Cytosolic protein concentration is the primary volume signal in dog red cells.
It is not known whether the activation of Na/H exchange by shrinkage in dog red cells is due to the packing of cell contents or a change in cell configuration. To make this distinction we prepared resealed ghosts that resembled intact cells in hemoglobin concentration and surface area, but had one-third their volume. A shrinkage-induced, amiloride-sensitive Na flux in the ghosts was activated at a much smaller volume in the ghosts than in the intact cells, but at the same concentration (by weight) of dry solids in both preparations. Na/H exchange in ghosts containing a mixture of 40% albumin and 60% hemoglobin (weight/weight) was activated by osmotic shrinkage at a dry solid concentration similar to that of intact cells or of ghosts containing only hemoglobin. We conclude that the process of Na/H exchange activation by cell shrinkage originates with an increase in the concentration of intracellular protein and not with a change in membrane configuration or tension. The macromolecular crowding that accompanies the reduction in cell volume probably alters the activities of key enzymes that in turn modulate the Na/H exchanger.
Colclasure
G C
GC
Department of Medicine, University of North Carolina, Chapel Hill 27514.
Parker
J C
JC
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D003600:Cytosol / Q000737:chemistry*; D004285:Dogs; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000502:physiology; D004911:Erythrocyte Volume / Q000187:drug effects / Q000502:physiology*; D004912:Erythrocytes / Q000737:chemistry* / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis* / Q000502:physiology*; D012709:Serum Albumin / Q000032:analysis* / Q000502:physiology*; D012964:Sodium / Q000493:pharmacokinetics; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D006454:Hemoglobins; D012709:Serum Albumin; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium