Cerebral osmotic adaptation to severe hyponatremia

Changes in brain water, sodium-plus-potassium (Na + K) content, and three organic solutes – inositol, glutamine, and taurine – two and seven days after the onset of severe hyponatremia (plasma sodium concentration of less than 110 meq/L). The numbers at the bottom represent the baseline values. The return of brain water toward normal at day 7 is due to loss of sodium, potassium, and the organic solutes (called osmolytes). Although the absolute osmolyte loss is less than that of sodium plus potassium, the fractional loss is much greater – 36 of 60 or 60 percent versus 60 of 670 or less than 10 percent. Preferential osmolyte loss has the added advantage of not interfering with protein function within the cells.