Increase of Calcium Levels at Interphase in NIH 3T3 Cells

The fluorescent calcium ion indicator dye Fluo-3 and DNA-binding dye Hoechst 33342 were employed to determine, in a quantitative microspectrofluorometric study, the intracellular calcium ion concentration (Ca~(2+)]_i) and the DNA content of individual living NIH3T3 cells. The well-separated excitation and emission properties of these dyes allowed us to establish for each cell both the phase of the cell cycle using DNA content and Ca~(2+)]_i. We found that the transition from G_1, through S, to the G_2 phase is accompanied by a two-fold increase in Ca~(2+)]_i. The Ca~(2+)]_i was inhomologous in each phase of the interphase (G_1, S and G_2) although Ca~(2+)]_i in the S and G_2 phases was never lower than certain threshold values in the G_1 and S phases respectively. Ca~(2+)]_i in G_0 cells was lower than that in G_2 cells. These changes in Ca~(2+)]_i suggest that Ca~(2+)]_i may be an import regulator of cell cycle progression.

Increase of Calcium Levels at Interphase in NIH 3T3 Cells

The fluorescent calcium ion indicator dye Fluo-3 and DNA-binding dye Hoechst 33342 were employed to determine, in a quantitative microspectrofluorometric study, the intracellular calcium ion concentration (Ca~(2+)]_i) and the DNA content of individual living NIH3T3 cells. The well-separated excitation and emission properties of these dyes allowed us to establish for each cell both the phase of the cell cycle using DNA content and Ca~(2+)]_i. We found that the transition from G_1, through S, to the G_2 phase is accompanied by a two-fold increase in Ca~(2+)]_i. The Ca~(2+)]_i was inhomologous in each phase of the interphase (G_1, S and G_2) although Ca~(2+)]_i in the S and G_2 phases was never lower than certain threshold values in the G_1 and S phases respectively. Ca~(2+)]_i in G_0 cells was lower than that in G_2 cells. These changes in Ca~(2+)]_i suggest that Ca~(2+)]_i may be an import regulator of cell cycle progression.