Beyond The Current Paradigm: Recent Advances in The Understanding of Sodium Handling – Guest Editors: Stanley Shaldon and Joerg Vienken: Water‐Free Sodium Accumulation

Abstract

The widely accepted concept of body fluid and electrolyte homeostasis is that Na(+) is restricted mainly to the extracellular fluid and K(+) to the intracellular space, where both ions act to hold water and thereby control the extracellular and intracellular fluid volume by their osmotic activity. Na(+) accumulation thus inevitably leads to water retention. The constancy of the extracellular volume is the task of the kidneys, which control the total body Na(+) content. More recent data have questioned this traditional view, suggesting that large amounts of Na(+) can be accumulated without accompanying water retention by osmotically inactive Na(+) retention, or by osmotically neutral Na(+)/K(+) exchange. Besides the control of the body Na(+) content by the kidneys, redistribution of body electrolytes hence provides an extrarenal regulatory alternative in the maintenance of body fluid volume and blood pressure control.

Use of Online Conductivity Monitoring to Study Sodium Mass Balance in Chronic Haemodialysis Patients: Prospects for Treatment Individualisation

“…The relationship between sodium and BP in HD patients is more complicated than mere volume expansion. Previous models of sodium kinetics assume a two-compartment model, but Titze [17] has recently proposed an alternative threecompartment model by showing that sodium can accumulate in the vascular wall without volume expansion, which might explain the lag in improved BP control seen after dry weight reduction in patients treated with longslow HD [17,32,33] .…”

“…This makes it possible for patients to load sodium during dialysis, despite dialysate sodium concentration being lower than the predialysis plasma sodium concentration (commonly termed 'low' dialysate sodium concentration) [15,16] . More recently, the non-osmotic storage of sodium in skin and other tissues has been described and this may further allow dissociation of sodium and water handling [17] . Though the effects of this may be negligible over a single HD session, the potential of this reservoir of sodium ions to buffer sodium transport over a longer period and influence BP and IDWG has not been fully elucidated.…”

Immune cells control skin lymphatic electrolyte homeostasis and blood pressure

“…It assumes isosmolarity of body fluids among the bodily compartments (2). Along with others (4-7), we (8)(9)(10)(11)(12)(13)(14) showed earlier that electrolytes are distributed in a more complex 3-compartment model, in which intravascular and the interstitial fluids do not equilibrate as readily as believed (15,16). We underscored the importance of Na + binding to negatively charged proteoglycans in the skin, the largest organ with the most extracellular space (8,11).…”

Increase in Body Na + /Water Ratio Is Associated With Cerebral Aneurysm Formation in Oophorectomized Rats

“…Titze,18 who suggested that Na + handling during increased dietary salt intake is more complex, highlighting the dynamic role of the dermal interstitium as a reservoir that can buffer the impact of Na + accumulation on the intravascular volume and blood pressure, proposed that accumulated water-free Na + is associated with hypertension. However, the relationship between vascular injury and water-free Na + remains to be addressed.…”