We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Isoosmotic shrinkage by self-stimulated outward Na-K-Cl cotransport in quail erythrocytes.
- Authors
Lou, Josè M.; Garay, Ricardo P.; Gimenez, Ignacio; Escanero, Jesus F.; Alda, Josè O.
- Abstract
In mammalian erythrocytes, outward fluxes by the Na-K-Cl cotransporter NKCC have been clearly characterized, but NKCC fluxes are small and their physiological role, if any, is poorly understood. Avian erythrocytes are nucleated cells, in which a physiologically relevant NKCC acts as a cell volume regulator. Therefore, we further investigated outward cotransport and its relation to cell volume by using quail erythrocytes. Unlike human or rat erythrocytes, quail erythrocytes exhibit outward cotransport fluxes: (1) of high magnitude [maximal rate of bumetanide-sensitive Li+ efflux=12.3±1.1 mmol (l cells·h)–1, mean ±SEM, n=23] and (2) strongly stimulated by hyperosmotic media (by 100–200% in 500 mosmol/l media). Na+- or Li+-loaded quail erythrocytes exhibited rapid cell shrinkage when incubated in K+-free media. Thus, cell volume remained stationary up to 5–10 min and then started to shrink. Shrinkage was first slow, but progressively accelerated, finally reaching a new stationary state where cell volume had decreased by about 20%. Such rapid cell shrinkage was fully inhibited by bumetanide and was associated with outward cotransport stimulation (self-stimulated or an auto-catalytic process, i.e. a reaction stimulated by its product). External K+ reduced all these phenomena, but significant cell shrinkage was still observed at an external K+ concentration of 2.8 mM. K+ removal failed to stimulate outward cotransport in hypotonic media (250 mosmol/l). Finally, reincubation of shrunken erythrocytes in physiological saline revealed that inward cotransport was stimulated more than outward cotransport. In conclusion, isoosmotic hypokalaemia drives a rapid shrinkage of quail erythrocytes, due to auto-catalytic net outward cotransport stimulation. Whether this is an experimental curiosity or indicates that outward cotransport can have some physiological role deserves further investigation.
- Subjects
SODIUM cotransport systems; ACTIVE biological transport; PHYSIOLOGICAL transport of sodium; POTASSIUM channels; CHLORIDE channels; ERYTHROCYTES; BLOOD cells; CELL membranes
- Publication
Pflügers Archiv: European Journal of Physiology, 2003, Vol 447, Issue 1, p64
- ISSN
0031-6768
- Publication type
Article
- DOI
10.1007/s00424-003-1132-x