title: Intracellular ionic changes in normal and transformed human fibroblasts after extracellular Ca2+ deprivation.
abstract: The lowering of extracellular Ca2+ concentration in the growth medium reversibly blocks normal, but not SV40-transformed WI38 diploid fibroblasts in the early G1/G0 phase of the cell cycle. This growth response is characterized by specific changes in ionic content and transport. Ca2+ deprivation (0.03 mM) has little effect on the K+ content of either normal or transformed cells. Na+ content, however, is increased nearly 2-fold in the normal cells. This increase is presumably due to a 3-fold increase in unidirectional Na+ influx in Ca2+-deprived cells. The increased intracellular Na+ also gives rise to a nearly 3-fold enhancement of the active (ouabain-sensitive) Na+ efflux. Ca2+ deprivation causes only slight increases in Na+ influx, ouabain-sensitive Na+ efflux and intracellular Na+ in the transformed cell. In contrast, the transformed cells lose nearly 60% of their intracellular Ca2+ on deprivation, whereas normal WI38 cells lose only 10%. The data suggest that the growth arrest exhibited by the normal cell but not the transformed cell may be related to different membrane-transport and permeability changes in response to Ca2+ deprivation.
mesh_terms: D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D002472:Cell Transformation, Viral; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D012964:Sodium; D011188:Potassium; D002118:Calcium