Cell volume regulation by skate erythrocytes: role of potassium.
The role of K transport during cell volume regulation in response to extracellular osmolality, protein kinase C activation, and cellular Ca was examined in skate (Raja erinacea) red blood cells (RBC). Reduction of medium osmolality from 960 to 660 mosmol/kgH2O had no effect on K uptake or efflux despite a 25% increase in cell volume. Further reduction to 460 mosmol/kgH2O caused K uptake to double and K efflux to triple resulting in net K loss. Net K efflux in 460 mosmol/kgH2O medium was correlated with the presence of a regulatory volume decrease, which was sensitive to the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and insensitive to chloride replacement. K-K exchange was absent in both isotonic and hypotonic media. Treatment with the Ca ionophore A23187 in the presence of Ca had no effect on either cell volume or K efflux in isotonic medium, indicating the absence of Ca-activated K transport. In contrast, phorbol ester treatment caused cell volume, Na content, and proton and K efflux to increase. Consistent with activation of Na-H exchange, phorbol ester effects were inhibited by dimethylamiloride. This study constitutes the first demonstration of volume-sensitive K transport in RBC from the most primitive vertebrate studied to date.
Dickman
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Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 22710.
Goldstein
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D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D000001:Calcimycin / Q000494:pharmacology; D004555:Electric Fish / Q000502:physiology*; D004912:Erythrocytes / Q000166:cytology*; D007038:Hypotonic Solutions; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D012860:Skates, Fish / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007038:Hypotonic Solutions; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000001:Calcimycin; D013755:Tetradecanoylphorbol Acetate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium