Abstract
Quantitative, correlated determinations of DNA, RNA, and protein, as well as RNA to DNA and RNA to protein ratios, were performed on three-color stained cells using a multiwavelength-excitation flow cytometer. DNA-bound Hoechst 33342 (blue), protein-fluorescein isothiocyanate (green), and RNA-bound pyronin Y (red) fluorescence measurements were correlated as each stained cell intersected three spatially separated laser beams. The analytical scheme provided sensitive and accurate fluorescence determinations by minimizing the effects of overlap in the spectral characteristics of the three dyes. Computer analysis was used to generate two-parameter contour density profiles as well as to obtain numerical data for subpopulations delineated on the basis of cellular DNA content. Such determinations allowed for analysis of RNA to DNA and RNA to protein ratios for cells within particular regions of the cell cycle. The technique was used to study the interrelationship of DNA, RNA, and protein contents in exponentially growing Chinese hamster ovary cells as well as in cell populations progressing the cell cycle after release from arrest in G1 phase. The sensitivity of the method for early detection of conditions of unbalanced growth is demonstrated in the comparison of the differential effects of the cycle-perturbing agent, adriamycin, on cells treated either during exponential growth or while reversibly arrested in G1 phase.