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

Abstract

In this study, we investigated some mechanisms involved in sodium-dependent hypertension of rats exposed to chronic salt (NaCl) intake from weaning until adult age. Weaned male Wistar rats were placed under high (0.90% w/w, HS) or regular (0.27% w/w, Cont) sodium diets for 12 weeks. Water consumption, urine output and sodium excretion were higher in HS rats compared to control. Blood pressure (BP) was directly measured by the arterial catheter and found 13.8% higher in HS vs Cont rats. Ganglionic blockade with hexamethonium caused greater fall in the BP of HS rats (33%), and central antagonism of AT1 receptors (losartan) microinjected into the lateral ventricle reduced BP level of HS, but not of Cont group. Heart rate variability analysis revealed sympathetic prevalence on modulation of the systolic interval. HS diet did not affect creatinine clearance. Kidney histological analysis revealed no significant change in renal corpuscle structure. Sodium and potassium concentrations in CSF were found higher in HS rats despite no change in plasma concentration of these ions. Taken together, data suggest that animals exposed to chronic salt intake to a level close to that reported for human’ diet since weaning lead to hypertension, which appears to rely on sodium-driven neurogenic mechanisms.

Measurement of cations, anions, and acetate in serum, urine, cerebrospinal fluid, and tissue by ion chromatography

“…Plasma Na + reported was around 143 mmol/L, plasma K + around 4.7 mmol/L, CSF Na + : 147.8 ± 4.8 mmol/L and CSF K + : 2.85 ± 0.14 mmol/L (Gomes et al. ). Stocker and colleagues exploring hypernatremia utilized a hand held commercially available device (I‐STAT) to measure CSF Na + , with baseline sodium at 155.3 ± 0.3 mmol/L (Stocker et al.…”

“…Urine electrolyte concentrations typically have a large reported range which is dependent on several factors, but the most prominent is water/food and salt intake (Foss et al 2013;Gomes et al 2017;Osborn et al 2014;Wang et al 2016;Yu et al 2016). As such, most research groups measure 24 h sodium and water balance to help determine water and sodium intake, urine volume and urine sodium excretion (Foss et al 2013;Gomes et al 2017;Osborn et al 2014;Wang et al 2016;Yu et al 2016). Non-24 h urine analysis though can provide insight into progression of disease, including electrolyte imbalance and acid/base disorders (Gray et al 2013;Hamm et al 2015;Waldrop 2008).…”

“…Samples included for analysis can vary, but are not anticipated to be limited to: CSF (Gomes et al. ), blood (Gomes et al. ; Stocker et al.…”

“…We anticipate that this new method will be useful to many research groups investigating SCFA and electrolyte concentrations and those effects on: water and electrolyte homeostasis, stroke, cardiovascular disease, hypertension, metabolic processes, cancer, and ethanol metabolism (Chapp et al 2014), to name a few. Samples included for analysis can vary, but are not anticipated to be limited to: CSF (Gomes et al 2017), blood (Gomes et al 2017;Stocker et al 2015), tissue, cell culture, urine (Foss et al 2013;Lohmeier et al 2005;Osborn et al 2012;Schreihofer et al 1999) and feces. Additionally, complete aqueous extraction removes the need for organic solvents (Richards et al 1975), strong acids/bases (Kamphorst et al 2014;Richards et al 1975;Turnbaugh et al 2006) and ester derivatizing agents (Kamphorst et al 2014;Richards et al 1975;Turnbaugh et al 2006) in SCFA analysis which we envision will drastically increase the reproducibility, and accuracy while reducing variability.…”

“…The necessity in measurement of cations and anions spans a vast array of physiological conditions, ranging from: hypertension (Foss et al 2013;Gomes et al 2017;Kopp et al 2012;Lohmeier et al 2005;Osborn et al 2012;Stocker et al 2015), water and electrolyte homeostasis (Mack et al 1994;Nose et al 1988;Schreihofer et al 1999), stroke (Chung et al 2015;Rappaport et al 1987), and alcohol intoxication (Avery et al 1983;Liamis et al 2000;Tonisson et al 2010) to name a few. Additionally, these traditional techniques exclude small organic ions which can aid in diagnosis and understanding disease progression such as in cancer (Hirschhaeuser et al 2011;Kamphorst et al 2014;Semenza 2008).…”