from 27 healthy pregnant women. According to the amount of daily salt intake, pregnant women were divided in low-salt (LS, < 5 g of salt/day, N = 4), normal-to-high salt (NHS, 5.0–7.5 g of salt/day, N = 12) and high-salt (HS, > 7.5 g of salt/day, N = 11) group. All pregnant women were normotensive, and BP values did not differ between groups. HEAT was significantly lower in HS compared to LS and NHS group, while PORH and AChID tended to be lower in HS compared to LS and NHS group, but without statistical significance. SNPID did not significantly differ between the groups. There was weak to moderate negative correlation between daily salt intake and functional markers of microvascular endothelium-dependent vasodilation (PORH, AChID and HEAT). Conclusions: The amount of daily salt intake significantly affects maternal endothelium-dependent microvascular reactivity during third trimester of healthy pregnancy, i.e. the increased salt intake significantly reduces the endothelium-dependent dilatation of the skin microcirculation, especially responses mediated by nitric-oxide (NO).