AJP - Cell Physiology, Vol 252, Issue 2 C138-C152, Copyright © 1987 by American Physiological Society
Calcium, cell shrinkage, and prolytic state of human red blood cells
L. M. Crespo, T. S. Novak and J. C. Freedman
The effects of intracellular calcium, or Cac, on the Na permeability of
human red blood cells were examined during 3-h incubations with the Ca
ionophore A23187 and varied external Ca, Cao. Above 3 microM Cao, Nac
increased significantly as ATP decreased. Maintenance of normal ATP with
vanadate did not prevent the gain of Nac. Similar amounts of Nac were
gained in 3 h by ouabain-treated cells exposed to the K ionophore
valinomycin or by cells osmotically shrunken. Cells shrunken with sucrose
also exhibited partial loss of Kc. When the cells with increased Nac were
subsequently transferred to Na-free, high-K medium, the Nac and Kc that had
changed slowly over 3 h returned toward normal within 10 min. The
development of irreversible high cation permeability in shrunken cells was
not prevented by a variety of transport inhibitors. These observations and
cell volume distributions suggest that prolonged shrinkage induces a
subpopulation of cells to become highly cation permeable, or "prolytic".
The major effect of Cac on Na permeability appears to be an indirect
consequence of cell shrinkage due to KCl loss.
