FLOW CYTOMETRIC APPLICATIONS OF SULFORHODAMINE-101 AS A FLUORESCENT STAIN FOR TOTAL CELLULAR PROTEIN

In this paper, the use of Sulforhodamine 101 (SR 101; C.I. 14318) as a fluorescent stain for now cytometric determinations of total cellular protein (TCP) is described. Flow cytometric quantification of TCP flu orescence can provide a valuable analytical parameter for assessing bo th changes occurring in overall cellular protein content, such as in r esponse to blast transformation, and heterogeneity in cellular size wi thin a specimen, such as a tumor, Very little information is available in the literature pertaining to the use of SR 101 as a protein stain. Like fluorescein isothiocyanate (FITC), SR 101 can be excited at 488 nm; however, it binds ionically and has an emission maximum at 600 nm, which is advantageous in certain staining and filter combinations. In this report, the utility of SR 101 staining is demonstrated using pok eweed mitogen-stimulated lymphocytes and cycloheximide- and dimethylsu floxide-treated cells. Single, two- and three-color now cytometric app lications are possible, using SR 101 in combination with 4',6-diamidin o-2-phenylindole (DAPI) and/or FITC.