POSSIBLE DEPOSITION OF OSMOTICALLY INACTIVE SODIUM IN HEALTHY VOLUNTEERS DURING PROLONGED BED REST

摘要

The physiological role of sodium ion in human organism is very important. As the basic ion in extracellular fluid, Na determines osmolality and volumes of compartments of the body fluids thus controlling the acid-base balance, blood pressure, and genesis of the membrane and action potentials. It's well known that sodium, except of its turnover between body and surroundings, can be stowed in conjunctive tissue, where the quantities of metabolizable and deposable Na in organism are approximately in a 7:3 ratio. The purpose of this work was to study the hypothesis for non-ion sodium deposition in human organism by way of separating the volume and osmolality regulation during prolonged bed rest. Totally it was analyzed the individual subjects' dynamics of sodium and water balance in the 120- to 360-day head down tilt bed rest experiments (HDT BR) performed with participation of 45 health volunteers. We concluded, that non-osmotic regulation of Na deposition can enter onto the scene as in response to sharp deviations from the normal salt intake so on a background of normal salt consumption with food. Prevalence of osmotic or non-osmotic Na regulation in organism may depend not only on external factors, but also individual characteristics. Also, during the bed rest experiments all volunteers demonstrated more or less extended periods of non-osmotic Na deposition.