Uptake Of H2O Research Articles

Volume regulation by Amphiuma red blood cells. The membrane potential and its implications regarding the nature of the ion-flux pathways.

After osmotic perturbation, the red blood cells of Amphiuma exhibited a volume-regulatory response that returned cell volume back to or toward control values. After osmotic swelling, cell-volume regulation (regulatory volume decrease; RVD) resulted from net cellular loss of K, Cl, and osmotically obliged H2O. In contrast, the volume-regulatory response to osmotic shrinkage (regulatory volume increase; RVI) was characterized by net cellular uptake of Na, Cl, and H2O. The net K and Na fluxes characteristic of RVD and RVI are increased by 1-2 orders of magnitude above those observed in studies of volume-static control cells. The cell membrane potential of volume-regulating and volume-static cells was measured by impalement with glass microelectrodes. The information gained from the electrical and ion-flux studies led to the conclusion that the ion fluxes responsible for cell-volume regulation proceed via electrically silent pathways. Furthermore, it was observed that Na fluxes during RVI were profoundly sensitive to medium [HCO3] and that during RVI the medium becomes more acid, whereas alkaline shifts in the suspension medium accompany RVD. The experimental observations are explained by a model featuring obligatorily coupled alkali metal-H and Cl-HCO3 exchangers. The anion- and cation-exchange pathways are separate and distinct yet functionally coupled via the net flux of H. As a result of the operation of such pathways, net alkali metal, Cl, and H2O fluxes proceed in the same direction, whereas H and HCO3 fluxes are cyclic. Data also are presented that suggest that the ion-flux pathways responsible for cell-volume regulation are not activated by changes in cell volume per se but by some event associated with osmotic perturbation, such as changes in intracellular pH.

800 MUSCLE ELECTROLYTE METABOLISM IN MONKEYS WITH EXPERIMENTAL SALMONELLA SEPSIS

Altered electrolyte metabolism is reflected in changes in serum concentration and total balance in patients with infectious diseases. A sub-lethal experimental sepsis was induced with 108 S. typhimurium organism administered intravenously to determine what role muscle plays in these changes. Muscle samples were obtained by needle biopsy. During the 3 day febrile phase, K wasting was evident in muscle, serum, and in urine. This returned to normal after the lysis of fever. The metabolism of Na and water was independent from that of K. During the febrile period, muscle H2O increased, and muscle and serum Na increased. Although antidiuresis persisted throughout the first 6 days of illness, an Na diuresis occurred during the period of fever. With the lysis of fever, renal Na retention occurred, muscle Na and H2O increased to twice the basal levels and serum Na fell 20 mEq/L. It can be concluded that muscle uptake of Na and H2O plays a significant role in the modulation of serum concentrations and the renal filtered load in experimental sepsis. K depletion was secondary to renal wasting, K loss was in excess of nitrogen loss from muscle. However, studies with the Electron Microprobe for direct determination of intracellular concentration indicate that intracellular dilutions play a major role in the reduction of cellular K during infection.Support:NIH-RR-00188,NASA NGR 9-12728,U.S. Army DAMD-17-74-C-4079