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Voltage-activated cation transport in human erythrocytes
J A Halperin1, C Brugnara, M T Tosteson
1Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
The American Journal of Physiology
|November 1, 1989
Summary
Altering human erythrocyte membrane potential increases sodium (Na), potassium (K), and calcium (Ca) ion permeability. This voltage-dependent ion conductance, partially inhibited by ruthenium red, affects cell volume and ion gradients.
Area of Science:
- Cellular Physiology
- Membrane Biophysics
- Ion Transport
Background:
- The erythrocyte membrane potential is crucial for regulating ion transport.
- Understanding voltage-dependent ion channels is key to cellular function.
Purpose of the Study:
- To investigate the impact of membrane potential on human erythrocyte permeability to Na, K, and Ca ions.
- To characterize the voltage-dependent ion conductance and its modulators.
Main Methods:
- Manipulating membrane potential using K concentration gradients with valinomycin.
- Altering ion gradients with permeant anions (nitrate) and specific inhibitors (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid).
- Measuring ion fluxes (influx, efflux, net flux) and cell volume changes.
Main Results:
- Increased Na and K influx, efflux, and net flux when membrane potential shifted from negative to positive.
- Observed net cation loss and cell shrinkage independent of chemical gradients.
- Demonstrated voltage-dependent Ca influx, significantly inhibited by ruthenium red.
- Voltage-dependent conductance persisted after returning to negative potentials.
Conclusions:
- Human erythrocyte membrane potential directly influences Na, K, and Ca permeability.
- A voltage-dependent cation conductance mechanism exists in erythrocytes.
- Ruthenium red partially inhibits voltage-dependent Na/K conductance and almost completely inhibits voltage-activated Ca influx.