Induction of 86Rb Fluxes by Ca2+ and volume changes in thymocytes and their isolated membranes

S. Grinstein, S. Cohen, B. Sarkadi, A. Rothstein

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27 Citations (Scopus)

Abstract

Cell swelling and elevated intracellular Ca2+ increase K+ permeability in lymphocytes. Experiments were performed to test whether these effects can also be elicited in isolated plasma membrane vesicles. Rabbit thymocytes, used as a source of membrane vesicles, were found to regain their volume after swelling in hypotonic, low‐K+ media. This regulatory volume decrease (RVD) was inhibited by quinine and trifluoperazine, but not affected by ouabain. Both efflux and uptake of K+ (86Rb) were stimulated by hypotonicity. Addition of A23187 plus Ca2+ also increased 86Rb fluxes. Ca2+ ‐ and volume‐induced 86Rb fluxes were also studied in isolated membranes. A plasma membrane‐rich vesicle fraction, enriched over 11‐fold in 5′‐nucleotidase, was isolated from thymocytes. The vesicles were about 35% inside‐out and trapped 86Rb in an osmotically active compartment of ∼1.3 μl/mg protein. Equilibrium exchange fluxes of 86Rb in the vesicles were unaffected by Ca2+ with or without A23187. Calmodulin had no effect on 86Rb permeability but stimulated ATP‐dependent Ca2+ accumulation. Hypotonic swelling increased both uptake and efflux of 86Rb from vesicles. However, this increase was not blocked by either quinine or trifluoperazine, was not specific for K+ (86Rb), and is probably unrelated to RVD. It is concluded that components essential for the volume‐ and Ca2+‐induced changes in K+ permeability are lost or inactivated during membrane isolation. An intact cytoarchitecture may be required for RVD.

Original languageEnglish
Pages (from-to)352-362
Number of pages11
JournalJournal of Cellular Physiology
Volume116
Issue number3
DOIs
Publication statusPublished - Sep 1983

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology

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