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Regulatory volume decrease in HL-60 cells: importance of rapid changes in permeability of Cl- and organic solutes
1Department of Biophysics, University of Rochester Medical Center, New York 14642.
The American Journal of Physiology
|October 1, 1994
Summary
Human HL-60 cells regulate cell volume decrease (RVD) via potassium (K+) and chloride (Cl-) efflux through distinct membrane channels. These pathways differ from those in other cell types, with K+ efflux being rate-limiting.
Area of Science:
- Cellular physiology
- Membrane transport
- Biophysics
Background:
- Regulatory volume decrease (RVD) is a crucial cellular response to hypotonic stress.
- Understanding the ion transport mechanisms underlying RVD is essential for cell volume regulation.
- Previous studies identified RVD mechanisms in other cell types, but HL-60 cells present unique characteristics.
Purpose of the Study:
- To elucidate the specific ion fluxes and membrane transport pathways involved in the RVD response of human promyelocytic leukemic HL-60 cells.
- To characterize the properties of the membrane potential and ion permeabilities during RVD.
- To compare the RVD mechanism in HL-60 cells with those previously described in other cell lines.
Main Methods:
- Inhibitor studies and isotope flux techniques were employed to investigate ion movement.
- Equilibration techniques were used to assess membrane potential and ion permeabilities.
- A diffusion kinetic model was applied to analyze 86Rb+ and 36Cl- fluxes under varying tonicities.
- Gramicidin treatment was used to probe the rate-limiting steps in RVD.
Main Results:
- HL-60 cell RVD primarily involves K+ and Cl- efflux through separate, pharmacologically distinct membrane channels.
- Chloride permeability (PCl) significantly increases with decreasing tonicity, exceeding potassium permeability (PK) at 50% isotonicity.
- Potassium (K+) efflux is identified as the rate-limiting step in the RVD process.
- The combined efflux of K+ and Cl- is insufficient to fully account for volume recovery, suggesting the involvement of other organic osmolytes.
Conclusions:
- The RVD mechanism in HL-60 cells relies on distinct K+ and Cl- conductive pathways, differing from those in lymphocytes and Ehrlich ascites tumor cells.
- Potassium permeability is the rate-limiting factor for RVD in these cells.
- HL-60 cell RVD involves the efflux of K+ and Cl- along with other organic osmolytes to achieve volume regulation.