New system for blood pressure regulation uncovered
Every day, we learn more and more about the metabolism of salt and mechanism of its role in maintaining balance or homeostasis within our circulatory system. Some of the most interesting work continues to come from a Europe-wide collaborative group based in Germany. Their latest work entitled, “Macrophages regulate salt-dependent volume and blood pressure by a vascular endothelial growth factor-C–dependent buffering mechanism,” was just published online by Nature Medicine .
This new data provides valuable insights into the role of the mononuclear phagocyte system (MPS) cell and lymphatic function in the context of maintaining intracellular Na+ homeostasis. Cells of the mononuclear phagocyte system (MPS) are found in large numbers in every organ of the body, where they contribute to innate and acquired immunity and fluid balance. When rats are fed high salt diets, the extra accumulation of sodium ions that occurs in excess of compensating water results in local hypertonicity or increased pressures that provokes a tissue-specific regulatory cascade, with the macrophages releasing vascular endothelial growth factor-C (VEGF-C) which acts protective protein to maintain a constant intracellular volume. This mechanism then restructures the existing lymph capillary network and to manage this increased pressure.
The researchers conclude that the complex MPS-derived secretion of VEGF-C in states of sodium-induced intracellular hypertonicity functions to moderates blood pressure.
Their findings move the prevailing view of the salt volume–blood pressure relationship from a simpler two-compartment model to a more dynamic three-compartment model in which the interstitial (intracellular) spaces in tissues feature as a separately regulated space that also relies on tissue-specific mechanisms to maintain internal osmo- or pressure regulation.
While we caution that this work was done with rats -- and at experimentally huge salt intake levels to demonstrate the mechanism -- and, therefore, has no human health policy implications at this point, the study usefully reveals how complex a system we have evolved to manage and balance all components of our diet.
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