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|Title:||Potassium and Sodium Movements Related to Growth State and Malignant Transformation in Cultured Chicken Embryo Cells|
|Author(s):||Johnson, Marcia Anne|
|Department / Program:||Microbiology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Aspects of sodium-potassium pump regulation were examined in growing normal, density-inhibited, and Rous sarcoma virus-transformed (RSV-transformed) chicken embryo fibroblasts and following serum stimulation of quiescent, density-inhibited chicken embryo fibroblasts. Active potassium transport and the associated specific ouabain binding were shown to be dependent on the cellular growth state but unaffected by malignant transformation; potassium influx and ouabain binding values in growing normal and transformed chicken embryo fibroblasts were 1.5 to 1.8-fold greater than in density-inhibited cells. Growing normal and density-inhibited cells were found to have similar potassium contents and RSV-transformed cells a 1.4-fold higher potassium content, as determined by both flame photometry and and isotopic equilibration. Based on the percentage of potassium pool exiting the cell, potassium efflux was found to be 1.3 to 1.5-fold higher in growing normal than RSV-transformed or density-inhibited cells; efflux based on the absolute number of potassium ions is similar in growing normal and transformed cells because of the larger potassium pool in transformed cells.
Serum stimulation of density-inhibited cells resulted in very rapid 1.5 to 1.8-fold increases in ouabain-sensitive potassium influx and lesser 1.4 to 1.5-fold increases in potassium efflux and efflux-blocked sodium influx. Potassium influx stimulation was maximal after addition of five to twenty percent calf serum and was unaffected by cycloheximide inhibition of protein synthesis. Reflecting the slightly greater stimulation of potassium influx versus potassium efflux, potassium ion levels were ten to fifteen percent higher in serum-stimulated compared to unstimulated cells. Specific ouabain binding levels in stimulated and unstimulated control cells were initially similar, however by four hours after stimulation a forty to fifty percent increase in specific ouabain binding was observed. Incubation with ouabain was found to inhibit later serum-stimulated hexose uptake and thymidine incorporation; this blockage may be a consequence of subnormal potassium levels rather than ouabain inhibition of serum-stimulated potassium influx. Both the observed serum stimulation of sodium influx in the absence of potassium influx stimulation (using ouabain blockage of the sodium-potassium pump) and the small change in cellular potassium content following serum stimulation suggest that serum-stimulated potassium influx changes do not act as a primary "trigger" for mitogen-activated cellular changes.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
|Date Available in IDEALS:||2014-12-14|