High sodium intake during postnatal phases induces an increase in arterial blood pressure in adult rats

Abstract

Epigenetic studies suggest that diseases that develop in adulthood are related to certain conditions to which the individual is exposed during the initial stages of life. Experimental evidence has demonstrated that offspring born to mothers maintained on high-Na diets during pregnancy have higher mean arterial pressure (MAP) in adulthood. Although these studies have demonstrated the importance of prenatal phases to hypertension development, no evidence regarding the role of high Na intake during postnatal phases in the development of this pathology has been reported. Therefore, in the present study, the effects of Na overload during childhood on induced water and Na intakes and on cardiovascular parameters in adulthood were evaluated. Experiments were carried out in two groups of 21-d-old rats: experimental group, maintained on hypertonic saline (0·3 M-NaCl) solution and food for 60 d, and control group, maintained on tap water and food. Later, both groups were given water and food for 15 d (recovery period). After the recovery period, chronic cannulation of the right femoral artery was performed in unanaesthetised rats to record baseline MAP and heart rate (HR). The experimental group was found to have increased basal MAP (98·6 (SEM 2·6) v. 118·3 (SEM 2·7) mmHg, P, 0·05) and HR (365·4 (SEM 12·2) v. 398·2 (SEM 7·5) beats per min, P, 0·05). There was a decrease in the baroreflex index in the experimental group when compared with that in the control group. A water and Na intake test was performed using furosemide. Na depletion was found to induce an increase in Na intake in both the control and experimental groups (12·1 (SEM 0·6) ml and 7·8 (SEM 1·1), respectively, P , 0·05); however, this increase was of lower magnitude in the experimental group. These results demonstrate that postnatal Na overload alters behavioural and cardiovascular regulation in adulthood.Key words: Hypertension: Water intake: Sodium intake: Postnatal periodThe maintenance of a stable internal environment is the main target of all physiological processes (1,2) , which is positively correlated with the regulation of ionic concentrations in the intracellular and extracellular compartments. Among the different types of inorganic salts present in the body fluids, NaCl is the most predominantly consumed salt and Na concentration is directly related to the maintenance of body fluid homeostasis (1,2) . Changes in Na concentrations result in an osmotic flux between the intracellular and extracellular compartments. Na influx or efflux affects the concentrations of all the other components in these compartments. Therefore, it is not surprising that many homeostatic mechanisms exist to maintain plasma Na concentrations with a limited rate of variation.The regulation of blood pressure (BP) involves complex mechanisms, including local, hormonal, neuronal and renal regulation, that, working together, are responsible for the redistribution of blood through changes in peripheral vascular resistance and cardiac output. Experimental evidence has demons...

Chronic high-sodium diet intake after weaning lead to neurogenic hypertension in adult Wistar rats

“…Therefore, the 12 weeks of HS diet may have little effect on mechanism regulating food intake in this model. It has been shown elsewhere that weaned rats drinking saline solution for water over 8 weeks 12 ate and grew less than respective controls. One may conclude that such approach may compromise overall animal nutrition and bring upon other hypertensive factors since previous studies have proposed that protein restriction can result in cardiovascular dysfunctions 12 .…”

“…It has been shown elsewhere that weaned rats drinking saline solution for water over 8 weeks 12 ate and grew less than respective controls. One may conclude that such approach may compromise overall animal nutrition and bring upon other hypertensive factors since previous studies have proposed that protein restriction can result in cardiovascular dysfunctions 12 . Here, rats were exposed to sodium overload just after weaning, which is a crucial period of growth and maturation of several different physiological systems.…”

“…High salt intake has been associated with high blood pressure (BP) since 1904, when Ambard and Beaujard first established this correlation 4 . Since then, an overwhelming number of studies have been made on this topic and linked hypertension to high-sodium intake both in humans 3 and experimental 5–12 models. Yet, some questions regarding salt-dependent hypertension remain elusive, in particular, those concerning whether the amount of daily sodium consumption in the diet by humans can, per se , elicit hypertension in rodent models.

Figure 1Sodium (Na) intake ( A ), sodium excretion ( B ) and 24-hours sodium balance ( C ) of rats from HS, HS Unload and respective control groups.

…”

“…Adult Sprague-Dawley rats under moderate salt diet (2% NaCl) and chronic infusion of angiotensin II, which clamps circulating angiotensin II levels, develop high levels of blood pressure within days after infusion starts 15, 16 . Replacement of drinking water by sodium chloride solution results in high salt/water intake relation and also lead to hypertension in adult rats 12, 17 . One issue here is that none of the mentioned conditions are common in humans under high sodium intake and displaying high blood pressure.…”

Dietary Intake of Sodium during Infancy and the Cardiovascular Consequences Later in Life: A Scoping Review

“…We found that high sodium intake in the first week of life was associated with adverse health outcomes in later life in several animal experiments [12,13,[32][33][34][35][36], whereas high sodium intake after this period was not, suggesting that the timing of taste exposure is important. In line with this, the results of Moreira et al [33] indicate that an overload of sodium intake during the postnatal period permanently alters the excretion patterns and spontaneous sodium intake patterns in adult- hood. Furthermore, sodium intake during postnatal period promotes salty food preferences in adulthood [33].…”