Skin Sodium and Blood Pressure Regulation

Hypertension is a major public health concern due to its high prevalence and increased risk of cardiovascular disease and mortality. Complex traits resulting from both genetic and environmental factors affect the development of hypertension. Among environmental factors, a high salt diet is an important cause for hypertension. Humans show a heterogeneous blood pressure (BP) response to sodium intake. Although the precise mechanisms for the association between salt sensitivity and hypertension have not been fully elucidated, renal sodium handling has been considered to play a pivotal role. However, this conventional view has recently been challenged in that a third compartment, namely, skin may have a role in the regulation of sodium homeostasis. Skin is comprised of a significant portion of interstitium, which is a major extracellular fluid compartment, and its complex capillary network regulates body temperature and skin perfusion. Growing evidence indicates that local regulatory action of cutaneous blood flow as well as salt and water metabolism is associated with systemic BP control. Previous experimental studies have shown that dietary salt loading resulted in nonosmotic sodium accumulation via glycosaminoglycans and lymphatics embedded in the skin that were mediated by several endogenous factors and attenuated an increase in BP. Studies in humans have also suggested that the skin serves as a buffer system for sodium storage and that skin sodium contributes to salt sensitivity and hypertension. Thus, skin sodium storage provides the possibility of being an additional buffering system in response to salt loading and concomitant BP changes in humans.