Regulation of cell volume by the osteosarcoma cell line UMR-106-01.
Determination of cell volume by an electronic cell-sizing technique was used to study the role of ion transporters in cell volume regulation by the osteosarcoma cell line UMR-106-01. Swelling the cells in hypotonic medium was followed by regulatory volume decrease (RVD). The rate of RVD was strongly dependent on the subpassage used and increased with increasing subpassages. Swelling-evoked changes in cytosolic free Ca2+ ([Ca2+]i) did not account for this behavior, since it was similar in cells from all subpassages. Increasing plasma membrane K+ permeability with valinomycin resulted in a similar rate of RVD in cells from different subpassages, suggesting increased K+ channel activity or other electrogenic transporter with increased subpassages. In contrast, the mechanisms responsible for regulatory volume increase (RVI) were fully active in cells from all subpassages. Increasing medium osmolarity of cells bathed in isotonic medium induced slow and incomplete RVI. In addition, shrinking cells exposed to hypotonic medium before completion of RVD resulted in impaired RVI. Effective RVI could be observed only after completion of RVD of cells exposed to hypotonic medium. Removal of extracellular Na+ or K+ completely blocked RVI, whereas removal of external Cl- partially blocked RVI. The effect of K+ removal probably reflects in part inhibition of Na-K-2Cl cotransport and in part inhibition of the Na+ pump.(ABSTRACT TRUNCATED AT 250 WORDS)
Khademazad
M
M
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.
Zhang
B X
BX
Loessberg
P
P
Muallem
S
S
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D003600:Cytosol / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D007038:Hypotonic Solutions; D007700:Kinetics; D009994:Osmolar Concentration; D012516:Osteosarcoma / Q000503:physiopathology*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D007038:Hypotonic Solutions; D015221:Potassium Channels; D014634:Valinomycin; D000584:Amiloride; D005665:Furosemide; D011494:Protein Kinases; D011188:Potassium; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine